Provided by: backuppc_2.1.2-2ubuntu5_all bug

BackupPC Introduction

       This documentation describes BackupPC version 2.1.2, released on 5 Sep
       2005.

       Overview

       BackupPC is a high-performance, enterprise-grade system for backing up
       Unix, Linux and WinXX PCs, desktops and laptops to a server’s disk.
       BackupPC is highly configurable and easy to install and maintain.

       Given the ever decreasing cost of disks and raid systems, it is now
       practical and cost effective to backup a large number of machines onto
       a server’s local disk or network storage.  For some sites this might be
       the complete backup solution.  For other sites additional permanent
       archives could be created by periodically backing up the server to
       tape.

       Features include:

       ·   A clever pooling scheme minimizes disk storage and disk I/O.
           Identical files across multiple backups of the same or different PC
           are stored only once (using hard links), resulting in substantial
           savings in disk storage and disk writes.

       ·   Optional compression provides additional reductions in storage
           (around 40%).  The CPU impact of compression is low since only new
           files (those not already in the pool) need to be compressed.

       ·   A powerful http/cgi user interface allows administrators to view
           log files, configuration, current status and allows users to
           initiate and cancel backups and browse and restore files from
           backups.

       ·   The http/cgi user interface has internationalization (i18n)
           support, currently providing English, French, German, Spanish,
           Italian and Dutch.

       ·   No client-side software is needed. On WinXX the standard smb
           protocol is used to extract backup data. On linux or unix clients,
           rsync or tar (over ssh/rsh/nfs) is used to extract backup data.
           Alternatively, rsync can also be used on WinXX (using cygwin), and
           Samba could be installed on the linux or unix client to provide smb
           shares).

       ·   Flexible restore options.  Single files can be downloaded from any
           backup directly from the CGI interface.  Zip or Tar archives for
           selected files or directories from any backup can also be
           downloaded from the CGI interface.  Finally, direct restore to the
           client machine (using smb or tar) for selected files or directories
           is also supported from the CGI interface.

       ·   BackupPC supports mobile environments where laptops are only
           intermittently connected to the network and have dynamic IP
           addresses (DHCP).  Configuration settings allow machines connected
           via slower WAN connections (eg: dial up, DSL, cable) to not be
           backed up, even if they use the same fixed or dynamic IP address as
           when they are connected directly to the LAN.

       ·   Flexible configuration parameters allow multiple backups to be
           performed in parallel, specification of which shares to backup,
           which directories to backup or not backup, various schedules for
           full and incremental backups, schedules for email reminders to
           users and so on.  Configuration parameters can be set system-wide
           or also on a per-PC basis.

       ·   Users are sent periodic email reminders if their PC has not
           recently been backed up.  Email content, timing and policies are
           configurable.

       ·   BackupPC is Open Source software hosted by SourceForge.

       Backup basics

       Full Backup
           A full backup is a complete backup of a share. BackupPC can be
           configured to do a full backup at a regular interval (typically
           weekly).  BackupPC can be configured to keep a certain number of
           full backups.  Exponential expiry is also supported, allowing full
           backups with various vintages to be kept (for example, a settable
           number of most recent weekly fulls, plus a settable number of older
           fulls that are 2, 4, 8, or 16 weeks apart).

       Incremental Backup
           An incremental backup is a backup of files that have changed (based
           on their modification time) since the last successful full backup.
           For SMB and tar, BackupPC backups all files that have changed since
           one hour prior to the start of the last successful full backup.
           Rsync is more clever: any files whose attributes have changed (ie:
           uid, gid, mtime, modes, size) since the last full are backed up.
           Deleted, new files and renamed files are detected by Rsync
           incrementals.  In constrast, SMB and tar incrementals are not able
           to detect deleted files, renamed files or new files whose
           modification time is prior to the last full dump.

           BackupPC can also be configured to keep a certain number of
           incremental backups, and to keep a smaller number of very old
           incremental backups.  (BackupPC does not support multi-level
           incremental backups, although it will in a future version.)

           BackupPC’s CGI interface "fills-in" incremental backups based on
           the last full backup, giving every backup a "full" appearance.
           This makes browsing and restoring backups easier.

       Partial Backup
           When a full backup fails or is canceled, and some files have
           already been backed up, BackupPC keeps a partial backup containing
           just the files that were backed up successfully.  The partial
           backup is removed when the next successful backup completes, or if
           another full backup fails resulting in a newer partial backup.  A
           failed full backup that has not backed up any files, or any failed
           incremental backup, is removed; no partial backup is saved in these
           cases.

           The partial backup may be browsed or used to restore files just
           like a successful full or incremental backup.

           With the rsync transfer method the partial backup is used to resume
           the next full backup, avoiding the need to retransfer the file data
           already in the partial backup.

       Identical Files
           BackupPC pools identical files using hardlinks.  By "identical
           files" we mean files with identical contents, not necessary the
           same permissions, ownership or modification time.  Two files might
           have different permissions, ownership, or modification time but
           will still be pooled whenever the contents are identical.  This is
           possible since BackupPC stores the file meta-data (permissions,
           ownership, and modification time) separately from the file
           contents.

       Backup Policy
           Based on your site’s requirements you need to decide what your
           backup policy is.  BackupPC is not designed to provide exact re-
           imaging of failed disks.  See Limitations for more information.
           However, the addition of tar transport for linux/unix clients, plus
           full support for special file types and unix attributes in v1.4.0
           likely means an exact image of a linux/unix file system can be
           made.

           BackupPC saves backups onto disk. Because of pooling you can
           relatively economically keep several weeks of old backups.

           At some sites the disk-based backup will be adequate, without a
           secondary tape backup. This system is robust to any single failure:
           if a client disk fails or loses files, the BackupPC server can be
           used to restore files. If the server disk fails, BackupPC can be
           restarted on a fresh file system, and create new backups from the
           clients. The chance of the server disk failing can be made very
           small by spending more money on increasingly better RAID systems.
           However, there is still the risk of catastrophic events like fires
           or earthquakes that can destroy both the BackupPC server and the
           clients it is backing up if they are physically nearby.

           Some sites might choose to do periodic backups to tape or cd/dvd.
           This backup can be done perhaps weekly using the archive function
           of BackupPC.

           Other users have reported success with removable disks to rotate
           the BackupPC data drives, or using rsync to mirror the BackupPC
           data pool offsite.

       Resources

       BackupPC home page
           The BackupPC Open Source project is hosted on SourceForge.  The
           home page can be found at:

               http://backuppc.sourceforge.net

           This page has links to the current documentation, the SourceForge
           project page and general information.

       SourceForge project
           The SourceForge project page is at:

               http://sourceforge.net/projects/backuppc

           This page has links to the current releases of BackupPC.

       BackupPC FAQ
           BackupPC has a FAQ at <http://backuppc.sourceforge.net/faq>.

       Mail lists
           Three BackupPC mailing lists exist for announcements
           (backuppc-announce), developers (backuppc-devel), and a general
           user list for support, asking questions or any other topic relevant
           to BackupPC (backuppc-users).

           The lists are archived on SourceForge and Gmane.  The SourceForge
           lists are not always up to date and the searching is limited, so
           Gmane is a good alternative.  See:

               http://news.gmane.org/index.php?prefix=gmane.comp.sysutils.backup.backuppc
               http://sourceforge.net/mailarchive/forum.php?forum_id=503

           You can subscribe to these lists by visiting:

               http://lists.sourceforge.net/lists/listinfo/backuppc-announce
               http://lists.sourceforge.net/lists/listinfo/backuppc-users
               http://lists.sourceforge.net/lists/listinfo/backuppc-devel

           The backuppc-announce list is moderated and is used only for
           important announcements (eg: new versions).  It is low traffic.
           You only need to subscribe to one of backuppc-announce and
           backuppc-users: backuppc-users also receives any messages on
           backuppc-announce.

           The backuppc-devel list is only for developers who are working on
           BackupPC.  Do not post questions or support requests there.  But
           detailed technical discussions should happen on this list.

           To post a message to the backuppc-users list, send an email to

               backuppc-users@lists.sourceforge.net

           Do not send subscription requests to this address!

       Other Programs of Interest
           If you want to mirror linux or unix files or directories to a
           remote server you should consider rsync, <http://rsync.samba.org>.
           BackupPC now uses rsync as a transport mechanism; if you are
           already an rsync user you can think of BackupPC as adding efficient
           storage (compression and pooling) and a convenient user interface
           to rsync.

           Unison is a utility that can do two-way, interactive,
           synchronization.  See <http://www.cis.upenn.edu/~bcpierce/unison>.

           Three popular open source packages that do tape backup are Amanda
           (<http://www.amanda.org>), afbackup
           (<http://sourceforge.net/projects/afbackup>), and Bacula
           (<http://www.bacula.org>).  Amanda can also backup WinXX machines
           to tape using samba.  These packages can be used as back ends to
           BackupPC to backup the BackupPC server data to tape.

           Various programs and scripts use rsync to provide hardlinked
           backups.  See, for example, Mike Rubel’s site
           (<http://www.mikerubel.org/computers/rsync_snapshots>), JW
           Schultz’s dirvish (<http://www.dirvish.org>), Ben Escoto’s rdiff-
           backup (<http://rdiff-backup.stanford.edu>), and John Bowman’s
           rlbackup (<http://www.math.ualberta.ca/imaging/rlbackup>).

           BackupPC provides many additional features, such as compressed
           storage, hardlinking any matching files (rather than just files
           with the same name), and storing special files without root
           privileges.  But these other scripts provide simple and effective
           solutions and are worthy of consideration.

       Road map

       The new features planned for future releases of BackupPC are at
       <http://backuppc.sourceforge.net/faq/roadMap.html>.

       Comments and suggestions are welcome.

       You can help

       BackupPC is free. I work on BackupPC because I enjoy doing it and I
       like to contribute to the open source community.

       BackupPC already has more than enough features for my own needs.  The
       main compensation for continuing to work on BackupPC is knowing that
       more and more people find it useful.  So feedback is certainly
       appreciated, both positive and negative.

       Beyond being a satisfied user and telling other people about it,
       everyone is encouraged to add links to
       <http://backuppc.sourceforge.net> (I’ll see them via Google) or
       otherwise publicize BackupPC.  Unlike the commercial products in this
       space, I have a zero budget (in both time and money) for marketing, PR
       and advertising, so it’s up to all of you!  Feel free to vote for
       BackupPC at <http://freshmeat.net/projects/backuppc>.

       Also, everyone is encouraged to contribute patches, bug reports,
       feature and design suggestions, new code, FAQs, and documentation
       corrections or improvements.  Answering questions on the mail list is a
       big help too.

Installing BackupPC

       Requirements

       BackupPC requires:

       ·   A linux, solaris, or unix based server with a substantial amount of
           free disk space (see the next section for what that means). The CPU
           and disk performance on this server will determine how many
           simultaneous backups you can run. You should be able to run 4-8
           simultaneous backups on a moderately configured server.

           Several users have reported significantly better performance using
           reiser compared to ext3 for the BackupPC data file system.  It is
           also recommended you consider either an LVM or raid setup (either
           in HW or SW; eg: 3Ware RAID5) so that you can expand the file
           system as necessary.

           When BackupPC starts with an empty pool, all the backup data will
           be written to the pool on disk. After more backups are done, a
           higher percentage of incoming files will already be in the pool.
           BackupPC is able to avoid writing to disk new files that are
           already in the pool.  So over time disk writes will reduce
           significantly (by perhaps a factor of 20 or more), since eventually
           95% or more of incoming backup files are typically in the pool.
           Disk reads from the pool are still needed to do file compares to
           verify files are an exact match. So, with a mature pool, if a
           relatively fast client generates data at say 1MB/sec, and you run 4
           simultaneous backups, there will be an average server disk load of
           about 4MB/sec reads and 0.2MB/sec writes (assuming 95% of the
           incoming files are in the pool). These rates will be perhaps 40%
           lower if compression is on.

       ·   Perl version 5.6.0 or later. BackupPC has been tested with version
           5.6.x, and 5.8.x. If you don’t have perl, please see
           <http://www.cpan.org>.

       ·   Perl modules Compress::Zlib, Archive::Zip and File::RsyncP.  Try
           "perldoc Compress::Zlib" and "perldoc Archive::Zip" to see if you
           have these modules.  If not, fetch them from <http://www.cpan.org>
           and see the instructions below for how to build and install them.

           The File::RsyncP module is available from
           <http://perlrsync.sourceforge.net> or CPAN.  You’ll need to install
           the File::RsyncP module if you want to use Rsync as a transport
           method.

       ·   If you are using smb to backup WinXX machines you need smbclient
           and nmblookup from the samba package.  You will also need nmblookup
           if you are backing up linux/unix DHCP machines.  See
           <http://www.samba.org>.  Version 2.2.0 or later of Samba is
           required.  Samba versions 3.x are stable and now recommended
           instead of 2.x.

           See <http://www.samba.org> for source and binaries.  It’s pretty
           easy to fetch and compile samba, and just grab smbclient and
           nmblookup, without doing the installation. Alternatively,
           <http://www.samba.org> has binary distributions for most platforms.

       ·   If you are using tar to backup linux/unix machines you should have
           version 1.13.7 at a minimum, with version 1.13.20 or higher
           recommended.  Use "tar --version" to check your version.  Various
           GNU mirrors have the newest versions of tar, see for example
           <http://www.funet.fi/pub/gnu/alpha/gnu/tar>.  As of June 2003 the
           latest version is 1.13.25.

       ·   If you are using rsync to backup linux/unix machines you should
           have version 2.5.5 or higher on each client machine.  See
           <http://rsync.samba.org>. Use "rsync --version" to check your
           version.

           For BackupPC to use Rsync you will also need to install the perl
           File::RsyncP module, which is available from
           <http://perlrsync.sourceforge.net>.  Version 0.52 or later is
           required.

       ·   The Apache web server, see <http://www.apache.org>, preferably
           built with mod_perl support.

       How much disk space do I need?

       Here’s one real example for an environment that is backing up 65
       laptops with compression off. Each full backup averages 3.2GB. Each
       incremental backup averages about 0.2GB. Storing one full backup and
       two incremental backups per laptop is around 240GB of raw data. But
       because of the pooling of identical files, only 87GB is used.  This is
       without compression.

       Another example, with compression on: backing up 95 laptops, where each
       backup averages 3.6GB and each incremental averages about 0.3GB.
       Keeping three weekly full backups, and six incrementals is around
       1200GB of raw data.  Because of pooling and compression, only 150GB is
       needed.

       Here’s a rule of thumb. Add up the disk usage of all the machines you
       want to backup (210GB in the first example above). This is a rough
       minimum space estimate that should allow a couple of full backups and
       at least half a dozen incremental backups per machine. If compression
       is on you can reduce the storage requirements by maybe 30-40%.  Add
       some margin in case you add more machines or decide to keep more old
       backups.

       Your actual mileage will depend upon the types of clients, operating
       systems and applications you have. The more uniform the clients and
       applications the bigger the benefit from pooling common files.

       For example, the Eudora email tool stores each mail folder in a
       separate file, and attachments are extracted as separate files. So in
       the sadly common case of a large attachment emailed to many recipients,
       Eudora will extract the attachment into a new file. When these machines
       are backed up, only one copy of the file will be stored on the server,
       even though the file appears in many different full or incremental
       backups. In this sense Eudora is a "friendly" application from the
       point of view of backup storage requirements.

       An example at the other end of the spectrum is Outlook. Everything
       (email bodies, attachments, calendar, contact lists) is stored in a
       single file, which often becomes huge. Any change to this file requires
       a separate copy of the file to be saved during backup. Outlook is even
       more troublesome, since it keeps this file locked all the time, so it
       cannot be read by smbclient whenever Outlook is running.  See the
       Limitations section for more discussion of this problem.

       In addition to total disk space, you shold make sure you have plenty of
       inodes on your BackupPC data partition. Some users have reported
       running out of inodes on their BackupPC data partition.  So even if you
       have plenty of disk space, BackupPC will report failures when the
       inodes are exhausted.  This is a particular problem with ext2/ext3 file
       systems that have a fixed number of inodes when the file system is
       built.  Use "df -i" to see your inode usage.

       Step 1: Getting BackupPC

       Some linux distributions now include BackupPC.  The Debian
       distribution, supprted by Ludovic Drolez, can be found at
       <http://packages.debian.org/backuppc>; it should be included in the
       next stable Debian release.  On Debian, BackupPC can be installed with
       the command:

           apt-get install backuppc

       In the future there might be packages for Gentoo and other linux
       flavors.  If the packaged version is older than the released version
       then you will probably want to install the lastest version as described
       below.

       Otherwise, manually fetching and installing BackupPC is easy.  Start by
       downloading the latest version from <http://backuppc.sourceforge.net>.
       Hit the "Code" button, then select the "backuppc" or "backuppc-beta"
       package and download the latest version.

       Step 2: Installing the distribution

       First off, there are three perl modules you should install.  These are
       all optional, but highly recommended:

       Compress::Zlib
           To enable compression, you will need to install Compress::Zlib from
           <http://www.cpan.org>.  You can run "perldoc Compress::Zlib" to see
           if this module is installed.

       Archive::Zip
           To support restore via Zip archives you will need to install
           Archive::Zip, also from <http://www.cpan.org>.  You can run
           "perldoc Archive::Zip" to see if this module is installed.

       File::RsyncP
           To use rsync and rsyncd with BackupPC you will need to install
           File::RsyncP.  You can run "perldoc File::RsyncP" to see if this
           module is installed.  File::RsyncP is available from
           <http://perlrsync.sourceforge.net>.  Version 0.52 or later is
           required.

       To build and install these packages, fetch the tar.gz file and then run
       these commands:

           tar zxvf Archive-Zip-1.01.tar.gz
           cd Archive-Zip-1.01
           perl Makefile.PL
           make
           make test
           make install

       The same sequence of commands can be used for each module.

       Now let’s move onto BackupPC itself.  After fetching
       BackupPC-2.1.2.tar.gz, run these commands as root:

           tar zxf BackupPC-2.1.2.tar.gz
           cd BackupPC-2.1.2
           perl configure.pl

       In the future this release might also have patches available on the
       SourceForge site.  These patch files are text files, with a name of the
       form

           BackupPC-2.1.2plN.diff

       where N is the patch level, eg: pl5 is patch-level 5.  These patch
       files are cumulative: you only need apply the last patch file, not all
       the earlier patch files.  If a patch file is available, eg:
       BackupPC-2.1.2pl5.diff, you should apply the patch after extracting the
       tar file:

            # fetch BackupPC-2.1.2.tar.gz
            # fetch BackupPC-2.1.2pl5.diff
            tar zxf BackupPC-2.1.2.tar.gz
            cd BackupPC-2.1.2
            patch -p0 < ../BackupPC-2.1.2pl5.diff
            perl configure.pl

       A patch file includes comments that describe that bug fixes and
       changes.  Feel free to review it before you apply the patch.

