NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT VARIABLES | SEE ALSO | COLOPHON

LVMETAD(8)                 System Manager's Manual                LVMETAD(8)

NAME         top

       lvmetad — LVM metadata cache daemon

SYNOPSIS         top

       lvmetad [-l level[,level...]]  [-p pidfile_path] [-s socket_path] [-t
       timeout_value] [-f] [-h] [-V] [-?]

DESCRIPTION         top

       The lvmetad daemon caches LVM metadata so that LVM commands can read
       metadata from the cache rather than scanning disks.  This can be an
       advantage because scanning disks is time consuming and may interfere
       with the normal work of the system.  lvmetad can be a disadvantage
       when disk event notifications from the system are unreliable.

       lvmetad does not read metadata from disks itself.  Instead, it relies
       on an LVM command, like pvscan --cache, to read metadata from disks
       and send it to lvmetad to be cached.

       New LVM disks that appear on the system must be scanned before
       lvmetad knows about them.  If lvmetad does not know about a disk,
       then LVM commands using lvmetad will also not know about it.  When
       disks are added or removed from the system, lvmetad must be updated.

       lvmetad is usually combined with event-based system services that
       automatically run pvscan --cache on disks added or removed.  This
       way, the cache is automatically updated with metadata from new disks
       when they appear.  LVM udev rules and systemd services implement this
       automation.  Automatic scanning is usually combined with automatic
       activation.  For more information, see pvscan(8).

       If lvmetad is started or restarted after disks have been added to the
       system, or if the global_filter has changed, the cache must be
       updated.  This can be done by running pvscan --cache, or it will be
       done automatically by the next LVM command that's run.

       When lvmetad is not used, LVM commands revert to scanning disks for
       LVM metadata.

       In some cases, lvmetad will be temporarily disabled while it
       continues running.  In this state, LVM commands will ignore the
       lvmetad cache and revert to scanning disks.  A warning will also be
       printed which includes the reason why lvmetad is not being used.  The
       most common reasons are the existence of duplicate PVs (lvmetad
       cannot cache data for duplicate PVs), or an 'lvconvert --repair'
       command has been run (the lvmetad cache may not be reliable while
       repairs are neeeded.)  Once duplicates have been resolved, or repairs
       have been completed, the lvmetad cache is can be updated with pvscan
       --cache and commands will return to using the cache.

       Use of lvmetad is enabled/disabled by:
       lvm.conf(5) global/use_lvmetad

       For more information on this setting, see:
       lvmconfig --withcomments global/use_lvmetad

       To ignore disks from LVM at the system level, e.g. lvmetad, pvscan
       use:
       lvm.conf(5) devices/global_filter

       For more information on this setting, see
       lvmconfig --withcomments devices/global_filter

OPTIONS         top

       To run the daemon in a test environment both the pidfile_path and the
       socket_path should be changed from the defaults.

       -f     Don't fork, but run in the foreground.

       -h, -? Show help information.

       -l levels
              Specify the levels of log messages to generate as a comma
              separated list.  Messages are logged by syslog.  Additionally,
              when -f is given they are also sent to standard error.
              Possible levels are: all, fatal, error, warn, info, wire,
              debug.

       -p pidfile_path
              Path to the pidfile. This overrides both the built-in default
              (/var/run/lvmetad.pid) and the environment variable
              LVM_LVMETAD_PIDFILE.  This file is used to prevent more than
              one instance of the daemon running simultaneously.

       -s socket_path
              Path to the socket file. This overrides both the built-in
              default (/var/run/lvm/lvmetad.socket) and the environment
              variable LVM_LVMETAD_SOCKET.  To communicate successfully with
              lvmetad, all LVM2 processes should use the same socket path.

       -t timeout_value
              The daemon may shutdown after being idle for the given time
              (in seconds). When the option is omitted or the value given is
              zero the daemon never shutdowns on idle.

       -V     Display the version of lvmetad daemon.

ENVIRONMENT VARIABLES         top

       LVM_LVMETAD_PIDFILE
              Path for the pid file.

       LVM_LVMETAD_SOCKET
              Path for the socket file.

SEE ALSO         top

       lvm(8), lvmconfig(8), lvm.conf(5), pvscan(8)

COLOPHON         top

       This page is part of the lvm2 (Logical Volume Manager 2) project.
       Information about the project can be found at 
       ⟨http://www.sourceware.org/lvm2/⟩.  If you have a bug report for this
       manual page, send it to linux-lvm@redhat.com.  This page was obtained
       from the project's upstream Git repository 
       ⟨git://sourceware.org/git/lvm2.git⟩ on 2017-07-05.  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

Red Hat Inc        LVM TOOLS 2.02.173(2)-git (2017-06-28)         LVMETAD(8)

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