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CNID_DBD(8) Netatalk AFP Fileserver Manual CNID_DBD(8) Name cnid_dbd -- CNID database access daemon Synopsis cnid_dbd 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 when using the dbd (Database Daemon) CNID backend. CNIDs are a component of Classic Mac OS based file systems with semantics that does not map easily onto Unix file systems. This makes separate stor- age in a database necessary. 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 Berkeley 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 Berkeley 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 inher- ited 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 can be configured to run forever or to exit after a period of in- activity. If cnid_dbd receives a TERM or an INT signal it will exit cleanly after flushing dirty database buffers to disk and closing Berkeley DB data- base 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 Berkeley 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 the transactional database changes. They will be removed regularly, unless the logfile_autoremove option is specified in the db_param configuration file (see below) with a value of 0 (default 1). 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 para- meter 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 para- meters 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 regular 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 perfor- mance. The db_stat utility with the -m option that comes with Berke- ley DB can help you determine whether you need to change this value. The default is pretty conservative so that a large percentage of re- quests 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_fre- quency requests have been received or ii) more than flush_interval seconds have elapsed since the last save/checkpoint. Be careful to check your hard disk configuration for on disk cache settings. Many IDE disks just cache writes as the default behaviour, so even flush- ing 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 ex- its. Default: 600. Set this to 0 to disable the timeout. Updating Starting with Netatalk 2.1.1, automatic Berkeley DB updates are supported, as long as Netatalk 2.1.0 or later was used to create the database. In order to update between older Netatalk releases using different Berkeley DB library versions, follow these steps: * Stop the to be upgraded old version of Netatalk * Using the old Berkeley DB utilities run db_recover -h path/to/.AppleDB * Using the new Berkeley DB utilities run db_upgrade -v -h path/to/.AppleDB -f cnid2.db * Again using the new Berkeley DB utilities run db_checkpoint -1 -h path/to/.AppleDB * Start the the new version of Netatalk Wire Protocol cnid_dbd speaks a private TCP/IP protocol with afpd and nad on local- host:4700 (configurable per-volume via cnid server / cnid port in afp.conf(5)). The protocol is internal and may change between releases. Af- ter a netatalk upgrade, restart the netatalk service. See Also cnid_metad(8), afpd(8), dbd(1) Author Contributors to the Netatalk Project (https://netatalk.io/contributors) Netatalk 4.5.0 CNID_DBD(8)
Name | Synopsis | Description | Options | Configuration | Updating | Wire Protocol | See Also | Author
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