       The configure.pl script also accepts command-line options if you wish
       to run it in a non-interactive manner.  It has self-contained
       documentation for all the command-line options, which you can read with
       perldoc:

           perldoc configure.pl

       When you run configure.pl you will be prompted for the full paths of
       various executables, and you will be prompted for the following
       information:

       BackupPC User
           It is best if BackupPC runs as a special user, eg backuppc, that
           has limited privileges. It is preferred that backuppc belongs to a
           system administrator group so that sys admin members can browse
           backuppc files, edit the configuration files and so on. Although
           configurable, the default settings leave group read permission on
           pool files, so make sure the BackupPC user’s group is chosen
           restrictively.

           On this installation, this is __BACKUPPCUSER__.

       Data Directory
           You need to decide where to put the data directory, below which all
           the BackupPC data is stored.  This needs to be a big file system.

           On this installation, this is __TOPDIR__.

       Install Directory
           You should decide where the BackupPC scripts, libraries and
           documentation should be installed, eg: /opt/local/BackupPC.

           On this installation, this is __INSTALLDIR__.

       CGI bin Directory
           You should decide where the BackupPC CGI script resides.  This will
           usually below Apache’s cgi-bin directory.

           On this installation, this is __CGIDIR__.

       Apache image directory
           A directory where BackupPC’s images are stored so that Apache can
           serve them.  This should be somewhere under Apache’s DocumentRoot
           directory.

       Step 3: Setting up config.pl

       After running configure.pl, browse through the config file,
       __TOPDIR__/conf/config.pl, and make sure all the default settings are
       correct. In particular, you will need to decide whether to use smb, tar
       or rsync transport (or whether to set it on a per-PC basis) and set the
       relevant parameters for that transport method.  See the section Client
       Setup for more details.

       Step 4: Setting up the hosts file

       The file __TOPDIR__/conf/hosts contains the list of clients to backup.
       BackupPC reads this file in three cases:

       ·   Upon startup.

       ·   When BackupPC is sent a HUP (-1) signal.  Assuming you installed
           the init.d script, you can also do this with "/etc/init.d/backuppc
           reload".

       ·   When the modification time of the hosts file changes.  BackupPC
           checks the modification time once during each regular wakeup.

       Whenever you change the hosts file (to add or remove a host) you can
       either do a kill -HUP BackupPC_pid or simply wait until the next
       regular wakeup period.

       Each line in the hosts file contains three fields, separated by white
       space:

       Host name
           This is typically the host name or NetBios name of the client
           machine and should be in lower case.  The host name can contain
           spaces (escape with a backslash), but it is not recommended.

           Please read the section How BackupPC Finds Hosts.

           In certain cases you might want several distinct clients to refer
           to the same physical machine.  For example, you might have a
           database you want to backup, and you want to bracket the backup of
           the database with shutdown/restart using $Conf{DumpPreUserCmd} and
           $Conf{DumpPostUserCmd}.  But you also want to backup the rest of
           the machine while the database is still running.  In the case you
           can specify two different clients in the host file, using any
           mnemonic name (eg: myhost_mysql and myhost), and use
           $Conf{ClientNameAlias} in myhost_mysql’s config.pl to specify the
           real host name of the machine.

       DHCP flag
           Starting with v2.0.0 the way hosts are discovered has changed and
           now in most cases you should specify 0 for the DHCP flag, even if
           the host has a dynamically assigned IP address.  Please read the
           section How BackupPC Finds Hosts to understand whether you need to
           set the DHCP flag.

           You only need to set DHCP to 1 if your client machine doesn’t
           respond to the NetBios multicast request:

               nmblookup myHost

           but does respond to a request directed to its IP address:

               nmblookup -A W.X.Y.Z

           If you do set DHCP to 1 on any client you will need to specify the
           range of DHCP addresses to search is specified in
           $Conf{DHCPAddressRanges}.

           Note also that the $Conf{ClientNameAlias} feature does not work for
           clients with DHCP set to 1.

       User name
           This should be the unix login/email name of the user who "owns" or
           uses this machine. This is the user who will be sent email about
           this machine, and this user will have permission to
           stop/start/browse/restore backups for this host.  Leave this blank
           if no specific person should receive email or be allowed to
           stop/start/browse/restore backups for this host.  Administrators
           will still have full permissions.

       More users
           Additional user names, separate by commas and with no white space,
           can be specified.  These users will also have full permission in
           the CGI interface to stop/start/browse/restore backups for this
           host.  These users will not be sent email about this host.

       The first non-comment line of the hosts file is special: it contains
       the names of the columns and should not be edited.

       Here’s a simple example of a hosts file:

           host        dhcp    user      moreUsers
           farside     0       craig     jim,dave
           larson      1       gary      andy

       Step 5: Client Setup

       Two methods for getting backup data from a client are supported: smb
       and tar. Smb or rsync are the preferred methods for WinXX clients and
       rsync or tar are the preferred methods for linux/unix clients.

       The transfer method is set using the $Conf{XferMethod} configuration
       setting. If you have a mixed environment (ie: you will use smb for some
       clients and tar for others), you will need to pick the most common
       choice for $Conf{XferMethod} for the main config.pl file, and then
       override it in the per-PC config file for those hosts that will use the
       other method.  (Or you could run two completely separate instances of
       BackupPC, with different data directories, one for WinXX and the other
       for linux/unix, but then common files between the different machine
       types will duplicated.)

       Here are some brief client setup notes:

       WinXX
           The preferred setup for WinXX clients is to set $Conf{XferMethod}
           to "smb".  (Actually, for v2.0.0, rsyncd is the better method for
           WinXX if you are prepared to run rsync/cygwin on your WinXX client.
           More information about this will be provided via the FAQ.)

           If you want to use rsyncd for WinXX clients you can find a pre-
           packaged zip file on <http://backuppc.sourceforge.net>. The package
           is called cygwin-rsync. It contains rsync.exe, template setup files
           and the minimal set of cygwin libraries for everything to run.  The
           README file contains instructions for running rsync as a service,
           so it starts automatically everytime you boot your machine.

           If you build your own rsync, for rsync 2.6.2 it is strongly
           recommended you apply the patch in the cygwin-rsync package on
           <http://backuppc.sourceforge.net>.  This patch adds the
           --checksum-seed option for checksum caching, and also sends all
           errors to the client, which is important so BackupPC can log all
           file access errors.

           Otherwise, to use SMB, you need to create shares for the data you
           want to backup. Open "My Computer", right click on the drive (eg:
           C), and select "Sharing..." (or select "Properties" and select the
           "Sharing" tab). In this dialog box you can enable sharing, select
           the share name and permissions.  Many machines will be configured
           by default to share the entire C drive as C$ using the
           administrator password.

           If this machine uses DHCP you will also need to make sure the
           NetBios name is set.  Go to Control Panel│System│Network
           Identification (on Win2K) or Control Panel│System│Computer Name (on
           WinXP).  Also, you should go to Control Panel│Network
           Connections│Local Area Connection│Properties│Internet Protocol
           (TCP/IP)│Properties│Advanced│WINS and verify that NetBios is not
           disabled.

           The relevant configuration settings are $Conf{SmbShareName},
           $Conf{SmbShareUserName}, $Conf{SmbSharePasswd},
           $Conf{SmbClientPath}, $Conf{SmbClientFullCmd},
           $Conf{SmbClientIncrCmd} and $Conf{SmbClientRestoreCmd}.

           BackupPC needs to know the smb share user name and password for a
           client machine that uses smb.  The user name is specified in
           $Conf{SmbShareUserName}. There are four ways to tell BackupPC the
           smb share password:

           *   As an environment variable BPC_SMB_PASSWD set before BackupPC
               starts.  If you start BackupPC manually the BPC_SMB_PASSWD
               variable must be set manually first.  For backward
               compatibility for v1.5.0 and prior, the environment variable
               PASSWD can be used if BPC_SMB_PASSWD is not set.  Warning: on
               some systems it is possible to see environment variables of
               running processes.

           *   Alternatively the BPC_SMB_PASSWD setting can be included in
               /etc/init.d/backuppc, in which case you must make sure this
               file is not world (other) readable.

           *   As a configuration variable $Conf{SmbSharePasswd} in
               __TOPDIR__/conf/config.pl.  If you put the password here you
               must make sure this file is not world (other) readable.

           *   As a configuration variable $Conf{SmbSharePasswd} in the per-PC
               configuration file, __TOPDIR__/pc/$host/config.pl. You will
               have to use this option if the smb share password is different
               for each host.  If you put the password here you must make sure
               this file is not world (other) readable.

           Placement and protection of the smb share password is a possible
           security risk, so please double-check the file and directory
           permissions.  In a future version there might be support for
           encryption of this password, but a private key will still have to
           be stored in a protected place.  Suggestions are welcome.

           As an alternative to setting $Conf{XferMethod} to "smb" (using
           smbclient) for WinXX clients, you can use an smb network filesystem
           (eg: ksmbfs or similar) on your linux/unix server to mount the
           share, and then set $Conf{XferMethod} to "tar" (use tar on the
           network mounted file system).

           Also, to make sure that file names with 8-bit characters are
           correctly transferred by smbclient you should add this to samba’s
           smb.conf file for samba 2.x:

               [global]
                   # Accept the windows charset
                   client code page = 850
                   character set = ISO8859-1

           For samba 3.x this should instead be:

               [global]
                   unix charset = ISO8859-1

           This setting should work for western europe.  See
           <http://www.oreilly.com/catalog/samba/chapter/book/ch08_03.html>
           for more information about settings for other languages.

       Linux/Unix
           The preferred setup for linux/unix clients is to set
           $Conf{XferMethod} to "rsync", "rsyncd" or "tar".

           You can use either rsync, smb, or tar for linux/unix machines. Smb
           requires that the Samba server (smbd) be run to provide the shares.
           Since the smb protocol can’t represent special files like symbolic
           links and fifos, tar and rsync are the better transport methods for
           linux/unix machines.  (In fact, by default samba makes symbolic
           links look like the file or directory that they point to, so you
           could get an infinite loop if a symbolic link points to the current
           or parent directory. If you really need to use Samba shares for
           linux/unix backups you should turn off the "follow symlinks" samba
           config setting. See the smb.conf manual page.)

           The requirements for each Xfer Method are:

           tar You must have GNU tar on the client machine.  Use "tar
               --version" or "gtar --version" to verify.  The version should
               be at least 1.13.7, and 1.13.20 or greater is recommended.  Tar
               is run on the client machine via rsh or ssh.

               The relevant configuration settings are $Conf{TarClientPath},
               $Conf{TarShareName}, $Conf{TarClientCmd}, $Conf{TarFullArgs},
               $Conf{TarIncrArgs}, and $Conf{TarClientRestoreCmd}.

           rsync
               You should have at least rsync 2.5.5, and the latest version
               2.5.6 is recommended.  Rsync is run on the remote client via
               rsh or ssh.

               The relevant configuration settings are $Conf{RsyncClientPath},
               $Conf{RsyncClientCmd}, $Conf{RsyncClientRestoreCmd},
               $Conf{RsyncShareName}, $Conf{RsyncArgs}, and
               $Conf{RsyncRestoreArgs}.

           rsyncd
               You should have at least rsync 2.5.5, and the latest version
               2.6.2 is recommended.  In this case the rsync daemon should be
               running on the client machine and BackupPC connects directly to
               it.

               The relevant configuration settings are
               $Conf{RsyncdClientPort}, $Conf{RsyncdUserName},
               $Conf{RsyncdPasswd}, $Conf{RsyncdAuthRequired},
               $Conf{RsyncShareName}, $Conf{RsyncArgs}, and
               $Conf{RsyncRestoreArgs}.  $Conf{RsyncShareName} is the name of
               an rsync module (ie: the thing in square brackets in rsyncd’s
               conf file -- see rsyncd.conf), not a file system path.

               Be aware that rsyncd will remove the leading ’/’ from path
               names in symbolic links if you specify "use chroot = no" in the
               rsynd.conf file.  See the rsyncd.conf manual page for more
               information.

           For linux/unix machines you should not backup "/proc".  This
           directory contains a variety of files that look like regular files
           but they are special files that don’t need to be backed up (eg:
           /proc/kcore is a regular file that contains physical memory).  See
           $Conf{BackupFilesExclude}.  It is safe to back up /dev since it
           contains mostly character-special and block-special files, which
           are correctly handed by BackupPC (eg: backing up /dev/hda5 just
           saves the block-special file information, not the contents of the
           disk).

           Alternatively, rather than backup all the file systems as a single
           share ("/"), it is easier to restore a single file system if you
           backup each file system separately.  To do this you should list
           each file system mount point in $Conf{TarShareName} or
           $Conf{RsyncShareName}, and add the --one-file-system option to
           $Conf{TarClientCmd} or add --one-file-system (note the different
           punctuation) to $Conf{RsyncArgs}.  In this case there is no need to
           exclude /proc explicitly since it looks like a different file
           system.

           Next you should decide whether to run tar over ssh, rsh or nfs. Ssh
           is the preferred method. Rsh is not secure and therefore not
           recommended.  Nfs will work, but you need to make sure that the
           BackupPC user (running on the server) has sufficient permissions to
           read all the files below the nfs mount.

           Ssh allows BackupPC to run as a privileged user on the client (eg:
           root), since it needs sufficient permissions to read all the backup
           files. Ssh is setup so that BackupPC on the server (an otherwise
           low privileged user) can ssh as root on the client, without being
           prompted for a password. There are two common versions of ssh: v1
           and v2. Here are some instructions for one way to setup ssh.
           (Check which version of SSH you have by typing "ssh" or "man ssh".)

       Mac OS X
           In general this should be similar to Linux/Unix machines.  Many
           users have reported success using xtar, which also backs up the Mac
           OS X resource forks.

           Other choices include rsync and Mark Stosberg reports that you can
           also use hfstar.  See
           <http://fink.sourceforge.net/pdb/package.php/hfstar>.

       SSH Setup
           SSH is a secure way to run tar or rsync on a backup client to
           extract the data.  SSH provides strong authentication and
           encryption of the network data.

           Note that if you run rsyncd (rsync daemon), ssh is not used.  In
           this case, rsyncd provides its own authentication, but there is no
           encryption of network data.  If you want encryption of network data
           you can use ssh to create a tunnel, or use a program like stunnel.
           If someone submits instructions I

           Setup instructions for ssh are at
           <http://backuppc.sourceforge.net/faq/ssh.html>.

       Clients that use DHCP
           If a client machine uses DHCP BackupPC needs some way to find the
           IP address given the host name.  One alternative is to set dhcp to
           1 in the hosts file, and BackupPC will search a pool of IP
           addresses looking for hosts.  More efficiently, it is better to set
           dhcp = 0 and provide a mechanism for BackupPC to find the IP
           address given the host name.

           For WinXX machines BackupPC uses the NetBios name server to
           determine the IP address given the host name.  For unix machines
           you can run nmbd (the NetBios name server) from the Samba
           distribution so that the machine responds to a NetBios name
           request. See the manual page and Samba documentation for more
           information.

           Alternatively, you can set $Conf{NmbLookupFindHostCmd} to any
           command that returns the IP address given the host name.

           Please read the section How BackupPC Finds Hosts for more details.

       Step 6: Running BackupPC

       The installation contains an init.d backuppc script that can be copied
       to /etc/init.d so that BackupPC can auto-start on boot.  See
       init.d/README for further instructions.

       BackupPC should be ready to start.  If you installed the init.d script,
       then you should be able to run BackupPC with:

           /etc/init.d/backuppc start

       (This script can also be invoked with "stop" to stop BackupPC and
       "reload" to tell BackupPC to reload config.pl and the hosts file.)

       Otherwise, just run

            __INSTALLDIR__/bin/BackupPC -d

       as user __BACKUPPCUSER__.  The -d option tells BackupPC to run as a
       daemon (ie: it does an additional fork).

       Any immediate errors will be printed to stderr and BackupPC will quit.
       Otherwise, look in __TOPDIR__/log/LOG and verify that BackupPC reports
       it has started and all is ok.

       Step 7: Talking to BackupPC

       Note: as of version 1.5.0, BackupPC no longer supports telnet to its
       TCP port.  First off, a unix domain socket is used instead of a TCP
       port.  (The TCP port can still be re-enabled if your installation has
       apache and BackupPC running on different machines.)  Secondly, even if
       you still use the TCP port, the messages exchanged over this interface
       are now protected by an MD5 digest based on a shared secret (see
       $Conf{ServerMesgSecret}) as well as sequence numbers and per-session
       unique keys, preventing forgery and replay attacks.

       You should verify that BackupPC is running by using
       BackupPC_serverMesg.  This sends a message to BackupPC via the unix (or
       TCP) socket and prints the response.

       You can request status information and start and stop backups using
       this interface. This socket interface is mainly provided for the CGI
       interface (and some of the BackupPC sub-programs use it too).  But
       right now we just want to make sure BackupPC is happy.  Each of these
       commands should produce some status output:

           __INSTALLDIR__/bin/BackupPC_serverMesg status info
           __INSTALLDIR__/bin/BackupPC_serverMesg status jobs
           __INSTALLDIR__/bin/BackupPC_serverMesg status hosts

       The output should be some hashes printed with Data::Dumper.  If it
       looks cryptic and confusing, and doesn’t look like an error message,
       then all is ok.

       The jobs status should initially show just BackupPC_trashClean.  The
       hosts status should produce a list of every host you have listed in
       __TOPDIR__/conf/hosts as part of a big cryptic output line.

       You can also request that all hosts be queued:

           __INSTALLDIR__/bin/BackupPC_serverMesg backup all

       At this point you should make sure the CGI interface works since it
       will be much easier to see what is going on.  That’s our next subject.

       Step 8: CGI interface

       The CGI interface script, BackupPC_Admin, is a powerful and flexible
       way to see and control what BackupPC is doing.  It is written for an
       Apache server.  If you don’t have Apache, see <http://www.apache.org>.

       There are two options for setting up the CGI interface: standard mode
       and using mod_perl.  Mod_perl provides much higher performance (around
       15x) and is the best choice if your Apache was built with mod_perl
       support.  To see if your apache was built with mod_perl run this
       command:

           httpd -l │ egrep mod_perl

       If this prints mod_perl.c then your Apache supports mod_perl.

