Provided by: dump_0.4b47-3_amd64 
NAME
dump - ext2/3/4 filesystem backup
SYNOPSIS
dump [-level#] [-ackMnqSuv] [-A file] [-B records] [-b blocksize] [-d density] [-D file]
[-e inode numbers] [-E file] [-f file] [-F script] [-h level] [-I nr errors]
[-jcompression level] [-L label] [-Q file] [-s feet] [-T date] [-y] [-zcompression level]
files-to-dump
dump [-W | -w]
DESCRIPTION
Dump examines files on an ext2/3/4 filesystem and determines which files need to be backed
up. These files are copied to the given disk, tape or other storage medium for safe
keeping (see the -f option below for doing remote backups). A dump that is larger than the
output medium is broken into multiple volumes. On most media the size is determined by
writing until an end-of-media indication is returned.
On media that cannot reliably return an end-of-media indication (such as some cartridge
tape drives), each volume is of a fixed size; the actual size is determined by specifying
cartridge media, or via the tape size, density and/or block count options below. By
default, the same output file name is used for each volume after prompting the operator to
change media.
files-to-dump is either a mountpoint of a filesystem or a list of files and directories to
be backed up as a subset of a filesystem. In the former case, either the path to a mounted
filesystem or the device of an unmounted filesystem can be used. In the latter case,
certain restrictions are placed on the backup: -u is not allowed, the only dump level that
is supported is 0 and all the files and directories must reside on the same filesystem.
OPTIONS
The following options are supported by dump:
-level#
The dump level (any integer). A level 0, full backup, specified by -0 guarantees
the entire file system is copied (but see also the -h option below). A level number
above 0, incremental backup, tells dump to copy all files new or modified since the
last dump of a lower level. The default level is 0. Historically only levels 0 to 9
were usable in dump, this version is able to understand any integer as a dump
level.
-a “auto-size”. Bypass all tape length calculations, and write until an end-of-media
indication is returned. This works best for most modern tape drives, and is the
default. Use of this option is particularly recommended when appending to an
existing tape, or using a tape drive with hardware compression (where you can never
be sure about the compression ratio).
-A archive_file
Archive a dump table-of-contents in the specified archive_file to be used by
restore(8) to determine whether a file is in the dump file that is being restored.
-b blocksize
The number of kilobytes per dump record. The default blocksize is 10, unless the -d
option has been used to specify a tape density of 6250BPI or more, in which case
the default blocksize is 32. Th maximal value is 1024. Note however that, since
the IO system slices all requests into chunks of MAXBSIZE (which can be as low as
64kB), you can experience problems with dump(8) and restore(8) when using a higher
value, depending on your kernel and/or libC versions.
-B records
The number of 1 kB blocks per volume. Not normally required, as dump can detect
end-of-media. When the specified size is reached, dump waits for you to change the
volume. This option overrides the calculation of tape size based on length and
density. If compression is on this limits the size of the compressed output per
volume. Multiple values may be given as a single argument separated by commas.
Each value will be used for one dump volume in the order listed; if dump creates
more volumes than the number of values given, the last value will be used for the
remaining volumes. This is useful for filling up already partially filled media
(and then continuing with full size volumes on empty media) or mixing media of
different sizes.
-c Change the defaults for use with a cartridge tape drive, with a density of 8000
bpi, and a length of 1700 feet. Specifying a cartridge drive overrides the end-of-
media detection.
-d density
Set tape density to density. The default is 1600BPI. Specifying a tape density
overrides the end-of-media detection.
-D file
Set the path name of the file storing the information about the previous full and
incremental dumps. The default location is /var/lib/dumpdates.
-e inodes
Exclude inodes from the dump. The inodes parameter is a comma separated list of
inode numbers (you can use stat(1) to find the inode number for a file or
directory).
-E file
Read list of inodes to be excluded from the dump from the text file file. The file
file should be an ordinary file containing inode numbers separated by newlines.
-f file
Write the backup to file; file may be a special device file like /dev/st0 (a tape
drive), /dev/rsd1c (a floppy disk drive), an ordinary file, or - (the standard
output). Multiple file names may be given as a single argument separated by commas.
