diff options
Diffstat (limited to 'man/pvscan.8_pregen')
| -rw-r--r-- | man/pvscan.8_pregen | 111 |
1 files changed, 35 insertions, 76 deletions
diff --git a/man/pvscan.8_pregen b/man/pvscan.8_pregen index 2326ec55e..ed5ba9241 100644 --- a/man/pvscan.8_pregen +++ b/man/pvscan.8_pregen @@ -10,73 +10,50 @@ pvscan - List all physical volumes [ \fIposition_args\fP ] .br .SH DESCRIPTION -pvscan scans all supported LVM block devices in the system for PVs. +When called without the --cache option, pvscan lists PVs on the system, +like +.BR pvs (8) +or +.BR pvdisplay (8). + +When the --cache and -aay options are used, pvscan records which PVs are +available on the system, and activates LVs in completed VGs. A VG is +complete when pvscan sees that the final PV in the VG has appeared. This +is used by event-based system startup (systemd, udev) to activate LVs. + +The four main variations of this are: + +.B pvscan --cache +.IR device -\fBScanning with lvmetad\fP +If device is present, lvm adds a record that the PV on device is online. +If device is not present, lvm removes the online record for the PV. +In most cases, the pvscan will only read the named devices. -pvscan operates differently when used with the -.BR lvmetad (8) -daemon. +.B pvscan --cache -aay +.IR device ... -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. +This begins by performing the same steps as above. Afterward, if the VG +for the specified PV is complete, then pvscan will activate LVs in the VG +(the same as vgchange -aay vgname would do.) -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. +.B pvscan --cache -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. +This first clears all existing PV online records, then scans all devices +on the system, adding PV online records for any PVs that are found. -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. +.B pvscan --cache -aay + +This begins by performing the same steps as pvscan --cache. Afterward, it +activates LVs in any complete VGs. -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 @@ -87,21 +64,12 @@ 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.) +To disable auto-activation, explicitly set this list to an empty list, +i.e. auto_activation_volume_list = [ ]. + +When this setting is undefined (e.g. commented), then all LVs are +auto-activated. -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. .SH USAGE Display PV information. .br @@ -136,10 +104,6 @@ Autoactivate a VG when all PVs are online. .br .RS 4 .ad l -[ \fB-b\fP|\fB--background\fP ] -.ad b -.br -.ad l [ \fB-a\fP|\fB--activate\fP \fBay\fP ] .ad b .br @@ -239,9 +203,6 @@ Auto-activate LVs in a VG when the PVs scanned have completed the VG. .ad b .HP .ad l -\fB-b\fP|\fB--background\fP.ad b -.HP -.ad l \fB--cache\fP .br Scan one or more devices and record that they are online. @@ -486,11 +447,9 @@ For example, LVM_VG_NAME can generally be substituted for a required VG paramete .BR lvmdump (8) .BR dmeventd (8) -.BR lvmetad (8) .BR lvmpolld (8) .BR lvmlockd (8) .BR lvmlockctl (8) -.BR clvmd (8) .BR cmirrord (8) .BR lvmdbusd (8) |