       Using mod_perl with BackupPC_Admin requires a dedicated Apache to be
       run as the BackupPC user (__BACKUPPCUSER__).  This is because
       BackupPC_Admin needs permission to access various files in BackupPC’s
       data directories.  In contrast, the standard installation (without
       mod_perl) solves this problem by having BackupPC_Admin installed as
       setuid to the BackupPC user, so that BackupPC_Admin runs as the BackuPC
       user.

       Here are some specifics for each setup:

       Standard Setup
           The CGI interface should have been installed by the configure.pl
           script in __CGIDIR__/BackupPC_Admin.  BackupPC_Admin should have
           been installed as setuid to the BackupPC user (__BACKUPPCUSER__),
           in addition to user and group execute permission.

           You should be very careful about permissions on BackupPC_Admin and
           the directory __CGIDIR__: it is important that normal users cannot
           directly execute or change BackupPC_Admin, otherwise they can
           access backup files for any PC. You might need to change the group
           ownership of BackupPC_Admin to a group that Apache belongs to so
           that Apache can execute it (don’t add "other" execute permission!).
           The permissions should look like this:

               ls -l __CGIDIR__/BackupPC_Admin
               -swxr-x---    1 __BACKUPPCUSER__   web      82406 Jun 17 22:58 __CGIDIR__/BackupPC_Admin

           The setuid script won’t work unless perl on your machine was
           installed with setuid emulation.  This is likely the problem if you
           get an error saying such as "Wrong user: my userid is 25, instead
           of 150", meaning the script is running as the httpd user, not the
           BackupPC user.  This is because setuid scripts are disabled by the
           kernel in most flavors of unix and linux.

           To see if your perl has setuid emulation, see if there is a program
           called sperl5.6.0 (or sperl5.8.2 etc, based on your perl version)
           in the place where perl is installed. If you can’t find this
           program, then you have two options: rebuild and reinstall perl with
           the setuid emulation turned on (answer "y" to the question "Do you
           want to do setuid/setgid emulation?" when you run perl’s configure
           script), or switch to the mod_perl alternative for the CGI script
           (which doesn’t need setuid to work).

       Mod_perl Setup
           The advantage of the mod_perl setup is that no setuid script is
           needed, and there is a huge performance advantage.  Not only does
           all the perl code need to be parsed just once, the config.pl and
           hosts files, plus the connection to the BackupPC server are cached
           between requests.  The typical speedup is around 15 times.

           To use mod_perl you need to run Apache as user __BACKUPPCUSER__.
           If you need to run multiple Apache’s for different services then
           you need to create multiple top-level Apache directories, each with
           their own config file.  You can make copies of /etc/init.d/httpd
           and use the -d option to httpd to point each http to a different
           top-level directory.  Or you can use the -f option to explicitly
           point to the config file.  Multiple Apache’s will run on different
           Ports (eg: 80 is standard, 8080 is a typical alternative port
           accessed via http://yourhost.com:8080).

           Inside BackupPC’s Apache http.conf file you should check the
           settings for ServerRoot, DocumentRoot, User, Group, and Port.  See
           <http://httpd.apache.org/docs/server-wide.html> for more details.

           For mod_perl, BackupPC_Admin should not have setuid permission, so
           you should turn it off:

               chmod u-s __CGIDIR__/BackupPC_Admin

           To tell Apache to use mod_perl to execute BackupPC_Admin, add this
           to Apache’s 1.x httpd.conf file:

               <IfModule mod_perl.c>
                   PerlModule Apache::Registry
                   PerlTaintCheck On
                   <Location /cgi-bin/BackupPC/BackupPC_Admin>   # <--- change path as needed
                      SetHandler perl-script
                      PerlHandler Apache::Registry
                      Options ExecCGI
                      PerlSendHeader On
                   </Location>
               </IfModule>

           Apache 2.0.44 with Perl 5.8.0 on RedHat 7.1, Don Silvia reports
           that this works (with tweaks from Michael Tuzi):

               LoadModule perl_module modules/mod_perl.so
               PerlModule Apache2

               <Directory /path/to/cgi/>
                   SetHandler perl-script
                   PerlResponseHandler ModPerl::Registry
                   PerlOptions +ParseHeaders
                   Options +ExecCGI
                   Order deny,allow
                   Deny from all
                   Allow from 192.168.0
                   AuthName "Backup Admin"
                   AuthType Basic
                   AuthUserFile /path/to/user_file
                   Require valid-user
               </Directory>

           There are other optimizations and options with mod_perl.  For
           example, you can tell mod_perl to preload various perl modules,
           which saves memory compared to loading separate copies in every
           Apache process after they are forked.  See Stas’s definitive
           mod_perl guide at <http://perl.apache.org/guide>.

       BackupPC_Admin requires that users are authenticated by Apache.
       Specifically, it expects that Apache sets the REMOTE_USER environment
       variable when it runs.  There are several ways to do this.  One way is
       to create a .htaccess file in the cgi-bin directory that looks like:

           AuthGroupFile /etc/httpd/conf/group    # <--- change path as needed
           AuthUserFile /etc/http/conf/passwd     # <--- change path as needed
           AuthType basic
           AuthName "access"
           require valid-user

       You will also need "AllowOverride Indexes AuthConfig" in the Apache
       httpd.conf file to enable the .htaccess file. Alternatively, everything
       can go in the Apache httpd.conf file inside a Location directive. The
       list of users and password file above can be extracted from the NIS
       passwd file.

       One alternative is to use LDAP.  In Apache’s http.conf add these lines:

           LoadModule auth_ldap_module   modules/auth_ldap.so
           AddModule auth_ldap.c

           # cgi-bin - auth via LDAP (for BackupPC)
           <Location /cgi-binBackupPC/BackupPC_Admin>    # <--- change path as needed
             AuthType Basic
             AuthName "BackupPC login"
             # replace MYDOMAIN, PORT, ORG and CO as needed
             AuthLDAPURL ldap://ldap.MYDOMAIN.com:PORT/o=ORG,c=CO?uid?sub?(objectClass=*)
             require valid-user
           </Location>

       If you want to disable the user authentication you can set
       $Conf{CgiAdminUsers} to ’*’, which allows any user to have full access
       to all hosts and backups.  In this case the REMOTE_USER environment
       variable does not have to be set by Apache.

       Alternatively, you can force a particular user name by getting Apache
       to set REMOTE_USER, eg, to hardcode the user to www you could add this
       to Apache’s httpd.conf:

           <Location /cgi-bin/BackupPC/BackupPC_Admin>   # <--- change path as needed
               Setenv REMOTE_USER www
           </Location>

       Finally, you should also edit the config.pl file and adjust, as
       necessary, the CGI-specific settings.  They’re near the end of the
       config file. In particular, you should specify which users or groups
       have administrator (privileged) access: see the config settings
       $Conf{CgiAdminUserGroup} and $Conf{CgiAdminUsers}.  Also, the
       configure.pl script placed various images into $Conf{CgiImageDir} that
       BackupPC_Admin needs to serve up.  You should make sure that
       $Conf{CgiImageDirURL} is the correct URL for the image directory.

       See the section Fixing installation problems for suggestions on
       debugging the Apache authentication setup.

       How BackupPC Finds Hosts

       Starting with v2.0.0 the way hosts are discovered has changed.  In most
       cases you should specify 0 for the DHCP flag in the conf/hosts file,
       even if the host has a dynamically assigned IP address.

       BackupPC (starting with v2.0.0) looks up hosts with DHCP = 0 in this
       manner:

       ·   First DNS is used to lookup the IP address given the client’s name
           using perl’s gethostbyname() function.  This should succeed for
           machines that have fixed IP addresses that are known via DNS.  You
           can manually see whether a given host have a DNS entry according to
           perls’ gethostbyname function with this command:

               perl -e ’print(gethostbyname("myhost") ? "ok\n" : "not found\n");’

       ·   If gethostbyname() fails, BackupPC then attempts a NetBios
           multicast to find the host.  Provided your client machine is
           configured properly, it should respond to this NetBios multicast
           request.  Specifically, BackupPC runs a command of this form:

               nmblookup myhost

           If this fails you will see output like:

               querying myhost on 10.10.255.255
               name_query failed to find name myhost

           If this success you will see output like:

               querying myhost on 10.10.255.255
               10.10.1.73 myhost<00>

           Depending on your netmask you might need to specify the -B option
           to nmblookup.  For example:

               nmblookup -B 10.10.1.255 myhost

           If necessary, experiment on the nmblookup command that will return
           the IP address of the client given its name.  Then update
           $Conf{NmbLookupFindHostCmd} with any necessary options to
           nmblookup.

       For hosts that have the DHCP flag set to 1, these machines are
       discovered as follows:

       ·   A DHCP address pool ($Conf{DHCPAddressRanges}) needs to be
           specified.  BackupPC will check the NetBIOS name of each machine in
           the range using a command of the form:

               nmblookup -A W.X.Y.Z

           where W.X.Y.Z is each candidate address from
           $Conf{DHCPAddressRanges}.  Any host that has a valid NetBIOS name
           returned by this command (ie: matching an entry in the hosts file)
           will be backed up.  You can modify the specific nmblookup command
           if necessary via $Conf{NmbLookupCmd}.

       ·   You only need to use this DHCP feature if your client machine
           doesn’t respond to the NetBios multicast request:

               nmblookup myHost

           but does respond to a request directed to its IP address:

               nmblookup -A W.X.Y.Z

       Other installation topics

       Removing a client
           If there is a machine that no longer needs to be backed up (eg: a
           retired machine) you have two choices.  First, you can keep the
           backups accessible and browsable, but disable all new backups.
           Alternatively, you can completely remove the client and all its
           backups.

           To disable backups for a client there are two special values for
           $Conf{FullPeriod} in that client’s per-PC config.pl file:

           -1  Don’t do any regular backups on this machine.  Manually
               requested backups (via the CGI interface) will still occur.

           -2  Don’t do any backups on this machine.  Manually requested
               backups (via the CGI interface) will be ignored.

           This will still allow that client’s old backups to be browsable and
           restorable.

           To completely remove a client and all its backups, you should
           remove its entry in the conf/hosts file, and then delete the
           __TOPDIR__/pc/$host directory.  Whenever you change the hosts file,
           you should send BackupPC a HUP (-1) signal so that it re-reads the
           hosts file.  If you don’t do this, BackupPC will automatically re-
           read the hosts file at the next regular wakeup.

           Note that when you remove a client’s backups you won’t initially
           recover a lot of disk space.  That’s because the client’s files are
           still in the pool.  Overnight, when BackupPC_nightly next runs, all
           the unused pool files will be deleted and this will recover the
           disk space used by the client’s backups.

       Copying the pool
           If the pool disk requirements grow you might need to copy the
           entire data directory to a new (bigger) file system.  Hopefully you
           are lucky enough to avoid this by having the data directory on a
           RAID file system or LVM that allows the capacity to be grown in
           place by adding disks.

           The backup data directories contain large numbers of hardlinks.  If
           you try to copy the pool the target directory will occupy a lot
           more space if the hardlinks aren’t re-established.

           The GNU cp program with the -a option is aware of hardlinks and
           knows to re-establish them.  So GNU cp -a is the recommended way to
           copy the data directory and pool.  Don’t forget to stop BackupPC
           while the copy runs.

       Compressing an existing pool
           If you are upgrading BackupPC and want to turn compression on you
           have two choices:

           *   Simply turn on compression.  All new backups will be
               compressed. Both old (uncompressed) and new (compressed)
               backups can be browsed and viewed.  Eventually, the old backups
               will expire and all the pool data will be compressed. However,
               until the old backups expire, this approach could require 60%
               or more additional pool storage space to store both
               uncompressed and compressed versions of the backup files.

           *   Convert all the uncompressed pool files and backups to
               compressed.  The script
               __INSTALLDIR__/bin/BackupPC_compressPool does this.  BackupPC
               must not be running when you run BackupPC_compressPool.  Also,
               there must be no existing compressed backups when you run
               BackupPC_compressPool.

               BackupPC_compressPool compresses all the files in the
               uncompressed pool (__TOPDIR__/pool) and moves them to the
               compressed pool (__TOPDIR__/cpool). It rewrites the files in
               place, so that the existing hardlinks are not disturbed.

           The rest of this section discusses how to run
           BackupPC_compressPool.

           BackupPC_compressPool takes three command line options:

           -t  Test mode: do everything except actually replace the pool
               files.  Useful for estimating total run time without making any
               real changes.

           -r  Read check: re-read the compressed file and compare it against
               the original uncompressed file.  Can only be used in test mode.

           -c #
               Number of children to fork. BackupPC_compressPool can take a
               long time to run, so to speed things up it spawns four
               children, each working on a different part of the pool. You can
               change the number of children with the -c option.

           Here are the recommended steps for running BackupPC_compressPool:

           *   Stop BackupPC (eg: "/etc/init.d/backuppc stop").

           *   Set $Conf{CompressLevel} to a non-zero number (eg: 3).

           *   Do a dry run of BackupPC_compressPool.  Make sure you run this
               as the BackupPC user (__BACKUPPCUSER__):

                   BackupPC_compressPool -t -r

               The -t option (test mode) makes BackupPC_compressPool do all
               the steps, but not actually change anything. The -r option re-
               reads the compressed file and compares it against the original.

               BackupPC_compressPool gives a status as it completes each 1% of
               the job.  It also shows the cumulative compression ratio and
               estimated completion time.  Once you are comfortable that
               things look ok, you can kill BackupPC_compressPool or wait for
               it to finish.

           *   Now you are ready to run BackupPC_compressPool for real.  Once
               again, as the BackupPC user (__BACKUPPCUSER__), run:

                   BackupPC_compressPool

               You should put the output into a file and tail this file.  (The
               running time could be twice as long as the test mode since the
               test mode file writes are immediately followed by an unlink, so
               in test mode it is likely the file writes never make it to
               disk.)

               It is critical that BackupPC_compressPool runs to completion
               before re-starting BackupPC.  Before BackupPC_compressPool
               completes, none of the existing backups will be in a consistent
               state.  If you must stop BackupPC_compressPool for some reason,
               send it an INT or TERM signal and give it several seconds (or
               more) to clean up gracefully.  After that, you can re-run
               BackupPC_compressPool and it will start again where it left
               off.  Once again, it is critical that it runs to 100%
               completion.

           After BackupPC_compressPool completes you should have a complete
           set of compressed backups (and your disk usage should be lower).
           You can now re-start BackupPC.

       Fixing installation problems

       Please see the FAQ at <http://backuppc.sourceforge.net/faq> for
       debugging suggestions.

Restore functions

       BackupPC supports several different methods for restoring files. The
       most convenient restore options are provided via the CGI interface.
       Alternatively, backup files can be restored using manual commands.

       CGI restore options

       By selecting a host in the CGI interface, a list of all the backups for
       that machine will be displayed.  By selecting the backup number you can
       navigate the shares and directory tree for that backup.

       BackupPC’s CGI interface automatically fills incremental backups with
       the corresponding full backup, which means each backup has a filled
       appearance.  Therefore, there is no need to do multiple restores from
       the incremental and full backups: BackupPC does all the hard work for
       you.  You simply select the files and directories you want from the
       correct backup vintage in one step.

       You can download a single backup file at any time simply by selecting
       it.  Your browser should prompt you with the file name and ask you
       whether to open the file or save it to disk.

       Alternatively, you can select one or more files or directories in the
       currently selected directory and select "Restore selected files".  (If
       you need to restore selected files and directories from several
       different parent directories you will need to do that in multiple
       steps.)

       If you select all the files in a directory, BackupPC will replace the
       list of files with the parent directory.  You will be presented with a
       screen that has three options:

       Option 1: Direct Restore
           With this option the selected files and directories are restored
           directly back onto the host, by default in their original location.
           Any old files with the same name will be overwritten, so use
           caution.  You can optionally change the target host name, target
           share name, and target path prefix for the restore, allowing you to
           restore the files to a different location.

           Once you select "Start Restore" you will be prompted one last time
           with a summary of the exact source and target files and directories
           before you commit.  When you give the final go ahead the restore
           operation will be queued like a normal backup job, meaning that it
           will be deferred if there is a backup currently running for that
           host.  When the restore job is run, smbclient, tar, rsync or rsyncd
           is used (depending upon $Conf{XferMethod}) to actually restore the
           files.  Sorry, there is currently no option to cancel a restore
           that has been started.

           A record of the restore request, including the result and list of
           files and directories, is kept.  It can be browsed from the host’s
           home page.  $Conf{RestoreInfoKeepCnt} specifies how many old
           restore status files to keep.

           Note that for direct restore to work, the $Conf{XferMethod} must be
           able to write to the client.  For example, that means an SMB share
           for smbclient needs to be writable, and the rsyncd module needs
           "read only" set to "false".  This creates additional security
           risks.  If you only create read-only SMB shares (which is a good
           idea), then the direct restore will fail.  You can disable the
           direct restore option by setting $Conf{SmbClientRestoreCmd},
           $Conf{TarClientRestoreCmd} and $Conf{RsyncRestoreArgs} to undef.

       Option 2: Download Zip archive
           With this option a zip file containing the selected files and
           directories is downloaded.  The zip file can then be unpacked or
           individual files extracted as necessary on the host machine. The
           compression level can be specified.  A value of 0 turns off
           compression.

           When you select "Download Zip File" you should be prompted where to
           save the restore.zip file.

           BackupPC does not consider downloading a zip file as an actual
           restore operation, so the details are not saved for later browsing
           as in the first case.  However, a mention that a zip file was
           downloaded by a particular user, and a list of the files, does
           appear in BackupPC’s log file.

       Option 3: Download Tar archive
           This is identical to the previous option, except a tar file is
           downloaded rather than a zip file (and there is currently no
           compression option).

       Command-line restore options

       Apart from the CGI interface, BackupPC allows you to restore files and
       directories from the command line.  The following programs can be used:

       BackupPC_zcat
           For each file name argument it inflates (uncompresses) the file and
           writes it to stdout.  To use BackupPC_zcat you could give it the
           full file name, eg:

               __INSTALLDIR__/bin/BackupPC_zcat __TOPDIR__/pc/host/5/fc/fcraig/fexample.txt > example.txt

           It’s your responsibility to make sure the file is really
           compressed: BackupPC_zcat doesn’t check which backup the requested
           file is from.  BackupPC_zcat returns a non-zero status if it fails
           to uncompress a file.