Each file will be used for one dump volume in the order listed; if the dump
requires more volumes than the number of names given, the last file name will used
for all remaining volumes after prompting for media changes. If the name of the
file is of the form host:file or user@host:file dump writes to the named file on
the remote host (which should already exist, dump doesn't create a new remote file)
using rmt(8). The default path name of the remote rmt(8) program is /etc/rmt; this
can be overridden by the environment variable RMT.
-F script
Run script at the end of each tape (except for the last one). The device name and
the current volume number are passed on the command line. The script must return 0
if dump should continue without asking the user to change the tape, 1 if dump
should continue but ask the user to change the tape. Any other exit code will cause
dump to abort. For security reasons, dump reverts back to the real user ID and the
real group ID before running the script.
-h level
Honor the user nodump flag UF_NODUMP only for dumps at or above the given level.
The default honor level is 1, so that incremental backups omit such files but full
backups retain them.
-I nr errors
By default, dump will ignore the first 32 read errors on the file system before
asking for operator intervention. You can change this using this flag to any value.
This is useful when running dump on an active filesystem where read errors simply
indicate an inconsistency between the mapping and dumping passes.
A value of 0 means that all read errors will be ignored.
-jcompression level
Compress every block to be written on the tape using bzlib library. This option
will work only when dumping to a file or pipe or, when dumping to a tape drive, if
the tape drive is capable of writing variable length blocks. You will need at least
the 0.4b24 version of restore in order to extract compressed tapes. Tapes written
using compression will not be compatible with the BSD tape format. The (optional)
parameter specifies the compression level bzlib will use. The default compression
level is 2. If the optional parameter is specified, there should be no white space
between the option letter and the parameter.
-k Use Kerberos authentication to talk to remote tape servers. (Only available if this
option was enabled when dump was compiled.)
-L label
The user-supplied text string label is placed into the dump header, where tools
like restore(8) and file(8) can access it. Note that this label is limited to be at
most LBLSIZE (currently 16) characters, which must include the terminating \0.
-m If this flag is specified, dump will optimise the output for inodes having been
changed but not modified since the last dump ('changed' and 'modified' have the
meaning defined in stat(2) ). For those inodes, dump will save only the metadata,
instead of saving the entire inode contents. Inodes which are either directories
or have been modified since the last dump are saved in a regular way. Uses of this
flag must be consistent, meaning that either every dump in an incremental dump set
have the flag, or no one has it.
If you use this option, be aware that many programs that unpack files from archives
(e.g. tar, rpm, unzip, dpkg) may set files' mtimes to dates in the past. Files
installed in this way may not be dumped correctly using "dump -m" if the modified
mtime is earlier than the previous level dump.
Tapes written using such 'metadata only' inodes will not be compatible with the BSD
tape format or older versions of restore.
-M Enable the multi-volume feature. The name specified with f is treated as a prefix
and dump writes in sequence to <prefix>001, <prefix>002 etc. This can be useful
when dumping to files on an ext2/3/4 partition, in order to bypass the 2GB file
size limitation.
-n Whenever dump requires operator attention, notify all operators in the group
operator by means similar to a wall(1).
-q Make dump abort immediately whenever operator attention is required, without
prompting in case of write errors, tape changes etc.
-Q file
Enable the Quick File Access support. Tape positions for each inode are stored into
the file file which is used by restore (if called with parameter -Q and the
filename) to directly position the tape at the file restore is currently working
on. This saves hours when restoring single files from large backups, saves the
tapes and the drive's head.
It is recommended to set up the st driver to return logical tape positions rather
than physical before calling dump/restore with parameter -Q. Since not all tape
devices support physical tape positions those tape devices return an error during
dump/restore when the st driver is set to the default physical setting. Please see
the st(4) man page, option MTSETDRVBUFFER , or the mt(1) man page, on how to set
the driver to return logical tape positions.
Before calling restore with parameter -Q, always make sure the st driver is set to
return the same type of tape position used during the call to dump. Otherwise
restore may be confused.
