mirror of
git://sourceware.org/git/lvm2.git
synced 2024-12-23 21:35:29 +03:00
200793edc6
rather than -a|--activate, because web pages on man7.org are not printing the | character.
93 lines
3.7 KiB
Plaintext
93 lines
3.7 KiB
Plaintext
pvscan scans all supported LVM block devices in the system for PVs.
|
|
|
|
\fBScanning with lvmetad\fP
|
|
|
|
pvscan operates differently when used with the
|
|
.BR lvmetad (8)
|
|
daemon.
|
|
|
|
Scanning disks is required to read LVM metadata and identify LVM PVs.
|
|
Once read, lvmetad caches the metadata so that LVM commands can read it
|
|
without repeatedly scanning disks. This is helpful because scanning disks
|
|
is time consuming, and frequent scanning may interfere with the normal
|
|
work of the system and disks.
|
|
|
|
When lvmetad is not used, LVM commands revert to scanning disks to read
|
|
metadata. Any LVM command that needs metadata will scan disks for it;
|
|
running the pvscan command is not necessary for the sake of other LVM
|
|
commands.
|
|
|
|
When lvmetad is used, LVM commands avoid scanning disks by reading
|
|
metadata from lvmetad. When new disks appear, they must be scanned so
|
|
their metadata can be cached in lvmetad. This is done by the command
|
|
pvscan --cache, which scans disks and passes the metadata to lvmetad.
|
|
|
|
The pvscan --cache command is typically run automatically by system
|
|
services when a new device appears. Users do not generally need to run
|
|
this command if the system and lvmetad are running properly.
|
|
|
|
Many scripts contain unnecessary pvscan (or vgscan) commands for
|
|
historical reasons. To avoid disrupting the system with extraneous disk
|
|
scanning, an ordinary pvscan (without --cache) will simply read metadata
|
|
from lvmetad like other LVM commands. It does not do anything beyond
|
|
displaying the current state of the cache.
|
|
.IP \[bu] 2
|
|
When given specific device name arguments, pvscan --cache will only
|
|
read the named devices.
|
|
.IP \[bu] 2
|
|
LVM udev rules and systemd services are used to initiate automatic device
|
|
scanning.
|
|
.IP \[bu] 2
|
|
To prevent devices from being scanned by pvscan --cache, add them
|
|
to
|
|
.BR lvm.conf (5)
|
|
.B devices/global_filter.
|
|
The devices/filter setting does not
|
|
apply to system level scanning.
|
|
For more information, see:
|
|
.br
|
|
.B lvmconfig --withcomments devices/global_filter
|
|
.IP \[bu] 2
|
|
If lvmetad is started or restarted after devices are visible, or
|
|
if the global_filter has changed, then all devices must be rescanned
|
|
for metadata with the command pvscan --cache.
|
|
.IP \[bu] 2
|
|
lvmetad does not cache older metadata formats, e.g. lvm1, and will
|
|
be temporarily disabled if they are seen.
|
|
.IP \[bu] 2
|
|
To notify lvmetad about a device that is no longer present, the major and
|
|
minor numbers must be given, not the path.
|
|
.P
|
|
\fBAutomatic activation\fP
|
|
|
|
When event-driven system services detect a new LVM device, the first step
|
|
is to automatically scan and cache the metadata from the device. This is
|
|
done by pvscan --cache. A second step is to automatically activate LVs
|
|
that are present on the new device. This auto-activation is done by the
|
|
same pvscan --cache command when the option --activate ay is included.
|
|
|
|
Auto-activation of VGs or LVs can be enabled/disabled using:
|
|
.br
|
|
.BR lvm.conf (5)
|
|
.B activation/auto_activation_volume_list
|
|
|
|
For more information, see:
|
|
.br
|
|
.B lvmconfig --withcomments activation/auto_activation_volume_list
|
|
|
|
When this setting is undefined, all LVs are auto-activated (when lvm is
|
|
fully integrated with the event-driven system services.)
|
|
|
|
When a VG or LV is not auto-activated, traditional activation using
|
|
vgchange or lvchange --activate is needed.
|
|
.IP \[bu] 2
|
|
pvscan auto-activation can be only done in combination with --cache.
|
|
.IP \[bu] 2
|
|
Auto-activation is designated by the "a" argument in --activate ay.
|
|
This is meant to distinguish system generated commands from explicit user
|
|
commands, although it can be used in any activation command. Whenever it
|
|
is used, the auto_activation_volume_list is applied.
|
|
.IP \[bu] 2
|
|
Auto-activation is not yet supported for LVs that are part of partial or
|
|
clustered volume groups.
|