Provided by: netatalk_2.2.5-1_amd64 bug

NAME

       cnid_dbd - implement access to CNID databases through a dedicated daemon process

SYNOPSIS

       cnid_dbd volpath ctrlfd clntfd logconfig_string
                        cnid_dbd -v | -V

DESCRIPTION

       cnid_dbd provides an interface for storage and retrieval of catalog node IDs (CNIDs) and
       related information to the afpd daemon. CNIDs are a component of Macintosh based file
       systems with semantics that map not easily onto Unix file systems. This makes separate
       storage in a database necessary.  cnid_dbd is part of the CNID backend framework of afpd
       and implements the dbd backend.

       cnid_dbd is never started via the command line or system startup scripts but only by the
       cnid_metad daemon. There is one instance of cnid_dbd per netatalk volume.

       cnid_dbd uses the Berkleley DB database library and uses transactionally protected
       updates. The dbd backend with transactions will avoid corruption of the CNID database even
       if the system crashes unexpectedly.

       cnid_dbd inherits the effective userid and groupid from cnid_metad on startup, which is
       normally caused by afpd serving a netatalk volume to a client. It changes to the Berkleley
       DB database home directory dbdir that is associated with the volume. If the userid
       inherited from cnid_metad is 0 (root), cnid_dbd will change userid and groupid to the
       owner and group of the database home directory. Otherwise, it will continue to use the
       inherited values.  cnid_dbd will then attempt to open the database and start serving
       requests using filedescriptor clntfd. Subsequent instances of afpd that want to access the
       same volume are redirected to the running cnid_dbd process by cnid_metad via the
       filedescriptor ctrlfd.

       cnid_dbd uses logconfig_string which is passed from cnid_metad to configure its logging
       output.

       cnid_dbd can be configured to run forever or to exit after a period of inactivity. If
       cnid_dbd receives a TERM or an INT signal it will exit cleanly after flushing dirty
       database buffers to disk and closing Berkleley DB database environments. It is safe to
       terminate cnid_dbd this way, it will be restarted when necessary. Other signals are not
       handled and will cause an immediate exit, possibly leaving the CNID database in an
       inconsistent state (no transactions) or losing recent updates during recovery
       (transactions).

       The Berkleley DB database subsystem will create files named log.xxxxxxxxxx in the database
       home directory dbdir, where xxxxxxxxxx is a monotonically increasing integer. These files
       contain ithe transactional database changes. They will be removed regularily, unless the
       logfile_autoremove option is specified in the db_param configuration file (see below) with
       a value of 0 (default 1).

       Do not use cnid_dbd for databases on NFS mounted file systems. It makes the whole point of
       securing database changes properly moot. Use the dbdir: Option in the appropriate
       AppleVolumes configuration file to put the database onto a local disk.

OPTIONS

       -v, -V
           Show version and exit.

CONFIGURATION

       cnid_dbd reads configuration information from the file db_param in the database directory
       dbdir on startup. If the file does not exist or a parameter is not listed, suitable
       default values are used. The format for a single parameter is the parameter name, followed
       by one or more spaces, followed by the parameter value, followed by a newline. The
       following parameters are currently recognized:

       logfile_autoremove
           If set to 0, unused Berkeley DB transactional logfiles (log.xxxxxxxxxx in the database
           home directory) are not removed on startup of cnid_dbd and on a reqular basis.
           Default: 1.

       cachesize
           Determines the size of the Berkeley DB cache in kilobytes. Default: 8192. Each
           cnid_dbd process grabs that much memory on top of its normal memory footprint. It can
           be used to tune database performance. The db_stat utility with the -m option that
           comes with Berkely DB can help you determine wether you need to change this value. The
           default is pretty conservative so that a large percentage of requests should be
           satisfied from the cache directly. If memory is not a bottleneck on your system you
           might want to leave it at that value. The Berkeley DB Tutorial and Reference Guide has
           a section Selecting a cache size that gives more detailed information.

       flush_frequency, flush_interval
           flush_frequency (Default: 1000) and flush_interval (Default: 1800) control how often
           changes to the database are checkpointed. Both of these operations are performed if
           either i) more than flush_frequency requests have been received or ii) more than
           flush_interval seconds have elapsed since the last save/checkpoint. Be careful to
           check your harddisk configuration for on disk cache settings. Many IDE disks just
           cache writes as the default behaviour, so even flushing database files to disk will
           not have the desired effect.

       fd_table_size
           is the maximum number of connections (filedescriptors) that can be open for afpd
           client processes in cnid_dbd.  Default: 512. If this number is exceeded, one of the
           existing connections is closed and reused. The affected afpd process will
           transparently reconnect later, which causes slight overhead. On the other hand,
           setting this parameter too high could affect performance in cnid_dbd since all
           descriptors have to be checked in a select() system call, or worse, you might exceed
           the per process limit of open file descriptors on your system. It is safe to set the
           value to 1 on volumes where only one afpd client process is expected to run, e.g. home
           directories.

       idle_timeout
           is the number of seconds of inactivity before an idle cnid_dbd exits. Default: 600.
           Set this to 0 to disable the timeout.

UPDATING

       Note that the first version to appear after Netatalk 2.1 i.e. Netatalk 2.1.1, will support
       BerkeleyDB updates on the fly without manual intervention. In other words Netatalk 2.1
       does contain code to prepare the BerkeleyDB database for upgrades and to upgrade it in
       case it has been prepared before. That means it can´t upgrade a 2.0.x version because that
       one didn´t prepare the database.

       In order to update between older Netatalk releases using different BerkeleyDB library
       versions, follow this steps:

       ·   Stop the to be upgraded old version of Netatalk

       ·   Using the old BerkeleyDB utilities run db_recover -h <path to .AppleDB>

       ·   Using the new BerkeleyDB utilities run db_upgrade -v -h <path to .AppleDB> -f cnid2.db

       ·   Again using the new BerkeleyDB utilities run db_checkpoint -1 -h <path to .AppleDB>

       ·   Start the the new version of Netatalk

SEE ALSO

       cnid_metad(8), afpd(8), dbd(1)