       BackupPC_tarCreate
           BackupPC_tarCreate creates a tar file for any files or directories
           in a particular backup.  Merging of incrementals is done
           automatically, so you don’t need to worry about whether certain
           files appear in the incremental or full backup.

           The usage is:

              BackupPC_tarCreate [-t] [-h host] [-n dumpNum] [-s shareName]
                               [-r pathRemove] [-p pathAdd] [-b BLOCKS] [-w writeBufSz]
                               files/directories...

           The command-line files and directories are relative to the
           specified shareName.  The tar file is written to stdout.

           The required options are:

           -h host
               host from which the tar archive is created

           -n dumpNum
               dump number from which the tar archive is created

           -s shareName
               share name from which the tar archive is created

           Other options are:

           -t  print summary totals

           -r pathRemove
               path prefix that will be replaced with pathAdd

           -p pathAdd
               new path prefix

           -b BLOCKS
               the tar block size, default is 20, meaning tar writes data in
               20 * 512 bytes chunks.

           -w writeBufSz
               write buffer size, default 1048576 (1MB).  You can increase
               this if you are trying to stream to a fast tape device.

           The -h, -n and -s options specify which dump is used to generate
           the tar archive.  The -r and -p options can be used to relocate the
           paths in the tar archive so extracted files can be placed in a
           location different from their original location.

       BackupPC_zipCreate
           BackupPC_zipCreate creates a zip file for any files or directories
           in a particular backup.  Merging of incrementals is done
           automatically, so you don’t need to worry about whether certain
           files appear in the incremental or full backup.

           The usage is:

              BackupPC_zipCreate [-t] [-h host] [-n dumpNum] [-s shareName]
                               [-r pathRemove] [-p pathAdd] [-c compressionLevel]
                              files/directories...

           The command-line files and directories are relative to the
           specified shareName.  The zip file is written to stdout.

           The required options are:

           -h host
               host from which the zip archive is created

           -n dumpNum
               dump number from which the zip archive is created

           -s shareName
               share name from which the zip archive is created

           Other options are:

           -t  print summary totals

           -r pathRemove
               path prefix that will be replaced with pathAdd

           -p pathAdd
               new path prefix

           -c level
               compression level (default is 0, no compression)

           The -h, -n and -s options specify which dump is used to generate
           the zip archive.  The -r and -p options can be used to relocate the
           paths in the zip archive so extracted files can be placed in a
           location different from their original location.

       Each of these programs reside in __INSTALLDIR__/bin.

Archive functions

       BackupPC supports archiving to removable media. For users that require
       offsite backups, BackupPC can create archives that stream to tape
       devices, or create files of specified sizes to fit onto cd or dvd
       media.

       Each archive type is specified by a BackupPC host with its XferMethod
       set to ’archive’. This allows for multiple configurations at sites
       where there might be a combination of tape and cd/dvd backups being
       made.

       BackupPC provides a menu that allows one or more hosts to be archived.
       The most recent backup of each host is archived using
       BackupPC_tarCreate, and the output is optionally compressed and split
       into fixed-sized files (eg: 650MB).

       The archive for each host is done by default using
       __INSTALLDIR__/BackupPC_archiveHost.  This script can be copied and
       customized as needed.

       Configuring an Archive Host

       To create an Archive Host, add it to the hosts file just as any other
       host and call it a name that best describes the type of archive, e.g.
       ArchiveDLT

       To tell BackupPC that the Host is for Archives, create a config.pl file
       in the Archive Hosts’s pc directory, adding the following line:

       $Conf{XferMethod} = ’archive’;

       To further customise the archive’s parameters you can adding the
       changed parameters in the host’s config.pl file. The parameters are
       explained in the config.pl file.  Parameters may be fixed or the user
       can be allowed to change them (eg: output device).

       The per-host archive command is $Conf{ArchiveClientCmd}.  By default
       this invokes

            __INSTALLDIR__/BackupPC_archiveHost

       which you can copy and customize as necessary.

       Starting an Archive

       In the web interface, click on the Archive Host you wish to use. You
       will see a list of previous archives and a summary on each. By clicking
       the "Start Archive" button you are presented with the list of hosts and
       the approximate backup size (note this is raw size, not projected
       compressed size) Select the hosts you wish to archive and press the
       "Archive Selected Hosts" button.

       The next screen allows you to adjust the parameters for this archive
       run.  Press the "Start the Archive" to start archiving the selected
       hosts with the parameters displayed.

BackupPC Design

       Some design issues

       Pooling common files
           To quickly see if a file is already in the pool, an MD5 digest of
           the file length and contents is used as the file name in the pool.
           This can’t guarantee a file is identical: it just reduces the
           search to often a single file or handful of files. A complete file
           comparison is always done to verify if two files are really the
           same.

           Identical files on multiples backups are represented by hard links.
           Hardlinks are used so that identical files all refer to the same
           physical file on the server’s disk. Also, hard links maintain
           reference counts so that BackupPC knows when to delete unused files
           from the pool.

           For the computer-science majors among you, you can think of the
           pooling system used by BackupPC as just a chained hash table stored
           on a (big) file system.

       The hashing function
           There is a tradeoff between how much of file is used for the MD5
           digest and the time taken comparing all the files that have the
           same hash.

           Using the file length and just the first 4096 bytes of the file for
           the MD5 digest produces some repetitions.  One example: with
           900,000 unique files in the pool, this hash gives about 7,000
           repeated files, and in the worst case 500 files have the same hash.
           That’s not bad: we only have to do a single file compare 99.2% of
           the time.  But in the worst case we have to compare as many as 500
           files checking for a match.

           With a modest increase in CPU time, if we use the file length and
           the first 256K of the file we now only have 500 repeated files and
           in the worst case around 20 files have the same hash. Furthermore,
           if we instead use the first and last 128K of the file (more
           specifically, the first and eighth 128K chunks for files larger
           than 1MB) we get only 300 repeated files and in the worst case
           around 20 files have the same hash.

           Based on this experimentation, this is the hash function used by
           BackupPC.  It is important that you don’t change the hash function
           after files are already in the pool.  Otherwise your pool will grow
           to twice the size until all the old backups (and all the old files
           with old hashes) eventually expire.

       Compression
           BackupPC supports compression. It uses the deflate and inflate
           methods in the Compress::Zlib module, which is based on the zlib
           compression library (see <http://www.gzip.org/zlib/>).

           The $Conf{CompressLevel} setting specifies the compression level to
           use.  Zero (0) means no compression. Compression levels can be from
           1 (least cpu time, slightly worse compression) to 9 (most cpu time,
           slightly better compression). The recommended value is 3. Changing
           it to 5, for example, will take maybe 20% more cpu time and will
           get another 2-3% additional compression. Diminishing returns set in
           above 5.  See the zlib documentation for more information about
           compression levels.

           BackupPC implements compression with minimal CPU load. Rather than
           compressing every incoming backup file and then trying to match it
           against the pool, BackupPC computes the MD5 digest based on the
           uncompressed file, and matches against the candidate pool files by
           comparing each uncompressed pool file against the incoming backup
           file.  Since inflating a file takes roughly a factor of 10 less CPU
           time than deflating there is a big saving in CPU time.

           The combination of pooling common files and compression can yield a
           factor of 8 or more overall saving in backup storage.

       BackupPC operation

       BackupPC reads the configuration information from
       __TOPDIR__/conf/config.pl. It then runs and manages all the backup
       activity. It maintains queues of pending backup requests, user backup
       requests and administrative commands. Based on the configuration
       various requests will be executed simultaneously.

       As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
       to queue backups on all the PCs.  This is a four step process:

       1   For each host and DHCP address backup requests are queued on the
           background command queue.

       2   For each PC, BackupPC_dump is forked. Several of these may be run
           in parallel, based on the configuration. First a ping is done to
           see if the machine is alive. If this is a DHCP address, nmblookup
           is run to get the netbios name, which is used as the host name. If
           DNS lookup fails, $Conf{NmbLookupFindHostCmd} is run to find the IP
           address from the host name.  The file __TOPDIR__/pc/$host/backups
           is read to decide whether a full or incremental backup needs to be
           run. If no backup is scheduled, or the ping to $host fails, then
           BackupPC_dump exits.

           The backup is done using the specified XferMethod.  Either samba’s
           smbclient or tar over ssh/rsh/nfs piped into BackupPC_tarExtract,
           or rsync over ssh/rsh is run, or rsyncd is connected to, with the
           incoming data extracted to __TOPDIR__/pc/$host/new.  The XferMethod
           output is put into __TOPDIR__/pc/$host/XferLOG.

           The letter in the XferLOG file shows the type of object, similar to
           the first letter of the modes displayed by ls -l:

               d -> directory
               l -> symbolic link
               b -> block special file
               c -> character special file
               p -> pipe file (fifo)
               nothing -> regular file

           The words mean:

           create
               new for this backup (ie: directory or file not in pool)

           pool
               found a match in the pool

           same
               file is identical to previous backup (contents were checksummed
               and verified during full dump).

           skip
               file skipped in incremental because attributes are the same
               (only displayed if $Conf{XferLogLevel} >= 2).

           As BackupPC_tarExtract extracts the files from smbclient or tar, or
           as rsync runs, it checks each file in the backup to see if it is
           identical to an existing file from any previous backup of any PC.
           It does this without needed to write the file to disk. If the file
           matches an existing file, a hardlink is created to the existing
           file in the pool.  If the file does not match any existing files,
           the file is written to disk and the file name is saved in
           __TOPDIR__/pc/$host/NewFileList for later processing by
           BackupPC_link.  BackupPC_tarExtract and rsync can handle
           arbitrarily large files and multiple candidate matching files
           without needing to write the file to disk in the case of a match.
           This significantly reduces disk writes (and also reads, since the
           pool file comparison is done disk to memory, rather than disk to
           disk).

           Based on the configuration settings, BackupPC_dump checks each old
           backup to see if any should be removed.  Any expired backups are
           moved to __TOPDIR__/trash for later removal by BackupPC_trashClean.

       3   For each complete, good, backup, BackupPC_link is run.  To avoid
           race conditions as new files are linked into the pool area, only a
           single BackupPC_link program runs at a time and the rest are
           queued.

           BackupPC_link reads the NewFileList written by BackupPC_dump and
           inspects each new file in the backup. It re-checks if there is a
           matching file in the pool (another BackupPC_link could have added
           the file since BackupPC_dump checked). If so, the file is removed
           and replaced by a hard link to the existing file. If the file is
           new, a hard link to the file is made in the pool area, so that this
           file is available for checking against each new file and new
           backup.

           Then, if $Conf{IncrFill} is set (note that the default setting is
           off), for each incremental backup, hard links are made in the new
           backup to all files that were not extracted during the incremental
           backups.  The means the incremental backup looks like a complete
           image of the PC (with the exception that files that were removed on
           the PC since the last full backup will still appear in the backup
           directory tree).

           The CGI interface knows how to merge unfilled incremental backups
           will the most recent prior filled (full) backup, giving the
           incremental backups a filled appearance.  The default for
           $Conf{IncrFill} is off, since there is no need to fill incremental
           backups.  This saves some level of disk activity, since lots of
           extra hardlinks are no longer needed (and don’t have to be deleted
           when the backup expires).

       4   BackupPC_trashClean is always run in the background to remove any
           expired backups. Every 5 minutes it wakes up and removes all the
           files in __TOPDIR__/trash.

           Also, once each night, BackupPC_nightly is run to complete some
           additional administrative tasks, such as cleaning the pool.  This
           involves removing any files in the pool that only have a single
           hard link (meaning no backups are using that file).  Again, to
           avoid race conditions, BackupPC_nightly is only run when there are
           no BackupPC_dump or BackupPC_link processes running.  Therefore,
           when it is time to run BackupPC_nightly, no new backups are started
           and BackupPC waits until all backups have finished.  Then
           BackupPC_nightly is run, and until it finishes no new backups are
           started.  If BackupPC_nightly takes too long to run, the settings
           $Conf{MaxBackupPCNightlyJobs} and $Conf{BackupPCNightlyPeriod} can
           be used to run several BackupPC_nightly processes in parallel, and
           to split its job over several nights.

       BackupPC also listens for TCP connections on $Conf{ServerPort}, which
       is used by the CGI script BackupPC_Admin for status reporting and user-
       initiated backup or backup cancel requests.

       Storage layout

       BackupPC resides in three directories:

       __INSTALLDIR__
           Perl scripts comprising BackupPC reside in __INSTALLDIR__/bin,
           libraries are in __INSTALLDIR__/lib and documentation is in
           __INSTALLDIR__/doc.

       __CGIDIR__
           The CGI script BackupPC_Admin resides in this cgi binary directory.

       __TOPDIR__
           All of BackupPC’s data (PC backup images, logs, configuration
           information) is stored below this directory.

       Below __TOPDIR__ are several directories:

       __TOPDIR__/conf
           The directory __TOPDIR__/conf contains:

           config.pl
               Configuration file. See Configuration file below for more
               details.

           hosts
               Hosts file, which lists all the PCs to backup.

       __TOPDIR__/log
           The directory __TOPDIR__/log contains:

           LOG Current (today’s) log file output from BackupPC.

           LOG.0 or LOG.0.z
               Yesterday’s log file output.  Log files are aged daily and
               compressed (if compression is enabled), and old LOG files are
               deleted.

           BackupPC.pid
               Contains BackupPC’s process id.

           status.pl
               A summary of BackupPC’s status written periodically by BackupPC
               so that certain state information can be maintained if BackupPC
               is restarted.  Should not be edited.

           UserEmailInfo.pl
               A summary of what email was last sent to each user, and when
               the last email was sent.  Should not be edited.

       __TOPDIR__/trash
           Any directories and files below this directory are periodically
           deleted whenever BackupPC_trashClean checks. When a backup is
           aborted or when an old backup expires, BackupPC_dump simply moves
           the directory to __TOPDIR__/trash for later removal by
           BackupPC_trashClean.

       __TOPDIR__/pool
           All uncompressed files from PC backups are stored below
           __TOPDIR__/pool.  Each file’s name is based on the MD5 hex digest
           of the file contents.  Specifically, for files less than 256K, the
           file length and the entire file is used. For files up to 1MB, the
           file length and the first and last 128K are used. Finally, for
           files longer than 1MB, the file length, and the first and eighth
           128K chunks for the file are used.

           Each file is stored in a subdirectory X/Y/Z, where X, Y, Z are the
           first 3 hex digits of the MD5 digest.

           For example, if a file has an MD5 digest of 123456789abcdef0, the
           file is stored in __TOPDIR__/pool/1/2/3/123456789abcdef0.

           The MD5 digest might not be unique (especially since not all the
           file’s contents are used for files bigger than 256K). Different
           files that have the same MD5 digest are stored with a trailing
           suffix "_n" where n is an incrementing number starting at 0. So,
           for example, if two additional files were identical to the first,
           except the last byte was different, and assuming the file was
           larger than 1MB (so the MD5 digests are the same but the files are
           actually different), the three files would be stored as:

                   __TOPDIR__/pool/1/2/3/123456789abcdef0
                   __TOPDIR__/pool/1/2/3/123456789abcdef0_0
                   __TOPDIR__/pool/1/2/3/123456789abcdef0_1

           Both BackupPC_dump (actually, BackupPC_tarExtract) and
           BackupPC_link are responsible for checking newly backed up files
           against the pool. For each file, the MD5 digest is used to generate
           a file name in the pool directory. If the file exists in the pool,
           the contents are compared.  If there is no match, additional files
           ending in "_n" are checked.  (Actually, BackupPC_tarExtract
           compares multiple candidate files in parallel.)  If the file
           contents exactly match, the file is created by simply making a hard
           link to the pool file (this is done by BackupPC_tarExtract as the
           backup proceeds). Otherwise, BackupPC_tarExtract writes the new
           file to disk and a new hard link is made in the pool to the file
           (this is done later by BackupPC_link).

           Therefore, every file in the pool will have at least 2 hard links
           (one for the pool file and one for the backup file below
           __TOPDIR__/pc).  Identical files from different backups or PCs will
           all be linked to the same file.  When old backups are deleted, some
           files in the pool might only have one link.  BackupPC_nightly
           checks the entire pool and removes all files that have only a
           single link, thereby recovering the storage for that file.

           One other issue: zero length files are not pooled, since there are
           a lot of these files and on most file systems it doesn’t save any
           disk space to turn these files into hard links.

       __TOPDIR__/cpool
           All compressed files from PC backups are stored below
           __TOPDIR__/cpool.  Its layout is the same as __TOPDIR__/pool, and
           the hashing function is the same (and, importantly, based on the
           uncompressed file, not the compressed file).

       __TOPDIR__/pc/$host
           For each PC $host, all the backups for that PC are stored below the
           directory __TOPDIR__/pc/$host.  This directory contains the
           following files:

           LOG Current log file for this PC from BackupPC_dump.

           LOG.0 or LOG.0.z
               Last month’s log file.  Log files are aged monthly and
               compressed (if compression is enabled), and old LOG files are
               deleted.

           XferERR or XferERR.z
               Output from the transport program (ie: smbclient, tar or rsync)
               for the most recent failed backup.

           new Subdirectory in which the current backup is stored.  This
               directory is renamed if the backup succeeds.

           XferLOG or XferLOG.z
               Output from the transport program (ie: smbclient, tar or rsync)
               for the current backup.

           nnn (an integer)
               Successful backups are in directories numbered sequentially
               starting at 0.

           XferLOG.nnn or XferLOG.nnn.z
               Output from the transport program (ie: smbclient, tar or rsync)
               corresponding to backup number nnn.

           RestoreInfo.nnn
               Information about restore request #nnn including who, what,
               when, and why. This file is in Data::Dumper format.  (Note that
               the restore numbers are not related to the backup number.)

           RestoreLOG.nnn.z
               Output from smbclient, tar or rsync during restore #nnn.  (Note
               that the restore numbers are not related to the backup number.)

           ArchiveInfo.nnn
               Information about archive request #nnn including who, what,
               when, and why. This file is in Data::Dumper format.  (Note that
               the archive numbers are not related to the restore or backup
               number.)