This option can be used when dumping to local tapes (see above) or to local files.
-s feet
Attempt to calculate the amount of tape needed at a particular density. If this
amount is exceeded, dump prompts for a new tape. It is recommended to be a bit
conservative on this option. The default tape length is 2300 feet. Specifying the
tape size overrides end-of-media detection.
-S Size estimate. Determine the amount of space that is needed to perform the dump
without actually doing it, and display the estimated number of bytes it will take.
This is useful with incremental dumps to determine how many volumes of media will
be needed.
-T date
Use the specified date as the starting time for the dump instead of the time
determined from looking in /var/lib/dumpdates . The format of date is the same as
that of ctime(3) followed by an rfc822 timezone specification: either a plus or
minus sign followed by two digits for the number of hours and two digits for the
minutes. For example, -0800 for eight hours west of Greenwich or +0230 for two
hours and a half east of Greenwich. This timezone offset takes into account
daylight savings time (if applicable to the timezone): UTC offsets when daylight
savings time is in effect will be different than offsets when daylight savings time
is not in effect. For backward compatibility, if no timezone is specified, a local
time is assumed. This option is useful for automated dump scripts that wish to
dump over a specific period of time. The -T option is mutually exclusive from the
-u option.
-u Update the file /var/lib/dumpdates after a successful dump. The format of
/var/lib/dumpdates is readable by people, consisting of one free format record per
line: filesystem name, increment level and ctime(3) format dump date followed by a
rfc822 timezone specification (see the -u option for details). If no timezone
offset is specified, times are interpreted as local. Whenever the file is written,
all dates in the file are converted to the local time zone, without changing the
UTC times. There may be only one entry per filesystem at each level. The file
/var/lib/dumpdates may be edited to change any of the fields, if necessary.
-v The -v (verbose) makes dump to print extra information which could be helpful in
debug sessions.
-W Dump tells the operator what file systems need to be dumped. This information is
gleaned from the files /var/lib/dumpdates and /etc/fstab. The -W option causes
dump to print out, for all file systems in /var/lib/dumpdates , and recognized file
systems in /etc/mtab and /etc/fstab. the most recent dump date and level, and
highlights those that should be dumped. If the -W option is set, all other options
are ignored, and dump exits immediately.
-w Is like -W, but prints only recognized filesystems in /etc/mtab and /etc/fstab
which need to be dumped.
-y Compress every block to be written to the tape using the lzo library. This doesn't
compress as well as the zlib library but it's much faster. This option will work
only when dumping to a file or pipe or, when dumping to a tape drive, if the tape
drive is capable of writing variable length blocks. You will need at least the
0.4b34 version of restore in order to extract compressed tapes. Tapes written using
compression will not be compatible with the BSD tape format.
-zcompression level
Compress every block to be written on the tape using zlib library. This option will
work only when dumping to a file or pipe or, when dumping to a tape drive, if the
tape drive is capable of writing variable length blocks. You will need at least the
0.4b22 version of restore in order to extract compressed tapes. Tapes written using
compression will not be compatible with the BSD tape format. The (optional)
parameter specifies the compression level zlib will use. The default compression
level is 2. If the optional parameter is specified, there should be no white space
between the option letter and the parameter.
Dump requires operator intervention on these conditions: end of tape, end of dump, tape
write error, tape open error or disk read error (if there is more than a threshold of nr
errors). In addition to alerting all operators implied by the -n key, dump interacts with
the operator on dump's control terminal at times when dump can no longer proceed, or if
something is grossly wrong. All questions dump poses must be answered by typing “yes” or
“no”, appropriately.
Since making a dump involves a lot of time and effort for full dumps, dump checkpoints
itself at the start of each tape volume. If writing that volume fails for some reason,
dump will, with operator permission, restart itself from the checkpoint after the old tape
has been rewound and removed, and a new tape has been mounted.
Dump tells the operator what is going on at periodic intervals, including usually low
estimates of the number of blocks to write, the number of tapes it will take, the time to
completion, and the time to the tape change. The output is verbose, so that others know
that the terminal controlling dump is busy, and will be for some time.
