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 without scanning disks.

       Metadata  caching can be an advantage because scanning disks is time consuming and may interfere with the
       normal work of the system and disks.

       lvmetad does not read metadata from disks itself.  The 'pvscan --cache' command scans  disks,  reads  the
       LVM metadata and sends it to lvmetad.

       New  LVM  disks  that appear on the system must be scanned by pvscan 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 new
       disks.  This way, the lvmetad 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 by running 'pvscan --cache'.

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

       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)