NAME

       lvmetad — LVM metadata cache daemon

SYNOPSIS

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

DESCRIPTION

       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

       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  (/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
              (/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

       LVM_LVMETAD_PIDFILE
              Path for the pid file.

       LVM_LVMETAD_SOCKET
              Path for the socket file.

SEE ALSO

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