           ArchiveLOG.nnn.z
               Output from archive #nnn.  (Note that the archive numbers are
               not related to the backup or restore number.)

           config.pl
               Optional configuration settings specific to this host.
               Settings in this file override the main configuration file.

           backups
               A tab-delimited ascii table listing information about each
               successful backup, one per row.  The columns are:

               num The backup number, an integer that starts at 0 and
                   increments for each successive backup.  The corresponding
                   backup is stored in the directory num (eg: if this field is
                   5, then the backup is stored in __TOPDIR__/pc/$host/5).

               type
                   Set to "full" or "incr" for full or incremental backup.

               startTime
                   Start time of the backup in unix seconds.

               endTime
                   Stop time of the backup in unix seconds.

               nFiles
                   Number of files backed up (as reported by smbclient, tar or
                   rsync).

               size
                   Total file size backed up (as reported by smbclient, tar or
                   rsync).

               nFilesExist
                   Number of files that were already in the pool (as
                   determined by BackupPC_dump and BackupPC_link).

               sizeExist
                   Total size of files that were already in the pool (as
                   determined by BackupPC_dump and BackupPC_link).

               nFilesNew
                   Number of files that were not in the pool (as determined by
                   BackupPC_link).

               sizeNew
                   Total size of files that were not in the pool (as
                   determined by BackupPC_link).

               xferErrs
                   Number of errors or warnings from smbclient, tar or rsync.

               xferBadFile
                   Number of errors from smbclient that were bad file errors
                   (zero otherwise).

               xferBadShare
                   Number of errors from smbclient that were bad share errors
                   (zero otherwise).

               tarErrs
                   Number of errors from BackupPC_tarExtract.

               compress
                   The compression level used on this backup.  Zero or empty
                   means no compression.

               sizeExistComp
                   Total compressed size of files that were already in the
                   pool (as determined by BackupPC_dump and BackupPC_link).

               sizeNewComp
                   Total compressed size of files that were not in the pool
                   (as determined by BackupPC_link).

               noFill
                   Set if this backup has not been filled in with the most
                   recent previous filled or full backup.  See
                   $Conf{IncrFill}.

               fillFromNum
                   If this backup was filled (ie: noFill is 0) then this is
                   the number of the backup that it was filled from

               mangle
                   Set if this backup has mangled file names and attributes.
                   Always true for backups in v1.4.0 and above.  False for all
                   backups prior to v1.4.0.

               xferMethod
                   Set to the value of $Conf{XferMethod} when this dump was
                   done.

               level
                   The level of this dump.  A full dump is level 0.  Currently
                   incrementals are 1.  But when multi-level incrementals are
                   supported this will reflect each dump’s incremental level.

           restores
               A tab-delimited ascii table listing information about each
               requested restore, one per row.  The columns are:

               num Restore number (matches the suffix of the RestoreInfo.nnn
                   and RestoreLOG.nnn.z file), unrelated to the backup number.

               startTime
                   Start time of the restore in unix seconds.

               endTime
                   End time of the restore in unix seconds.

               result
                   Result (ok or failed).

               errorMsg
                   Error message if restore failed.

               nFiles
                   Number of files restored.

               size
                   Size in bytes of the restored files.

               tarCreateErrs
                   Number of errors from BackupPC_tarCreate during restore.

               xferErrs
                   Number of errors from smbclient, tar or rsync during
                   restore.

           archives
               A tab-delimited ascii table listing information about each
               requested archive, one per row.  The columns are:

               num Archive number (matches the suffix of the ArchiveInfo.nnn
                   and ArchiveLOG.nnn.z file), unrelated to the backup or
                   restore number.

               startTime
                   Start time of the restore in unix seconds.

               endTime
                   End time of the restore in unix seconds.

               result
                   Result (ok or failed).

               errorMsg
                   Error message if archive failed.

       Compressed file format

       The compressed file format is as generated by Compress::Zlib::deflate
       with one minor, but important, tweak. Since Compress::Zlib::inflate
       fully inflates its argument in memory, it could take large amounts of
       memory if it was inflating a highly compressed file. For example, a
       200MB file of 0x0 bytes compresses to around 200K bytes. If
       Compress::Zlib::inflate was called with this single 200K buffer, it
       would need to allocate 200MB of memory to return the result.

       BackupPC watches how efficiently a file is compressing. If a big file
       has very high compression (meaning it will use too much memory when it
       is inflated), BackupPC calls the flush() method, which gracefully
       completes the current compression.  BackupPC then starts another
       deflate and simply appends the output file.  So the BackupPC compressed
       file format is one or more concatenated deflations/flushes.  The
       specific ratios that BackupPC uses is that if a 6MB chunk compresses to
       less than 64K then a flush will be done.

       Back to the example of the 200MB file of 0x0 bytes.  Adding flushes
       every 6MB adds only 200 or so bytes to the 200K output.  So the storage
       cost of flushing is negligible.

       To easily decompress a BackupPC compressed file, the script
       BackupPC_zcat can be found in __INSTALLDIR__/bin.  For each file name
       argument it inflates the file and writes it to stdout.

       Rsync checksum caching

       An incremental backup with rsync compares attributes on the client with
       the last full backup.  Any files with identical attributes are skipped.
       A full backup with rsync sets the --ignore-times option, which causes
       every file to be examined independent of attributes.

       Each file is examined by generating block checksums (default 2K blocks)
       on the receiving side (that’s the BackupPC side), sending those
       checksums to the client, where the remote rsync matches those checksums
       with the corresponding file.  The matching blocks and new data is sent
       back, allowing the client file to be reassembled.  A checksum for the
       entire file is sent to as an extra check the the reconstructed file is
       correct.

       This results in significant disk IO and computation for BackupPC: every
       file in a full backup, or any file with non-matching attributes in an
       incremental backup, needs to be uncompressed, block checksums computed
       and sent.  Then the receiving side reassembles the file and has to
       verify the whole-file checksum.  Even if the file is identical, prior
       to 2.1.0, BackupPC had to read and uncompress the file twice, once to
       compute the block checksums and later to verify the whole-file
       checksum.

       Starting in 2.1.0, BackupPC supports optional checksum caching, which
       means the block and file checksums only need to be computed once for
       each file.  This results in a significant performance improvement.
       This only works for compressed pool files.  It is enabled by adding

               ’--checksum-seed=32761’,

       to $Conf{RsyncArgs} and $Conf{RsyncRestoreArgs}.

       Rsync versions prior to and including rsync-2.6.2 need a small patch to
       add support for the --checksum-seed option.  This patch is available in
       the cygwin-rsyncd package at <http://backuppc.sourceforge.net>.  This
       patch is already included in rsync CVS, so it will be standard in
       future versions of rsync.

       When this option is present, BackupPC will add block and file checksums
       to the compressed pool file the next time a pool file is used and it
       doesn’t already have cached checksums.  The first time a new file is
       written to the pool, the checksums are not appended.  The next time
       checksums are needed for a file, they are computed and added.  So the
       full performance benefit of checksum caching won’t be noticed until the
       third time a pool file is used (eg: the third full backup).

       With checksum caching enabled, there is a risk that should a file’s
       contents in the pool be corrupted due to a disk problem, but the cached
       checksums are still correct, the corruption will not be detected by a
       full backup, since the file contents are no longer read and compared.
       To reduce the chance that this remains undetected, BackupPC can recheck
       cached checksums for a fraction of the files.  This fraction is set
       with the $Conf{RsyncCsumCacheVerifyProb} setting.  The default value of
       0.01 means that 1% of the time a file’s checksums are read, the
       checksums are verified.  This reduces performance slightly, but, over
       time, ensures that files contents are in sync with the cached
       checksums.

       The format of the cached checksum data can be discovered by looking at
       the code.  Basically, the first byte of the compressed file is changed
       to denote that checksums are appended.  The block and file checksum
       data, plus some other information and magic word, are appended to the
       compressed file.  This allows the cache update to be done in-place.

       File name mangling

       Backup file names are stored in "mangled" form. Each node of a path is
       preceded by "f" (mnemonic: file), and special characters (\n, \r, % and
       /) are URI-encoded as "%xx", where xx is the ascii character’s hex
       value.  So c:/craig/example.txt is now stored as
       fc/fcraig/fexample.txt.

       This was done mainly so meta-data could be stored alongside the backup
       files without name collisions. In particular, the attributes for the
       files in a directory are stored in a file called "attrib", and mangling
       avoids file name collisions (I discarded the idea of having a duplicate
       directory tree for every backup just to store the attributes). Other
       meta-data (eg: rsync checksums) could be stored in file names preceded
       by, eg, "c". There are two other benefits to mangling: the share name
       might contain "/" (eg: "/home/craig" for tar transport), and I wanted
       that represented as a single level in the storage tree. Secondly, as
       files are written to NewFileList for later processing by BackupPC_link,
       embedded newlines in the file’s path will cause problems which are
       avoided by mangling.

       The CGI script undoes the mangling, so it is invisible to the user.
       Old (unmangled) backups are still supported by the CGI interface.

       Special files

       Linux/unix file systems support several special file types: symbolic
       links, character and block device files, fifos (pipes) and unix-domain
       sockets. All except unix-domain sockets are supported by BackupPC
       (there’s no point in backing up or restoring unix-domain sockets since
       they only have meaning after a process creates them). Symbolic links
       are stored as a plain file whose contents are the contents of the link
       (not the file it points to). This file is compressed and pooled like
       any normal file. Character and block device files are also stored as
       plain files, whose contents are two integers separated by a comma; the
       numbers are the major and minor device number. These files are
       compressed and pooled like any normal file. Fifo files are stored as
       empty plain files (which are not pooled since they have zero size). In
       all cases, the original file type is stored in the attrib file so it
       can be correctly restored.

       Hardlinks are also supported.  When GNU tar first encounters a file
       with more than one link (ie: hardlinks) it dumps it as a regular file.
       When it sees the second and subsequent hardlinks to the same file, it
       dumps just the hardlink information.  BackupPC correctly recognizes
       these hardlinks and stores them just like symlinks: a regular text file
       whose contents is the path of the file linked to.  The CGI script will
       download the original file when you click on a hardlink.

       Also, BackupPC_tarCreate has enough magic to re-create the hardlinks
       dynamically based on whether or not the original file and hardlinks are
       both included in the tar file.  For example, imagine a/b/x is a
       hardlink to a/c/y.  If you use BackupPC_tarCreate to restore directory
       a, then the tar file will include a/b/x as the original file and a/c/y
       will be a hardlink to a/b/x.  If, instead you restore a/c, then the tar
       file will include a/c/y as the original file, not a hardlink.

       Attribute file format

       The unix attributes for the contents of a directory (all the files and
       directories in that directory) are stored in a file called attrib.
       There is a single attrib file for each directory in a backup.  For
       example, if c:/craig contains a single file c:/craig/example.txt, that
       file would be stored as fc/fcraig/fexample.txt and there would be an
       attribute file in fc/fcraig/attrib (and also fc/attrib and ./attrib).
       The file fc/fcraig/attrib would contain a single entry containing the
       attributes for fc/fcraig/fexample.txt.

       The attrib file starts with a magic number, followed by the
       concatenation of the following information for each file:

       ·   File name length in perl’s pack "w" format (variable length base
           128).

       ·   File name.

       ·   The unix file type, mode, uid, gid and file size divided by 4GB and
           file size modulo 4GB (type mode uid gid sizeDiv4GB sizeMod4GB), in
           perl’s pack "w" format (variable length base 128).

       ·   The unix mtime (unix seconds) in perl’s pack "N" format (32 bit
           integer).

       The attrib file is also compressed if compression is enabled.  See the
       lib/BackupPC/Attrib.pm module for full details.

       Attribute files are pooled just like normal backup files.  This saves
       space if all the files in a directory have the same attributes across
       multiple backups, which is common.

       Optimizations

       BackupPC doesn’t care about the access time of files in the pool since
       it saves attribute meta-data separate from the files.  Since BackupPC
       mostly does reads from disk, maintaining the access time of files
       generates a lot of unnecessary disk writes.  So, provided BackupPC has
       a dedicated data disk, you should consider mounting BackupPC’s data
       directory with the noatime attribute (see mount(1)).

       Limitations

       BackupPC isn’t perfect (but it is getting better). Please see
       <http://backuppc.sourceforge.net/faq/limitations.html> for a discussion
       of some of BackupPC’s limitations.

       Security issues

       Please see <http://backuppc.sourceforge.net/faq/security.html> for a
       discussion of some of various security issues.

Configuration File

       The BackupPC configuration file resides in __TOPDIR__/conf/config.pl.
       Optional per-PC configuration files reside in
       __TOPDIR__/pc/$host/config.pl.  This file can be used to override
       settings just for a particular PC.

       Modifying the main configuration file

       The configuration file is a perl script that is executed by BackupPC,
       so you should be careful to preserve the file syntax (punctuation,
       quotes etc) when you edit it. It is recommended that you use CVS, RCS
       or some other method of source control for changing config.pl.

       BackupPC reads or re-reads the main configuration file and the hosts
       file in three cases:

       ·   Upon startup.

       ·   When BackupPC is sent a HUP (-1) signal.  Assuming you installed
           the init.d script, you can also do this with "/etc/init.d/backuppc
           reload".

       ·   When the modification time of config.pl file changes.  BackupPC
           checks the modification time once during each regular wakeup.

       Whenever you change the configuration file you can either do a kill
       -HUP BackupPC_pid or simply wait until the next regular wakeup period.

       Each time the configuration file is re-read a message is reported in
       the LOG file, so you can tail it (or view it via the CGI interface) to
       make sure your kill -HUP worked. Errors in parsing the configuration
       file are also reported in the LOG file.

       The optional per-PC configuration file (__TOPDIR__/pc/$host/config.pl)
       is read whenever it is needed by BackupPC_dump, BackupPC_link and
       others.

       Configuration file includes

       If you have a heterogeneous set of clients (eg: a variety of WinXX and
       linux/unix machines) you will need to create host-specific config.pl
       files for some or all of these machines to customize the default
       settings from the master config.pl file (at a minimum to set
       $Conf{XferMethod}).

       Since the config.pl file is just regular perl code, you can include one
       config file from another.  For example, imagine you had three general
       classes of machines: WinXX desktops, linux machines in the DMZ and
       linux desktops.  You could create three config files in
       __TOPDIR__/conf:

           __TOPDIR__/conf/ConfigWinDesktop.pl
           __TOPDIR__/conf/ConfigLinuxDMZ.pl
           __TOPDIR__/conf/ConfigLinuxDesktop.pl

       From each client’s directory you can either add a symbolic link to the
       appropriate config file:

           cd __TOPDIR__/pc/$host
           ln -s ../../conf/ConfigWinDesktop.pl config.pl

       or, better yet, create a config.pl file in __TOPDIR__/pc/$host that
       includes the default config.pl file using perl’s "do" command:

           do "__TOPDIR__/conf/ConfigWinDesktop.pl";

       This alternative allows you to set other configuration options specific
       to each host after the "do" command (perhaps even overriding the
       settings in the included file).

       Note that you could also include snippets of configuration settings
       from the main configuration file.  However, be aware that the
       modification-time checking that BackupPC does only applies to the main
       configuration file: if you change one of the included files, BackupPC
       won’t notice.  You will need to either touch the main configuration
       file too, or send BackupPC a HUP (-1) signal.

Configuration Parameters

       The configuration parameters are divided into five general groups.  The
       first group (general server configuration) provides general
       configuration for BackupPC.  The next two groups describe what to
       backup, when to do it, and how long to keep it.  The fourth group are
       settings for email reminders, and the final group contains settings for
       the CGI interface.

       All configuration settings in the second through fifth groups can be
       overridden by the per-PC config.pl file.

       General server configuration

       $Conf{ServerHost} = ’’;
           Host name on which the BackupPC server is running.

       $Conf{ServerPort} = -1;
           TCP port number on which the BackupPC server listens for and
           accepts connections.  Normally this should be disabled (set to -1).
           The TCP port is only needed if apache runs on a different machine
           from BackupPC.  In that case, set this to any spare port number
           over 1024 (eg: 2359).  If you enable the TCP port, make sure you
           set $Conf{ServerMesgSecret} too!

       $Conf{ServerMesgSecret} = ’’;
           Shared secret to make the TCP port secure.  Set this to a hard to
           guess string if you enable the TCP port (ie: $Conf{ServerPort} >
           0).

           To avoid possible attacks via the TCP socket interface, every
           client message is protected by an MD5 digest. The MD5 digest
           includes four items:
             - a seed that is sent to the client when the connection opens
             - a sequence number that increments for each message
             - a shared secret that is stored in $Conf{ServerMesgSecret}
             - the message itself.

           The message is sent in plain text preceded by the MD5 digest.  A
           snooper can see the plain-text seed sent by BackupPC and plain-text
           message from the client, but cannot construct a valid MD5 digest
           since the secret $Conf{ServerMesgSecret} is unknown.  A replay
           attack is not possible since the seed changes on a per-connection
           and per-message basis.

       $Conf{MyPath} = ’/bin’;
           PATH setting for BackupPC.  An explicit value is necessary for
           taint mode.  Value shouldn’t matter too much since all execs use
           explicit paths.  However, taint mode in perl will complain if this
           directory is world writable.

       $Conf{UmaskMode} = 027;
           Permission mask for directories and files created by BackupPC.
           Default value prevents any access from group other, and prevents
           group write.

       $Conf{WakeupSchedule} = [1..23];
           Times at which we wake up, check all the PCs, and schedule
           necessary backups.  Times are measured in hours since midnight.
           Can be fractional if necessary (eg: 4.25 means 4:15am).

           If the hosts you are backing up are always connected to the network
           you might have only one or two wakeups each night.  This will keep
           the backup activity after hours.  On the other hand, if you are
           backing up laptops that are only intermittently connected to the
           network you will want to have frequent wakeups (eg: hourly) to
           maximized the chance that each laptop is backed up.

           Examples:

               $Conf{WakeupSchedule} = [22.5];         # once per day at 10:30 pm.
               $Conf{WakeupSchedule} = [1..23];        # every hour except midnight
               $Conf{WakeupSchedule} = [2,4,6,8,10,12,14,16,18,20,22];  # every 2 hours

           The default value is every hour except midnight.

           The first entry of $Conf{WakeupSchedule} is when BackupPC_nightly
           is run.  No other backups can run while BackupPC_nightly is
           running.  You might want to re-arrange the entries in
           $Conf{WakeupSchedule} (they don’t have to be ascending) so that the
           first entry is when you want BackupPC_nightly to run (eg: when you
           don’t expect a lot of regular backups to run).

       $Conf{MaxBackups} = 4;
           Maximum number of simultaneous backups to run.  If there are no
           user backup requests then this is the maximum number of
           simultaneous backups.

       $Conf{MaxUserBackups} = 4;
           Additional number of simultaneous backups that users can run.  As
           many as $Conf{MaxBackups} + $Conf{MaxUserBackups} requests can run
           at the same time.

