mirror of
git://sourceware.org/git/lvm2.git
synced 2024-12-21 13:34:40 +03:00
130 lines
4.2 KiB
Plaintext
130 lines
4.2 KiB
Plaintext
.TH LVMETAD 8 "LVM TOOLS #VERSION#" "Red Hat Inc" \" -*- nroff -*-
|
|
.SH NAME
|
|
lvmetad \(em LVM metadata cache daemon
|
|
|
|
.SH SYNOPSIS
|
|
.B lvmetad
|
|
.RB [ -l
|
|
.IR level [,level...]]
|
|
.RB [ -p
|
|
.IR pidfile_path ]
|
|
.RB [ -s
|
|
.IR socket_path ]
|
|
.RB [ -t
|
|
.IR timeout_value ]
|
|
.RB [ -f ]
|
|
.RB [ -h ]
|
|
.RB [ -V ]
|
|
.RB [ -? ]
|
|
|
|
.SH 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
|
|
.BR 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:
|
|
.br
|
|
.BR lvm.conf (5)
|
|
.B global/use_lvmetad
|
|
|
|
For more information on this setting, see:
|
|
.br
|
|
.B lvmconfig --withcomments global/use_lvmetad
|
|
|
|
To ignore disks from LVM at the system level, e.g. lvmetad, pvscan use:
|
|
.br
|
|
.BR lvm.conf (5)
|
|
.B devices/global_filter
|
|
|
|
For more information on this setting, see
|
|
.br
|
|
.B lvmconfig --withcomments devices/global_filter
|
|
|
|
.SH OPTIONS
|
|
|
|
To run the daemon in a test environment both the pidfile_path and the
|
|
socket_path should be changed from the defaults.
|
|
.TP
|
|
.B -f
|
|
Don't fork, but run in the foreground.
|
|
.TP
|
|
.BR -h ", " -?
|
|
Show help information.
|
|
.TP
|
|
.B -l \fIlevels
|
|
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.
|
|
.TP
|
|
.B -p \fIpidfile_path
|
|
Path to the pidfile. This overrides both the built-in default
|
|
(#DEFAULT_PID_DIR#/lvmetad.pid) and the environment variable
|
|
\fBLVM_LVMETAD_PIDFILE\fP. This file is used to prevent more
|
|
than one instance of the daemon running simultaneously.
|
|
.TP
|
|
.B -s \fIsocket_path
|
|
Path to the socket file. This overrides both the built-in default
|
|
(#DEFAULT_RUN_DIR#/lvmetad.socket) and the environment variable
|
|
\fBLVM_LVMETAD_SOCKET\fP. To communicate successfully with lvmetad,
|
|
all LVM2 processes should use the same socket path.
|
|
.TP
|
|
.B -t \fItimeout_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.
|
|
.TP
|
|
.B -V
|
|
Display the version of lvmetad daemon.
|
|
.SH ENVIRONMENT VARIABLES
|
|
.TP
|
|
.B LVM_LVMETAD_PIDFILE
|
|
Path for the pid file.
|
|
.TP
|
|
.B LVM_LVMETAD_SOCKET
|
|
Path for the socket file.
|
|
|
|
.SH SEE ALSO
|
|
.BR lvm (8),
|
|
.BR lvmconfig (8),
|
|
.BR lvm.conf (5),
|
|
.BR pvscan (8)
|