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| -rw-r--r-- | man/lvmetad.8.in | 63 |
1 files changed, 53 insertions, 10 deletions
diff --git a/man/lvmetad.8.in b/man/lvmetad.8.in index 3ea80c971..cdaf198ca 100644 --- a/man/lvmetad.8.in +++ b/man/lvmetad.8.in @@ -1,6 +1,7 @@ .TH LVMETAD 8 "LVM TOOLS #VERSION#" "Red Hat Inc" \" -*- nroff -*- .SH NAME lvmetad \(em LVM metadata cache daemon + .SH SYNOPSIS .B lvmetad .RB [ \-l @@ -13,16 +14,56 @@ lvmetad \(em LVM metadata cache daemon .RB [ \-h ] .RB [ \-V ] .RB [ \-? ] + .SH DESCRIPTION -lvmetad is a metadata caching daemon for LVM. The daemon receives notifications -from udev rules (which must be installed for LVM to work correctly when lvmetad -is in use). Through these notifications, lvmetad has an up-to-date and -consistent image of the volume groups available in the system. - -lvmetad is used by LVM only if it is enabled in \fBlvm.conf\fP(5) by specifying the -\fBglobal/use_lvmetad\fP setting. If this is not defined in the LVM configuration -explicitly then default setting is used instead (see the output of -\fBlvmconfig \-\-type default global/use_lvmetad\fP command). + +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 +.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 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: +.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 @@ -68,4 +109,6 @@ Path for the socket file. .SH SEE ALSO .BR lvm (8), -.BR lvm.conf (5) +.BR lvmconfig (8), +.BR lvm.conf (5), +.BR pvscan (8) |