       $Conf{MaxPendingCmds} = 10;
           Maximum number of pending link commands. New backups will only be
           started if there are no more than $Conf{MaxPendingCmds} plus
           $Conf{MaxBackups} number of pending link commands, plus running
           jobs.  This limit is to make sure BackupPC doesn’t fall too far
           behind in running BackupPC_link commands.

       $Conf{MaxBackupPCNightlyJobs} = 2;
           How many BackupPC_nightly processes to run in parallel.

           Each night, at the first wakeup listed in $Conf{WakeupSchedule},
           BackupPC_nightly is run.  Its job is to remove unneeded files in
           the pool, ie: files that only have one link.  To avoid race
           conditions, BackupPC_nightly runs only when there are no backups
           running, and no backups will start while it runs.

           So to reduce the elapsed time, you might want to increase this
           setting to run several BackupPC_nightly processes in parallel (eg:
           4, or even 8).

       $Conf{BackupPCNightlyPeriod} = 1;
           How many days (runs) it takes BackupPC_nightly to traverse the
           entire pool.  Normally this is 1, which means every night it runs,
           it does traverse the entire pool removing unused pool files.

           Other valid values are 2, 4, 8, 16.  This causes BackupPC_nightly
           to traverse 1/2, 1/4, 1/8 or 1/16th of the pool each night, meaning
           it takes 2, 4, 8 or 16 days to completely traverse the pool.  The
           advantage is that each night the running time of BackupPC_nightly
           is reduced roughly in proportion, since the total job is split over
           multiple days.  The disadvantage is that unused pool files take
           longer to get deleted, which will slightly increase disk usage.

           Note that even when $Conf{BackupPCNightlyPeriod} > 1,
           BackupPC_nightly still runs every night.  It just does less work
           each time it runs.

           Examples:

              $Conf{BackupPCNightlyPeriod} = 1;   # entire pool is checked every night

              $Conf{BackupPCNightlyPeriod} = 2;   # two days to complete pool check
                                                  # (different half each night)

              $Conf{BackupPCNightlyPeriod} = 4;   # four days to complete pool check
                                                  # (different quarter each night)

       $Conf{MaxOldLogFiles} = 14;
           Maximum number of log files we keep around in log directory.  These
           files are aged nightly.  A setting of 14 means the log directory
           will contain about 2 weeks of old log files, in particular at most
           the files LOG, LOG.0, LOG.1, ... LOG.13 (except today’s LOG, these
           files will have a .z extension if compression is on).

           If you decrease this number after BackupPC has been running for a
           while you will have to manually remove the older log files.

       $Conf{DfPath} = ’/bin/df’;
           Full path to the df command.  Security caution: normal users should
           not allowed to write to this file or directory.

       $Conf{DfCmd} = ’$dfPath $topDir’;
           Command to run df.  The following variables are substituted at
           run-time:

             $dfPath      path to df ($Conf{DfPath})
             $topDir      top-level BackupPC data directory

       $Conf{DfMaxUsagePct} = 95;
           Maximum threshold for disk utilization on the __TOPDIR__
           filesystem.  If the output from $Conf{DfPath} reports a percentage
           larger than this number then no new regularly scheduled backups
           will be run.  However, user requested backups (which are usually
           incremental and tend to be small) are still performed, independent
           of disk usage.  Also, currently running backups will not be
           terminated when the disk usage exceeds this number.

       $Conf{TrashCleanSleepSec} = 300;
           How long BackupPC_trashClean sleeps in seconds between each check
           of the trash directory.  Once every 5 minutes should be reasonable.

       $Conf{DHCPAddressRanges} = [];
           List of DHCP address ranges we search looking for PCs to backup.
           This is an array of hashes for each class C address range.  This is
           only needed if hosts in the conf/hosts file have the dhcp flag set.

           Examples:

              # to specify 192.10.10.20 to 192.10.10.250 as the DHCP address pool
              $Conf{DHCPAddressRanges} = [
                  {
                      ipAddrBase => ’192.10.10’,
                      first => 20,
                      last  => 250,
                  },
              ];
              # to specify two pools (192.10.10.20-250 and 192.10.11.10-50)
              $Conf{DHCPAddressRanges} = [
                  {
                      ipAddrBase => ’192.10.10’,
                      first => 20,
                      last  => 250,
                  },
                  {
                      ipAddrBase => ’192.10.11’,
                      first => 10,
                      last  => 50,
                  },
              ];

       $Conf{BackupPCUser} = ’’;
       $Conf{CgiDir} = ’’;
       $Conf{InstallDir} = ’’;
           These configuration settings aren’t used by BackupPC, but simply
           remember a few settings used by configure.pl during installation.
           These are used by configure.pl when upgrading to new versions of
           BackupPC.

       $Conf{BackupPCUserVerify} = 1;
           Whether BackupPC and the CGI script BackupPC_Admin verify that they
           are really running as user $Conf{BackupPCUser}.  If this flag is
           set and the effective user id (euid) differs from
           $Conf{BackupPCUser} then both scripts exit with an error.  This
           catches cases where BackupPC might be accidently started as root or
           the wrong user, or if the CGI script is not installed correctly.

       $Conf{HardLinkMax} = 31999;
           Maximum number of hardlinks supported by the $TopDir file system
           that BackupPC uses.  Most linux or unix file systems should support
           at least 32000 hardlinks per file, or 64000 in other cases.  If a
           pool file already has this number of hardlinks, a new pool file is
           created so that new hardlinks can be accommodated.  This limit will
           only be hit if an identical file appears at least this number of
           times across all the backups.

       What to backup and when to do it

       $Conf{SmbShareName} = ’C$’;
           Name of the host share that is backed up when using SMB.  This can
           be a string or an array of strings if there are multiple shares per
           host.  Examples:

             $Conf{SmbShareName} = ’c’;          # backup ’c’ share
             $Conf{SmbShareName} = [’c’, ’d’];   # backup ’c’ and ’d’ shares

           This setting only matters if $Conf{XferMethod} = ’smb’.

       $Conf{SmbShareUserName} = ’’;
           Smbclient share user name.  This is passed to smbclient’s -U
           argument.

           This setting only matters if $Conf{XferMethod} = ’smb’.

       $Conf{SmbSharePasswd} = ’’;
           Smbclient share password.  This is passed to smbclient via its
           PASSWD environment variable.  There are several ways you can tell
           BackupPC the smb share password.  In each case you should be very
           careful about security.  If you put the password here, make sure
           that this file is not readable by regular users!  See the "Setting
           up config.pl" section in the documentation for more information.

           This setting only matters if $Conf{XferMethod} = ’smb’.

       $Conf{TarShareName} = ’/’;
           Which host directories to backup when using tar transport.  This
           can be a string or an array of strings if there are multiple
           directories to backup per host.  Examples:

             $Conf{TarShareName} = ’/’;                    # backup everything
             $Conf{TarShareName} = ’/home’;                # only backup /home
             $Conf{TarShareName} = [’/home’, ’/src’];      # backup /home and /src

           The fact this parameter is called ’TarShareName’ is for historical
           consistency with the Smb transport options.  You can use any valid
           directory on the client: there is no need for it to correspond to
           any Smb share or device mount point.

           Note also that you can also use $Conf{BackupFilesOnly} to specify a
           specific list of directories to backup.  It’s more efficient to use
           this option instead of $Conf{TarShareName} since a new tar is run
           for each entry in $Conf{TarShareName}.

           On the other hand, if you add --one-file-system to
           $Conf{TarClientCmd} you can backup each file system separately,
           which makes restoring one bad file system easier.  In this case you
           would list all of the mount points here, since you can’t get the
           same result with $Conf{BackupFilesOnly}:

               $Conf{TarShareName} = [’/’, ’/var’, ’/data’, ’/boot’];

           This setting only matters if $Conf{XferMethod} = ’tar’.

       $Conf{FullPeriod} = 6.97;
           Minimum period in days between full backups. A full dump will only
           be done if at least this much time has elapsed since the last full
           dump, and at least $Conf{IncrPeriod} days has elapsed since the
           last successful dump.

           Typically this is set slightly less than an integer number of days.
           The time taken for the backup, plus the granularity of
           $Conf{WakeupSchedule} will make the actual backup interval a bit
           longer.

           There are two special values for $Conf{FullPeriod}:

             -1   Don’t do any regular backups on this machine.  Manually
                  requested backups (via the CGI interface) will still occur.

             -2   Don’t do any backups on this machine.  Manually requested
                  backups (via the CGI interface) will be ignored.

           These special settings are useful for a client that is no longer
           being backed up (eg: a retired machine), but you wish to keep the
           last backups available for browsing or restoring to other machines.

       $Conf{IncrPeriod} = 0.97;
           Minimum period in days between incremental backups (a user
           requested incremental backup will be done anytime on demand).

           Typically this is set slightly less than an integer number of days.
           The time taken for the backup, plus the granularity of
           $Conf{WakeupSchedule} will make the actual backup interval a bit
           longer.

       $Conf{FullKeepCnt} = 1;
           Number of full backups to keep.  Must be >= 1.

           In the steady state, each time a full backup completes successfully
           the oldest one is removed.  If this number is decreased, the extra
           old backups will be removed.

           If filling of incremental dumps is off the oldest backup always has
           to be a full (ie: filled) dump.  This might mean one or two extra
           full dumps are kept until the oldest incremental backups expire.

           Exponential backup expiry is also supported.  This allows you to
           specify:

             - num fulls to keep at intervals of 1 * $Conf{FullPeriod}, followed by
             - num fulls to keep at intervals of 2 * $Conf{FullPeriod},
             - num fulls to keep at intervals of 4 * $Conf{FullPeriod},
             - num fulls to keep at intervals of 8 * $Conf{FullPeriod},
             - num fulls to keep at intervals of 16 * $Conf{FullPeriod},

           and so on.  This works by deleting every other full as each expiry
           boundary is crossed.

           Exponential expiry is specified using an array for
           $Conf{FullKeepCnt}:

             $Conf{FullKeepCnt} = [4, 2, 3];

           Entry #n specifies how many fulls to keep at an interval of 2^n *
           $Conf{FullPeriod} (ie: 1, 2, 4, 8, 16, 32, ...).

           The example above specifies keeping 4 of the most recent full
           backups (1 week interval) two full backups at 2 week intervals, and
           3 full backups at 4 week intervals, eg:

              full 0 19 weeks old   \
              full 1 15 weeks old    >---  3 backups at 4 * $Conf{FullPeriod}
              full 2 11 weeks old   /
              full 3  7 weeks old   \____  2 backups at 2 * $Conf{FullPeriod}
              full 4  5 weeks old   /
              full 5  3 weeks old   \
              full 6  2 weeks old    \___  4 backups at 1 * $Conf{FullPeriod}
              full 7  1 week old     /
              full 8  current       /

           On a given week the spacing might be less than shown as each backup
           ages through each expiry period.  For example, one week later, a
           new full is completed and the oldest is deleted, giving:

              full 0 16 weeks old   \
              full 1 12 weeks old    >---  3 backups at 4 * $Conf{FullPeriod}
              full 2  8 weeks old   /
              full 3  6 weeks old   \____  2 backups at 2 * $Conf{FullPeriod}
              full 4  4 weeks old   /
              full 5  3 weeks old   \
              full 6  2 weeks old    \___  4 backups at 1 * $Conf{FullPeriod}
              full 7  1 week old     /
              full 8  current       /

           You can specify 0 as a count (except in the first entry), and the
           array can be as long as you wish.  For example:

             $Conf{FullKeepCnt} = [4, 0, 4, 0, 0, 2];

           This will keep 10 full dumps, 4 most recent at 1 *
           $Conf{FullPeriod}, followed by 4 at an interval of 4 *
           $Conf{FullPeriod} (approx 1 month apart), and then 2 at an interval
           of 32 * $Conf{FullPeriod} (approx 7-8 months apart).

           Example: these two settings are equivalent and both keep just the
           four most recent full dumps:

              $Conf{FullKeepCnt} = 4;
              $Conf{FullKeepCnt} = [4];

       $Conf{FullKeepCntMin} = 1;
       $Conf{FullAgeMax} = 90;
           Very old full backups are removed after $Conf{FullAgeMax} days.
           However, we keep at least $Conf{FullKeepCntMin} full backups no
           matter how old they are.

           Note that $Conf{FullAgeMax} will be increased to $Conf{FullAgeMax}
           times $Conf{FullPeriod} if $Conf{FullAgeMax} specifies enough full
           backups to exceed $Conf{FullAgeMax}.

       $Conf{IncrKeepCnt} = 6;
           Number of incremental backups to keep.  Must be >= 1.

           In the steady state, each time an incr backup completes
           successfully the oldest one is removed.  If this number is
           decreased, the extra old backups will be removed.

       $Conf{IncrKeepCntMin} = 1;
       $Conf{IncrAgeMax} = 30;
           Very old incremental backups are removed after $Conf{IncrAgeMax}
           days.  However, we keep at least $Conf{IncrKeepCntMin} incremental
           backups no matter how old they are.

       $Conf{PartialAgeMax} = 3;
           A failed full backup is saved as a partial backup.  The rsync
           XferMethod can take advantage of the partial full when the next
           backup is run. This parameter sets the age of the partial full in
           days: if the partial backup is older than this number of days, then
           rsync will ignore (not use) the partial full when the next backup
           is run.  If you set this to a negative value then no partials will
           be saved.  If you set this to 0, partials will be saved, but will
           not be used by the next backup.

           The default setting of 3 days means that a partial older than 3
           days is ignored when the next full backup is done.

       $Conf{IncrFill} = 0;
           Whether incremental backups are filled.  "Filling" means that the
           most recent full (or filled) dump is merged into the new
           incremental dump using hardlinks.  This makes an incremental dump
           look like a full dump.  Prior to v1.03 all incremental backups were
           filled.  In v1.4.0 and later the default is off.

           BackupPC, and the cgi interface in particular, do the right thing
           on un-filled incremental backups.  It will correctly display the
           merged incremental backup with the most recent filled backup,
           giving the un-filled incremental backups a filled appearance.  That
           means it invisible to the user whether incremental dumps are filled
           or not.

           Filling backups takes a little extra disk space, and it does cost
           some extra disk activity for filling, and later removal.  Filling
           is no longer useful, since file mangling and compression doesn’t
           make a filled backup very useful. It’s likely the filling option
           will be removed from future versions: filling will be delegated to
           the display and extraction of backup data.

           If filling is off, BackupPC makes sure that the oldest backup is a
           full, otherwise the following incremental backups will be
           incomplete.  This might mean an extra full backup has to be kept
           until the following incremental backups expire.

           The default is off.  You can turn this on or off at any time
           without affecting existing backups.

       $Conf{RestoreInfoKeepCnt} = 10;
           Number of restore logs to keep.  BackupPC remembers information
           about each restore request.  This number per client will be kept
           around before the oldest ones are pruned.

           Note: files/dirs delivered via Zip or Tar downloads don’t count as
           restores.  Only the first restore option (where the files and dirs
           are written to the host) count as restores that are logged.

       $Conf{ArchiveInfoKeepCnt} = 10;
           Number of archive logs to keep.  BackupPC remembers information
           about each archive request.  This number per archive client will be
           kept around before the oldest ones are pruned.

       $Conf{BackupFilesOnly} = undef;
           List of directories or files to backup.  If this is defined, only
           these directories or files will be backed up.

           For Smb, only one of $Conf{BackupFilesExclude} and
           $Conf{BackupFilesOnly} can be specified per share. If both are set
           for a particular share, then $Conf{BackupFilesOnly} takes
           precedence and $Conf{BackupFilesExclude} is ignored.

           This can be set to a string, an array of strings, or, in the case
           of multiple shares, a hash of strings or arrays.  A hash is used to
           give a list of directories or files to backup for each share (the
           share name is the key).  If this is set to just a string or array,
           and $Conf{SmbShareName} contains multiple share names, then the
           setting is assumed to apply all shares.

           Examples:

              $Conf{BackupFilesOnly} = ’/myFiles’;
              $Conf{BackupFilesOnly} = [’/myFiles’];     # same as first example
              $Conf{BackupFilesOnly} = [’/myFiles’, ’/important’];
              $Conf{BackupFilesOnly} = {
                 ’c’ => [’/myFiles’, ’/important’],      # these are for ’c’ share
                 ’d’ => [’/moreFiles’, ’/archive’],      # these are for ’d’ share
              };

       $Conf{BackupFilesExclude} = undef;
           List of directories or files to exclude from the backup.  For Smb,
           only one of $Conf{BackupFilesExclude} and $Conf{BackupFilesOnly}
           can be specified per share.  If both are set for a particular
           share, then $Conf{BackupFilesOnly} takes precedence and
           $Conf{BackupFilesExclude} is ignored.

           This can be set to a string, an array of strings, or, in the case
           of multiple shares, a hash of strings or arrays.  A hash is used to
           give a list of directories or files to exclude for each share (the
           share name is the key).  If this is set to just a string or array,
           and $Conf{SmbShareName} contains multiple share names, then the
           setting is assumed to apply to all shares.

           The exact behavior is determined by the underlying transport
           program, smbclient or tar.  For smbclient the exlclude file list is
           passed into the X option.  Simple shell wild-cards using "*" or "?"
           are allowed.

           For tar, if the exclude file contains a "/" it is assumed to be
           anchored at the start of the string.  Since all the tar paths start
           with "./", BackupPC prepends a "." if the exclude file starts with
           a "/".  Note that GNU tar version >= 1.13.7 is required for the
           exclude option to work correctly.  For linux or unix machines you
           should add "/proc" to $Conf{BackupFilesExclude} unless you have
           specified --one-file-system in $Conf{TarClientCmd} or
           --one-file-system in $Conf{RsyncArgs}.  Also, for tar, do not use a
           trailing "/" in the directory name: a trailing "/" causes the name
           to not match and the directory will not be excluded.

           Users report that for smbclient you should specify a directory
           followed by "/*", eg: "/proc/*", instead of just "/proc".

           Examples:

              $Conf{BackupFilesExclude} = ’/temp’;
              $Conf{BackupFilesExclude} = [’/temp’];     # same as first example
              $Conf{BackupFilesExclude} = [’/temp’, ’/winnt/tmp’];
              $Conf{BackupFilesExclude} = {
                 ’c’ => [’/temp’, ’/winnt/tmp’],         # these are for ’c’ share
                 ’d’ => [’/junk’, ’/dont_back_this_up’], # these are for ’d’ share
              };

       $Conf{BlackoutBadPingLimit} = 3;
       $Conf{BlackoutGoodCnt} = 7;
           PCs that are always or often on the network can be backed up after
           hours, to reduce PC, network and server load during working hours.
           For each PC a count of consecutive good pings is maintained. Once a
           PC has at least $Conf{BlackoutGoodCnt} consecutive good pings it is
           subject to "blackout" and not backed up during hours and days
           specified by $Conf{BlackoutPeriods}.