In the event of a catastrophic disk event, the time required to restore all the necessary
backup tapes or files to disk can be kept to a minimum by staggering the incremental
dumps. An efficient method of staggering incremental dumps to minimize the number of tapes
follows:
— Always start with a level 0 backup, for example:
/sbin/dump -0u -f /dev/st0 /usr/src
This should be done at set intervals, say once a month or once every two months,
and on a set of fresh tapes that is saved forever.
— After a level 0, dumps of active file systems are taken on a daily basis, with this
sequence of dump levels:
3 2 5 4 7 6 9 8 9 9 ...
For the daily dumps, it should be possible to use a fixed number of tapes for each
day, used on a weekly basis. Each week, a level 1 dump is taken, and the daily
Hanoi sequence repeats beginning with 3. For weekly dumps, another fixed set of
tapes per dumped file system is used, also on a cyclical basis.
After several months or so, the daily and weekly tapes should get rotated out of the dump
cycle and fresh tapes brought in.
Another backup strategy is the Tower of Hanoi sequence, which reuses older tapes in a way
that for newer dates the available restore points are more frequent, then for older dates
(see https://en.wikipedia.org/wiki/Backup_rotation_scheme for additional information).
(The 4.3BSD option syntax is implemented for backward compatibility but is not documented
here.)
ENVIRONMENT
TAPE If no -f option was specified, dump will use the device specified via TAPE as the
dump device. TAPE may be of the form tapename, host:tapename, or
user@host:tapename.
RMT The environment variable RMT will be used to determine the pathname of the remote
rmt(8) program.
RSH Dump uses the contents of this variable to determine the name of the remote shell
command to use when doing remote backups (rsh, ssh etc.). If this variable is not
set, rcmd(3) will be used, but only root will be able to do remote backups.
FILES
/dev/st0
default tape unit to dump to
/var/lib/dumpdates
dump date records
/etc/fstab
dump table: file systems and frequency
/etc/mtab
dump table: mounted file systems
/etc/group
to find group operator
SEE ALSO
fstab(5), restore(8), rmt(8)
DIAGNOSTICS
Many, and verbose.
COMPATIBILITY
The format of the /var/lib/dumpdates file has changed in release 0.4b34, however, the file
will be read correctly with either pre-0.4b34 or 0.4b34 and later versions of dump
provided that the machine on which dump is run did not change timezones (which should be a
fairly rare occurrence).
EXIT STATUS
Dump exits with zero status on success. Startup errors are indicated with an exit code of
1; abnormal termination is indicated with an exit code of 3.
BUGS
It might be considered a bug that this version of dump can only handle ext2/3/4
filesystems. Specifically, it does not work with FAT filesystems.
Fewer than 32 read errors (change this with -I) on the filesystem are ignored. If noticing
read errors is important, the output from dump can be parsed to look for lines that
contain the text 'read error'.
When a read error occurs, dump prints out the corresponding physical disk block and sector
number and the ext2/3/4 logical block number. It doesn't print out the corresponding file
name or even the inode number. The user has to use debugfs(8), commands ncheck and icheck
to translate the ext2blk number printed out by dump into an inode number, then into a file
name.
Each reel requires a new process, so parent processes for reels already written just hang
around until the entire tape is written.
The estimated number of tapes is not correct if compression is on.
It would be nice if dump knew about the dump sequence, kept track of the tapes scribbled
on, told the operator which tape to mount when, and provided more assistance for the
operator running restore.
Dump cannot do remote backups without being run as root, due to its security history.
Presently, it works if you set it setuid (like it used to be), but this might constitute a
security risk. Note that you can set RSH to use a remote shell program instead.
AUTHOR
The dump/restore backup suite was ported to Linux's Second Extended File System by Remy
Card <card@Linux.EU.Org>. He maintained the initial versions of dump (up and including
0.4b4, released in January 1997).
Starting with 0.4b5, the new maintainer is Stelian Pop <stelian@popies.net>.
AVAILABILITY
The dump/restore backup suite is available from <https://dump.sourceforge.io>
HISTORY
A dump command appeared in Version 6 AT&T UNIX.