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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT VARIABLES | SEE ALSO | COLOPHON |
LVMETAD(8) System Manager's Manual LVMETAD(8)
lvmetad — LVM metadata cache daemon
lvmetad [-l level[,level...]] [-p pidfile_path] [-s socket_path] [-t
timeout_value] [-f] [-h] [-V] [-?]
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
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.
LVM_LVMETAD_PIDFILE
Path for the pid file.
LVM_LVMETAD_SOCKET
Path for the socket file.
lvm(8), lvmconfig(8), lvm.conf(5), pvscan(8)
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)
Pages that refer to this page: lvchange(8), lvconvert(8), lvcreate(8), lvdisplay(8), lvextend(8), lvm2-activation-generator(8), lvm(8), lvmconfig(8), lvmdiskscan(8), lvmdump(8), lvm-fullreport(8), lvm-lvpoll(8), lvreduce(8), lvremove(8), lvrename(8), lvresize(8), lvs(8), lvscan(8), pvchange(8), pvck(8), pvcreate(8), pvdisplay(8), pvmove(8), pvremove(8), pvresize(8), pvs(8), pvscan(8), vgcfgbackup(8), vgcfgrestore(8), vgchange(8), vgck(8), vgconvert(8), vgcreate(8), vgdisplay(8), vgexport(8), vgextend(8), vgimport(8), vgimportclone(8), vgmerge(8), vgmknodes(8), vgreduce(8), vgremove(8), vgrename(8), vgs(8), vgscan(8), vgsplit(8)