           To allow for periodic rebooting of a PC or other brief periods when
           a PC is not on the network, a number of consecutive bad pings is
           allowed before the good ping count is reset. This parameter is
           $Conf{BlackoutBadPingLimit}.

           Note that bad and good pings don’t occur with the same interval. If
           a machine is always on the network, it will only be pinged roughly
           once every $Conf{IncrPeriod} (eg: once per day). So a setting for
           $Conf{BlackoutGoodCnt} of 7 means it will take around 7 days for a
           machine to be subject to blackout. On the other hand, if a ping is
           failed, it will be retried roughly every time BackupPC wakes up,
           eg, every one or two hours. So a setting for
           $Conf{BlackoutBadPingLimit} of 3 means that the PC will lose its
           blackout status after 3-6 hours of unavailability.

           To disable the blackout feature set $Conf{BlackoutGoodCnt} to a
           negative value.  A value of 0 will make all machines subject to
           blackout.  But if you don’t want to do any backups during the day
           it would be easier to just set $Conf{WakeupSchedule} to a
           restricted schedule.

       $Conf{BlackoutPeriods} = [ ... ];
           One or more blackout periods can be specified.  If a client is
           subject to blackout then no regular (non-manual) backups will be
           started during any of these periods.  hourBegin and hourEnd specify
           hours fro midnight and weekDays is a list of days of the week where
           0 is Sunday, 1 is Monday etc.

           For example:

              $Conf{BlackoutPeriods} = [
                   {
                       hourBegin =>  7.0,
                       hourEnd   => 19.5,
                       weekDays  => [1, 2, 3, 4, 5],
                   },
              ];

           specifies one blackout period from 7:00am to 7:30pm local time on
           Mon-Fri.

           The blackout period can also span midnight by setting hourBegin >
           hourEnd, eg:

              $Conf{BlackoutPeriods} = [
                   {
                       hourBegin =>  7.0,
                       hourEnd   => 19.5,
                       weekDays  => [1, 2, 3, 4, 5],
                   },
                   {
                       hourBegin => 23,
                       hourEnd   =>  5,
                       weekDays  => [5, 6],
                   },
              ];

           This specifies one blackout period from 7:00am to 7:30pm local time
           on Mon-Fri, and a second period from 11pm to 5am on Friday and
           Saturday night.

       $Conf{BackupZeroFilesIsFatal} = 1;
           A backup of a share that has zero files is considered fatal. This
           is used to catch miscellaneous Xfer errors that result in no files
           being backed up.  If you have shares that might be empty (and
           therefore an empty backup is valid) you should set this flag to 0.

       General per-PC configuration settings

       $Conf{XferMethod} = ’smb’;
           What transport method to use to backup each host.  If you have a
           mixed set of WinXX and linux/unix hosts you will need to override
           this in the per-PC config.pl.

           The valid values are:

             - ’smb’:     backup and restore via smbclient and the SMB protocol.
                          Easiest choice for WinXX.

             - ’rsync’:   backup and restore via rsync (via rsh or ssh).
                          Best choice for linux/unix.  Good choice also for WinXX.

             - ’rsyncd’:  backup and restore via rsync daemon on the client.
                          Best choice for linux/unix if you have rsyncd running on
                          the client.  Good choice also for WinXX.

             - ’tar’:    backup and restore via tar, tar over ssh, rsh or nfs.
                         Good choice for linux/unix.

             - ’archive’: host is a special archive host.  Backups are not done.
                          An archive host is used to archive other host’s backups
                          to permanent media, such as tape, CDR or DVD.

       $Conf{XferLogLevel} = 1;
           Level of verbosity in Xfer log files.  0 means be quiet, 1 will
           give will give one line per file, 2 will also show skipped files on
           incrementals, higher values give more output.

       $Conf{SmbClientPath} = ’/usr/bin/smbclient’;
           Full path for smbclient. Security caution: normal users should not
           allowed to write to this file or directory.

           smbclient is from the Samba distribution. smbclient is used to
           actually extract the incremental or full dump of the share
           filesystem from the PC.

           This setting only matters if $Conf{XferMethod} = ’smb’.

       $Conf{SmbClientFullCmd} = ’$smbClientPath \\\\$host\\$shareName’ ...
           Command to run smbclient for a full dump.  This setting only
           matters if $Conf{XferMethod} = ’smb’.

           The following variables are substituted at run-time:

              $smbClientPath   same as $Conf{SmbClientPath}
              $host            host to backup/restore
              $hostIP          host IP address
              $shareName       share name
              $userName        user name
              $fileList        list of files to backup (based on exclude/include)
              $I_option        optional -I option to smbclient
              $X_option        exclude option (if $fileList is an exclude list)
              $timeStampFile   start time for incremental dump

       $Conf{SmbClientIncrCmd} = ’$smbClientPath \\\\$host\\$shareName’ ...
           Command to run smbclient for an incremental dump.  This setting
           only matters if $Conf{XferMethod} = ’smb’.

           Same variable substitutions are applied as $Conf{SmbClientFullCmd}.

       $Conf{SmbClientRestoreCmd} = ’$smbClientPath \\\\$host\\$shareName’ ...
           Command to run smbclient for a restore.  This setting only matters
           if $Conf{XferMethod} = ’smb’.

           Same variable substitutions are applied as $Conf{SmbClientFullCmd}.

           If your smb share is read-only then direct restores will fail.  You
           should set $Conf{SmbClientRestoreCmd} to undef and the
           corresponding CGI restore option will be removed.

       $Conf{TarClientCmd} = ’$sshPath -q -x -n -l root $host’ ...
           Full command to run tar on the client.  GNU tar is required.  You
           will need to fill in the correct paths for ssh2 on the local host
           (server) and GNU tar on the client.  Security caution: normal users
           should not allowed to write to these executable files or
           directories.

           See the documentation for more information about setting up ssh2
           keys.

           If you plan to use NFS then tar just runs locally and ssh2 is not
           needed.  For example, assuming the client filesystem is mounted
           below /mnt/hostName, you could use something like:

              $Conf{TarClientCmd} = ’$tarPath -c -v -f - -C /mnt/$host/$shareName’
                                  . ’ --totals’;

           In the case of NFS or rsh you need to make sure BackupPC’s
           privileges are sufficient to read all the files you want to backup.
           Also, you will probably want to add "/proc" to
           $Conf{BackupFilesExclude}.

           The following variables are substituted at run-time:

             $host        host name
             $hostIP      host’s IP address
             $incrDate    newer-than date for incremental backups
             $shareName   share name to backup (ie: top-level directory path)
             $fileList    specific files to backup or exclude
             $tarPath     same as $Conf{TarClientPath}
             $sshPath     same as $Conf{SshPath}

           If a variable is followed by a "+" it is shell escaped.  This is
           necessary for the command part of ssh or rsh, since it ends up
           getting passed through the shell.

           This setting only matters if $Conf{XferMethod} = ’tar’.

       $Conf{TarFullArgs} = ’$fileList+’;
           Extra tar arguments for full backups.  Several variables are
           substituted at run-time.  See $Conf{TarClientCmd} for the list of
           variable substitutions.

           If you are running tar locally (ie: without rsh or ssh) then remove
           the "+" so that the argument is no longer shell escaped.

           This setting only matters if $Conf{XferMethod} = ’tar’.

       $Conf{TarIncrArgs} = ’--newer=$incrDate+ $fileList+’;
           Extra tar arguments for incr backups.  Several variables are
           substituted at run-time.  See $Conf{TarClientCmd} for the list of
           variable substitutions.

           Note that GNU tar has several methods for specifying incremental
           backups, including:

             --newer-mtime $incrDate+
                    This causes a file to be included if the modification time is
                    later than $incrDate (meaning its contents might have changed).
                    But changes in the ownership or modes will not qualify the
                    file to be included in an incremental.

             --newer=$incrDate+
                    This causes the file to be included if any attribute of the
                    file is later than $incrDate, meaning either attributes or
                    the modification time.  This is the default method.  Do
                    not use --atime-preserve in $Conf{TarClientCmd} above,
                    otherwise resetting the atime (access time) counts as an
                    attribute change, meaning the file will always be included
                    in each new incremental dump.

           If you are running tar locally (ie: without rsh or ssh) then remove
           the "+" so that the argument is no longer shell escaped.

           This setting only matters if $Conf{XferMethod} = ’tar’.

       $Conf{TarClientRestoreCmd} = ’$sshPath -q -x -l root $host’ ...
           Full command to run tar for restore on the client.  GNU tar is
           required.  This can be the same as $Conf{TarClientCmd}, with tar’s
           -c replaced by -x and ssh’s -n removed.

           See $Conf{TarClientCmd} for full details.

           This setting only matters if $Conf{XferMethod} = "tar".

           If you want to disable direct restores using tar, you should set
           $Conf{TarClientRestoreCmd} to undef and the corresponding CGI
           restore option will be removed.

       $Conf{TarClientPath} = ’/bin/tar’;
           Full path for tar on the client. Security caution: normal users
           should not allowed to write to this file or directory.

           This setting only matters if $Conf{XferMethod} = ’tar’.

       $Conf{RsyncClientPath} = ’/bin/rsync’;
           Path to rsync executable on the client

       $Conf{RsyncClientCmd} = ’$sshPath -q -x -l root $host $rsyncPath
       $argList+’;
           Full command to run rsync on the client machine.  The following
           variables are substituted at run-time:

                  $host           host name being backed up
                  $hostIP         host’s IP address
                  $shareName      share name to backup (ie: top-level directory path)
                  $rsyncPath      same as $Conf{RsyncClientPath}
                  $sshPath        same as $Conf{SshPath}
                  $argList        argument list, built from $Conf{RsyncArgs},
                                  $shareName, $Conf{BackupFilesExclude} and
                                  $Conf{BackupFilesOnly}

           This setting only matters if $Conf{XferMethod} = ’rsync’.

       $Conf{RsyncClientRestoreCmd} = ’$sshPath -q -x -l root $host $rsyncPath
       $argList+’;
           Full command to run rsync for restore on the client.  The following
           variables are substituted at run-time:

                  $host           host name being backed up
                  $hostIP         host’s IP address
                  $shareName      share name to backup (ie: top-level directory path)
                  $rsyncPath      same as $Conf{RsyncClientPath}
                  $sshPath        same as $Conf{SshPath}
                  $argList        argument list, built from $Conf{RsyncArgs},
                                  $shareName, $Conf{BackupFilesExclude} and
                                  $Conf{BackupFilesOnly}

           This setting only matters if $Conf{XferMethod} = ’rsync’.

       $Conf{RsyncShareName} = ’/’;
           Share name to backup.  For $Conf{XferMethod} = "rsync" this should
           be a file system path, eg ’/’ or ’/home’.

           For $Conf{XferMethod} = "rsyncd" this should be the name of the
           module to backup (ie: the name from /etc/rsynd.conf).

           This can also be a list of multiple file system paths or modules.
           For example, by adding --one-file-system to $Conf{RsyncArgs} you
           can backup each file system separately, which makes restoring one
           bad file system easier.  In this case you would list all of the
           mount points:

               $Conf{RsyncShareName} = [’/’, ’/var’, ’/data’, ’/boot’];

       $Conf{RsyncdClientPort} = 873;
           Rsync daemon port on the client, for $Conf{XferMethod} = "rsyncd".

       $Conf{RsyncdUserName} = ’’;
           Rsync daemon user name on client, for $Conf{XferMethod} = "rsyncd".
           The user name and password are stored on the client in whatever
           file the "secrets file" parameter in rsyncd.conf points to (eg:
           /etc/rsyncd.secrets).

       $Conf{RsyncdPasswd} = ’’;
           Rsync daemon user name on client, for $Conf{XferMethod} = "rsyncd".
           The user name and password are stored on the client in whatever
           file the "secrets file" parameter in rsyncd.conf points to (eg:
           /etc/rsyncd.secrets).

       $Conf{RsyncdAuthRequired} = 1;
           Whether authentication is mandatory when connecting to the client’s
           rsyncd.  By default this is on, ensuring that BackupPC will refuse
           to connect to an rsyncd on the client that is not password
           protected.  Turn off at your own risk.

       $Conf{RsyncCsumCacheVerifyProb} = 0.01;
           When rsync checksum caching is enabled (by adding the
           --checksum-seed=32761 option to $Conf{RsyncArgs}), the cached
           checksums can be occaisonally verified to make sure the file
           contents matches the cached checksums.  This is to avoid the risk
           that disk problems might cause the pool file contents to get
           corrupted, but the cached checksums would make BackupPC think that
           the file still matches the client.

           This setting is the probability (0 means never and 1 means always)
           that a file will be rechecked.  Setting it to 0 means the checksums
           will not be rechecked (unless there is a phase 0 failure).  Setting
           it to 1 (ie: 100%) means all files will be checked, but that is not
           a desirable setting since you are better off simply turning caching
           off (ie: remove the --checksum-seed option).

           The default of 0.01 means 1% (on average) of the files during a
           full backup will have their cached checksum re-checked.

           This setting has no effect unless checksum caching is turned on.

       $Conf{RsyncArgs} = [ ... ];
           Arguments to rsync for backup.  Do not edit the first set unless
           you have a thorough understanding of how File::RsyncP works.

           Examples of additional arguments that should work are
           --exclude/--include, eg:

               $Conf{RsyncArgs} = [
                     # original arguments here
                     ’-v’,
                     ’--exclude’, ’/proc’,
                     ’--exclude’, ’*.tmp’,
               ];

       $Conf{RsyncRestoreArgs} = [ ... ];
           Arguments to rsync for restore.  Do not edit the first set unless
           you have a thorough understanding of how File::RsyncP works.

           If you want to disable direct restores using rsync (eg: is the
           module is read-only), you should set $Conf{RsyncRestoreArgs} to
           undef and the corresponding CGI restore option will be removed.

       $Conf{ArchiveDest} = ’/tmp’;
           Archive Destination

           The Destination of the archive e.g. /tmp for file archive or
           /dev/nst0 for device archive

       $Conf{ArchiveComp} = ’gzip’;
           Archive Compression type

           The valid values are:

             - ’none’:  No Compression

             - ’gzip’:  Medium Compression. Recommended.

             - ’bzip2’: High Compression but takes longer.

       $Conf{ArchivePar} = 0;
           Archive Parity Files

           The amount of Parity data to generate, as a percentage of the
           archive size.  Uses the commandline par2 (par2cmdline) available
           from http://parchive.sourceforge.net

           Only useful for file dumps.

           Set to 0 to disable this feature.

       $Conf{ArchiveSplit} = 0;
           Archive Size Split

           Only for file archives. Splits the output into the specified size *
           1,000,000.  e.g. to split into 650,000,000 bytes, specify 650
           below.

           If the value is 0, or if $Conf{ArchiveDest} is an existing file or
           device (e.g. a streaming tape drive), this feature is disabled.

       $Conf{ArchiveClientCmd} = ’$Installdir/bin/BackupPC_archiveHost’ ...
           Archive Command

           This is the command that is called to actually run the archive
           process for each host.  The following variables are substituted at
           run-time:

             $Installdir    The installation directory of BackupPC
             $tarCreatePath The path to BackupPC_tarCreate
             $splitpath     The path to the split program
             $parpath       The path to the par2 program
             $host          The host to archive
             $backupnumber  The backup number of the host to archive
             $compression   The path to the compression program
             $compext       The extension assigned to the compression type
             $splitsize     The number of bytes to split archives into
             $archiveloc    The location to put the archive
             $parfile       The amount of parity data to create (percentage)

       $Conf{SshPath} = ’/usr/bin/ssh’;
           Full path for ssh. Security caution: normal users should not
           allowed to write to this file or directory.

       $Conf{NmbLookupPath} = ’/usr/bin/nmblookup’;
           Full path for nmblookup. Security caution: normal users should not
           allowed to write to this file or directory.

           nmblookup is from the Samba distribution. nmblookup is used to get
           the netbios name, necessary for DHCP hosts.

       $Conf{NmbLookupCmd} = ’$nmbLookupPath -A $host’;
           NmbLookup command.  Given an IP address, does an nmblookup on that
           IP address.  The following variables are substituted at run-time:

             $nmbLookupPath      path to nmblookup ($Conf{NmbLookupPath})
             $host               IP address

           This command is only used for DHCP hosts: given an IP address, this
           command should try to find its NetBios name.

       $Conf{NmbLookupFindHostCmd} = ’$nmbLookupPath $host’;
           NmbLookup command.  Given a netbios name, finds that host by doing
           a NetBios lookup.  Several variables are substituted at run-time:

             $nmbLookupPath      path to nmblookup ($Conf{NmbLookupPath})
             $host               NetBios name

           In some cases you might need to change the broadcast address, for
           example if nmblookup uses 192.168.255.255 by default and you find
           that doesn’t work, try 192.168.1.255 (or your equivalent class C
           address) using the -B option:

              $Conf{NmbLookupFindHostCmd} = ’$nmbLookupPath -B 192.168.1.255 $host’;

           If you use a WINS server and your machines don’t respond to
           multicast NetBios requests you can use this (replace 1.2.3.4 with
           the IP address of your WINS server):

              $Conf{NmbLookupFindHostCmd} = ’$nmbLookupPath -R -U 1.2.3.4 $host’;

           This is preferred over multicast since it minimizes network
           traffic.

           Experiment manually for your site to see what form of nmblookup
           command works.

       $Conf{FixedIPNetBiosNameCheck} = 0;
           For fixed IP address hosts, BackupPC_dump can also verify the
           netbios name to ensure it matches the host name.  An error is
           generated if they do not match.  Typically this flag is off.  But
           if you are going to transition a bunch of machines from fixed host
           addresses to DHCP, setting this flag is a great way to verify that
           the machines have their netbios name set correctly before turning
           on DCHP.

       $Conf{PingPath} = ’/bin/ping’;
           Full path to the ping command.  Security caution: normal users
           should not be allowed to write to this file or directory.

           If you want to disable ping checking, set this to some program that
           exits with 0 status, eg:

               $Conf{PingPath} = ’/bin/echo’;

       $Conf{PingCmd} = ’$pingPath -c 1 $host’;
           Ping command.  The following variables are substituted at run-time:

             $pingPath      path to ping ($Conf{PingPath})
             $host          host name

           Wade Brown reports that on solaris 2.6 and 2.7 ping -s returns the
           wrong exit status (0 even on failure).  Replace with "ping $host
           1", which gets the correct exit status but we don’t get the round-
           trip time.

       $Conf{ServerInitdPath} = ’’;
       $Conf{ServerInitdStartCmd} = ’’;
           Path to init.d script and command to use that script to start the
           server from the CGI interface.  The following variables are
           substituted at run-time:

             $sshPath           path to ssh ($Conf{SshPath})
             $serverHost        same as $Conf{ServerHost}
             $serverInitdPath   path to init.d script ($Conf{ServerInitdPath})

           Example:

           $Conf{ServerInitdPath}     = ’/etc/init.d/backuppc’;
           $Conf{ServerInitdStartCmd} = ’$sshPath -q -x -l root $serverHost’
                                      . ’ $serverInitdPath start’
                                      . ’ < /dev/null >& /dev/null’;

       $Conf{CompressLevel} = 0;
           Compression level to use on files.  0 means no compression.
           Compression levels can be from 1 (least cpu time, slightly worse
           compression) to 9 (most cpu time, slightly better compression).
           The recommended value is 3.  Changing to 5, for example, will take
           maybe 20% more cpu time and will get another 2-3% additional
           compression. See the zlib documentation for more information about
           compression levels.

           Changing compression on or off after backups have already been done
           will require both compressed and uncompressed pool files to be
           stored.  This will increase the pool storage requirements, at least
           until all the old backups expire and are deleted.

           It is ok to change the compression value (from one non-zero value
           to another non-zero value) after dumps are already done.  Since
           BackupPC matches pool files by comparing the uncompressed versions,
           it will still correctly match new incoming files against existing
           pool files.  The new compression level will take effect only for
           new files that are newly compressed and added to the pool.

           If compression was off and you are enabling compression for the
           first time you can use the BackupPC_compressPool utility to
           compress the pool.  This avoids having the pool grow to accommodate
           both compressed and uncompressed backups.  See the documentation
           for more information.

           Note: compression needs the Compress::Zlib perl library.  If the
           Compress::Zlib library can’t be found then $Conf{CompressLevel} is
           forced to 0 (compression off).

       $Conf{PingMaxMsec} = 20;
           Maximum round-trip ping time in milliseconds.  This threshold is
           set to avoid backing up PCs that are remotely connected through WAN
           or dialup connections.  The output from ping -s (assuming it is
           supported on your system) is used to check the round-trip packet
           time.  On your local LAN round-trip times should be much less than
           20msec.  On most WAN or dialup connections the round-trip time will
           be typically more than 20msec.  Tune if necessary.

       $Conf{ClientTimeout} = 72000;
           Timeout in seconds when listening for the transport program’s
           (smbclient, tar etc) stdout. If no output is received during this
           time, then it is assumed that something has wedged during a backup,
           and the backup is terminated.

           Note that stdout buffering combined with huge files being backed up
           could cause longish delays in the output from smbclient that
           BackupPC_dump sees, so in rare cases you might want to increase
           this value.

           Despite the name, this parameter sets the timeout for all transport
           methods (tar, smb etc).

       $Conf{MaxOldPerPCLogFiles} = 12;
           Maximum number of log files we keep around in each PC’s directory
           (ie: pc/$host).  These files are aged monthly.  A setting of 12
           means there will be at most the files LOG, LOG.0, LOG.1, ... LOG.11
           in the pc/$host directory (ie: about a years worth).  (Except this
           month’s LOG, these files will have a .z extension if compression is
           on).

           If you decrease this number after BackupPC has been running for a
           while you will have to manually remove the older log files.

       $Conf{DumpPreUserCmd} = undef;
       $Conf{DumpPostUserCmd} = undef;
       $Conf{RestorePreUserCmd} = undef;
       $Conf{RestorePostUserCmd} = undef;
       $Conf{ArchivePreUserCmd} = undef;
       $Conf{ArchivePostUserCmd} = undef;
           Optional commands to run before and after dumps and restores.
           Stdout from these commands will be written to the Xfer (or Restore)
           log file.  One example of using these commands would be to shut
           down and restart a database server, or to dump a database to files
           for backup.  Example:

              $Conf{DumpPreUserCmd} = ’$sshPath -q -x -l root $host /usr/bin/dumpMysql’;

           The following variable substitutions are made at run time for
           $Conf{DumpPreUserCmd} and $Conf{DumpPostUserCmd}:

                  $type         type of dump (incr or full)
                  $xferOK       1 if the dump succeeded, 0 if it didn’t
                  $client       client name being backed up
                  $host         host name (could be different from client name if
                                           $Conf{ClientNameAlias} is set)
                  $hostIP       IP address of host
                  $user         user name from the hosts file
                  $moreUsers    list of additional users from the hosts file
                  $share        the first share name
                  $shares       list of all the share names
                  $XferMethod   value of $Conf{XferMethod} (eg: tar, rsync, smb)
                  $sshPath      value of $Conf{SshPath},
                  $cmdType      set to DumpPreUserCmd or DumpPostUserCmd

           The following variable substitutions are made at run time for
           $Conf{RestorePreUserCmd} and $Conf{RestorePostUserCmd}:

                  $client       client name being backed up
                  $xferOK       1 if the restore succeeded, 0 if it didn’t
                  $host         host name (could be different from client name if
                                           $Conf{ClientNameAlias} is set)
                  $hostIP       IP address of host
                  $user         user name from the hosts file
                  $moreUsers    list of additional users from the hosts file
                  $share        the first share name
                  $XferMethod   value of $Conf{XferMethod} (eg: tar, rsync, smb)
                  $sshPath      value of $Conf{SshPath},
                  $type         set to "restore"
                  $bkupSrcHost  host name of the restore source
                  $bkupSrcShare share name of the restore source
                  $bkupSrcNum   backup number of the restore source
                  $pathHdrSrc   common starting path of restore source
                  $pathHdrDest  common starting path of destination
                  $fileList     list of files being restored
                  $cmdType      set to RestorePreUserCmd or RestorePostUserCmd

           The following variable substitutions are made at run time for
           $Conf{ArchivePreUserCmd} and $Conf{ArchivePostUserCmd}:

                  $client       client name being backed up
                  $xferOK       1 if the archive succeeded, 0 if it didn’t
                  $host         Name of the archive host
                  $user         user name from the hosts file
                  $share        the first share name
                  $XferMethod   value of $Conf{XferMethod} (eg: tar, rsync, smb)
                  $HostList     list of hosts being archived
                  $BackupList   list of backup numbers for the hosts being archived
                  $archiveloc   location where the archive is sent to
                  $parfile      amount of parity data being generated (percentage)
                  $compression  compression program being used (eg: cat, gzip, bzip2)
                  $compext      extension used for compression type (eg: raw, gz, bz2)
                  $splitsize    size of the files that the archive creates
                  $sshPath      value of $Conf{SshPath},
                  $type         set to "archive"
                  $cmdType      set to ArchivePreUserCmd or ArchivePostUserCmd

       $Conf{ClientNameAlias} = undef;
           Override the client’s host name.  This allows multiple clients to
           all refer to the same physical host.  This should only be set in
           the per-PC config file and is only used by BackupPC at the last
           moment prior to generating the command used to backup that machine
           (ie: the value of $Conf{ClientNameAlias} is invisible everywhere
           else in BackupPC).  The setting can be a host name or IP address,
           eg:

                   $Conf{ClientNameAlias} = ’realHostName’;
                   $Conf{ClientNameAlias} = ’192.1.1.15’;

           will cause the relevant smb/tar/rsync backup/restore commands to be
           directed to realHostName, not the client name.

           Note: this setting doesn’t work for hosts with DHCP set to 1.

       $Conf{PerlModuleLoad} = undef;
           Advanced option for asking BackupPC to load additional perl
           modules.  Can be a list (array ref) of module names to load at
           startup.

       Email reminders, status and messages

       $Conf{SendmailPath} = ’/usr/sbin/sendmail’;
           Full path to the sendmail command.  Security caution: normal users
           should not allowed to write to this file or directory.

       $Conf{EMailNotifyMinDays} = 2.5;
           Minimum period between consecutive emails to a single user.  This
           tries to keep annoying email to users to a reasonable level.  Email
           checks are done nightly, so this number is effectively rounded up
           (ie: 2.5 means a user will never receive email more than once every
           3 days).

       $Conf{EMailFromUserName} = ’’;
           Name to use as the "from" name for email.  Depending upon your mail
           handler this is either a plain name (eg: "admin") or a fully-
           qualified name (eg: "admin@mydomain.com").

       $Conf{EMailAdminUserName} = ’’;
           Destination address to an administrative user who will receive a
           nightly email with warnings and errors.  If there are no warnings
           or errors then no email will be sent.  Depending upon your mail
           handler this is either a plain name (eg: "admin") or a fully-
           qualified name (eg: "admin@mydomain.com").

       $Conf{EMailUserDestDomain} = ’’;
           Destination domain name for email sent to users.  By default this
           is empty, meaning email is sent to plain, unqualified addresses.
           Otherwise, set it to the destintation domain, eg:

              $Cong{EMailUserDestDomain} = ’@mydomain.com’;

           With this setting user email will be set to ’user@mydomain.com’.

       $Conf{EMailNoBackupEverSubj} = undef;
       $Conf{EMailNoBackupEverMesg} = undef;
           This subject and message is sent to a user if their PC has never
           been backed up.

           These values are language-dependent.  The default versions can be
           found in the language file (eg: lib/BackupPC/Lang/en.pm).  If you
           need to change the message, copy it here and edit it, eg:

             $Conf{EMailNoBackupEverMesg} = <<’EOF’;
             To: $user$domain
             cc:
             Subject: $subj
             $headers
             Dear $userName,

             This is a site-specific email message.
             EOF

       $Conf{EMailNotifyOldBackupDays} = 7.0;
           How old the most recent backup has to be before notifying user.
           When there have been no backups in this number of days the user is
           sent an email.

       $Conf{EMailNoBackupRecentSubj} = undef;
       $Conf{EMailNoBackupRecentMesg} = undef;
           This subject and message is sent to a user if their PC has not
           recently been backed up (ie: more than
           $Conf{EMailNotifyOldBackupDays} days ago).

           These values are language-dependent.  The default versions can be
           found in the language file (eg: lib/BackupPC/Lang/en.pm).  If you
           need to change the message, copy it here and edit it, eg:

             $Conf{EMailNoBackupRecentMesg} = <<’EOF’;
             To: $user$domain
             cc:
             Subject: $subj
             $headers
             Dear $userName,

             This is a site-specific email message.
             EOF

       $Conf{EMailNotifyOldOutlookDays} = 5.0;
           How old the most recent backup of Outlook files has to be before
           notifying user.

       $Conf{EMailOutlookBackupSubj} = undef;
       $Conf{EMailOutlookBackupMesg} = undef;
           This subject and message is sent to a user if their Outlook files
           have not recently been backed up (ie: more than
           $Conf{EMailNotifyOldOutlookDays} days ago).

           These values are language-dependent.  The default versions can be
           found in the language file (eg: lib/BackupPC/Lang/en.pm).  If you
           need to change the message, copy it here and edit it, eg:

             $Conf{EMailOutlookBackupMesg} = <<’EOF’;
             To: $user$domain
             cc:
             Subject: $subj
             $headers
             Dear $userName,

             This is a site-specific email message.
             EOF

       CGI user interface configuration settings

       $Conf{CgiAdminUserGroup} = ’’;
       $Conf{CgiAdminUsers} = ’’;
           Normal users can only access information specific to their host.
           They can start/stop/browse/restore backups.

           Administrative users have full access to all hosts, plus overall
           status and log information.

           The administrative users are the union of the unix/linux group
           $Conf{CgiAdminUserGroup} and the manual list of users, separated by
           spaces, in $Conf{CgiAdminUsers}. If you don’t want a group or
           manual list of users set the corresponding configuration setting to
           undef or an empty string.

           If you want every user to have admin privileges (careful!), set
           $Conf{CgiAdminUsers} = ’*’.

           Examples:

              $Conf{CgiAdminUserGroup} = ’admin’;
              $Conf{CgiAdminUsers}     = ’craig celia’;
              --> administrative users are the union of group admin, plus
                craig and celia.

              $Conf{CgiAdminUserGroup} = ’’;
              $Conf{CgiAdminUsers}     = ’craig celia’;
              --> administrative users are only craig and celia’.

       $Conf{CgiURL} = undef;
           URL of the BackupPC_Admin CGI script.  Used for email messages.

       $Conf{Language} = ’en’;
           Language to use.  See lib/BackupPC/Lang for the list of supported
           languages, which include English (en), French (fr), Spanish (es),
           German (de), Italian (it) and Dutch (nl).

           Currently the Language setting applies to the CGI interface and
           email messages sent to users.  Log files and other text are still
           in English.

       $Conf{CgiUserHomePageCheck} = ’’;
       $Conf{CgiUserUrlCreate} = ’mailto:%s’;
           User names that are rendered by the CGI interface can be turned
           into links into their home page or other information about the
           user.  To set this up you need to create two sprintf() strings,
           that each contain a single ’%s’ that will be replaced by the user
           name.  The default is a mailto: link.

           $Conf{CgiUserHomePageCheck} should be an absolute file path that is
           used to check (via "-f") that the user has a valid home page.  Set
           this to undef or an empty string to turn off this check.

           $Conf{CgiUserUrlCreate} should be a full URL that points to the
           user’s home page.  Set this to undef or an empty string to turn off
           generation of URLs for user names.

           Example:

              $Conf{CgiUserHomePageCheck} = ’/var/www/html/users/%s.html’;
              $Conf{CgiUserUrlCreate}     = ’http://myhost/users/%s.html’;
              --> if /var/www/html/users/craig.html exists, then ’craig’ will
                be rendered as a link to http://myhost/users/craig.html.

       $Conf{CgiDateFormatMMDD} = 1;
           Date display format for CGI interface.  True for US-style dates
           (MM/DD) and zero for international dates (DD/MM).

       $Conf{CgiNavBarAdminAllHosts} = 1;
           If set, the complete list of hosts appears in the left navigation
           bar pull-down for administrators.  Otherwise, just the hosts for
           which the user is listed in the host file (as either the user or in
           moreUsers) are displayed.

       $Conf{CgiSearchBoxEnable} = 1;
           Enable/disable the search box in the navigation bar.

       $Conf{CgiNavBarLinks} = [ ... ];
           Additional navigation bar links.  These appear for both regular
           users and administrators.  This is a list of hashes giving the link
           (URL) and the text (name) for the link.  Specifying lname instead
           of name uses the language specific string (ie: $Lang->{lname})
           instead of just literally displaying name.

       $Conf{CgiStatusHilightColor} = { ...
           Hilight colors based on status that are used in the PC summary
           page.

       $Conf{CgiHeaders} = ’<meta http-equiv="pragma" content="no-cache">’;
           Additional CGI header text.

       $Conf{CgiImageDir} = ’’;
           Directory where images are stored.  This directory should be below
           Apache’s DocumentRoot.  This value isn’t used by BackupPC but is
           used by configure.pl when you upgrade BackupPC.

           Example:

               $Conf{CgiImageDir} = ’/usr/local/apache/htdocs/BackupPC’;

       $Conf{CgiExt2ContentType} = { };
           Additional mappings of file name extenions to Content-Type for
           individual file restore.  See $Ext2ContentType in BackupPC_Admin
           for the default setting.  You can add additional settings here, or
           override any default settings.  Example:

               $Conf{CgiExt2ContentType} = {
                           ’pl’  => ’text/plain’,
                    };

       $Conf{CgiImageDirURL} = ’’;
           URL (without the leading http://host) for BackupPC’s image
           directory.  The CGI script uses this value to serve up image files.

           Example:

               $Conf{CgiImageDirURL} = ’/BackupPC’;

       $Conf{CgiCSSFile} = ’BackupPC_stnd.css’;
           CSS stylesheet for the CGI interface.  It is stored in the
           $Conf{CgiImageDir} directory and accessed via the
           $Conf{CgiImageDirURL} URL.

Version Numbers

       Starting with v1.4.0 BackupPC uses a X.Y.Z version numbering system,
       instead of X.0Y. The first digit is for major new releases, the middle
       digit is for significant feature releases and improvements (most of the
       releases have been in this category), and the last digit is for bug
       fixes. You should think of the old 1.00, 1.01, 1.02 and 1.03 as 1..0,
       1.1.0, 1.2.0 and 1.3.0.

       Additionally, patches might be made available.  A patched version
       number is of the form X.Y.ZplN (eg: 2.1.0pl2), where N is the patch
       level.

Author

       Craig Barratt  <cbarratt@users.sourceforge.net>

       See <http://backuppc.sourceforge.net>.

Copyright

       Copyright (C) 2001-2005 Craig Barratt

Credits

       Ryan Kucera contributed the directory navigation code and images for
       v1.5.0.  He contributed the first skeleton of BackupPC_restore.  He
       also added a significant revision to the CGI interface, including CSS
       tags, in v2.1.0, and designed the BackupPC logo.

       Xavier Nicollet, with additions from Guillaume Filion, added the
       internationalization (i18n) support to the CGI interface for v2.0.0.
       Xavier provided the French translation fr.pm, with additions from
       Guillaume.

       Guillaume Filion wrote BackupPC_zipCreate and added the CGI support for
       zip download, in addition to some CGI cleanup, for v1.5.0.  Guillaume
       continues to support fr.pm updates for each new version.

       Josh Marshall implemented the Archive feature in v2.1.0.

       Ludovic Drolez supports the BackupPC Debian package.

       Javier Gonzalez provided the Spanish translation, es.pm for v2.0.0.

       Manfred Herrmann provided the German translation, de.pm for v2.0.0.
       Manfred continues to support de.pm updates for each new version,
       together with some help frmo Ralph Paßgang.

       Lorenzo Cappelletti provided the Italian translation, it.pm for v2.1.0.

       Lieven Bridts provided the Dutch translation, nl.pm, for v2.1.0, with
       some tweaks from Guus Houtzager.

       Many people have reported bugs, made useful suggestions and helped with
       testing; see the ChangeLog and the mail lists.

       Your name could appear here in the next version!

License

       This program is free software; you can redistribute it and/or modify it
       under the terms of the GNU General Public License as published by the
       Free Software Foundation; either version 2 of the License, or (at your
       option) any later version.

       This program is distributed in the hope that it will be useful, but
       WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
       General Public License for more details.

       You should have received a copy of the GNU General Public License in
       the LICENSE file along with this program; if not, write to the Free
       Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
       02111-1307 USA.