lvmautoactivation(7) — Linux manual page

NAME | DESCRIPTION | EXAMPLES | COLOPHON

LVMAUTOACTIVATION(7)                                LVMAUTOACTIVATION(7)

NAME         top

       lvmautoactivation — LVM autoactivation

DESCRIPTION         top

       Autoactivation is the activation of LVs performed automatically
       by the system in response to LVM devices being attached to the
       machine.  When all PVs in a VG have been attached, the VG is
       complete, and LVs in the VG are activated.

       Autoactivation of VGs, or specific LVs, can be prevented using
       vgchange or lvchange --setautoactivation n.  The lvm.conf
       auto_activation_volume_list is another way to limit
       autoactivation.

   event autoactivation
       LVM autoactivation is "event based", in which complete VGs are
       activated in response to uevents which occur during system
       startup or at any time after the system has started.  An old form
       of autoactivation was "static" in which complete VGs are
       activated at a fixed point during system startup by a systemd
       service, and not in response to events.

       Event based autoactivation is driven by udev, udev rules, and
       systemd.  When a device is attached to a machine, a uevent is
       generated by the kernel to notify userspace of the new device.
       systemd-udev runs udev rules to process the new device.  Udev
       rules use blkid to identify the device as an LVM PV and then
       execute the lvm-specific udev rule for the device, which triggers
       autoactivation.

       There are two variations of event based autoactivation that may
       be used on a system, depending on the LVM udev rule that is
       installed (found in /lib/udev/rules.d/.)  The following
       summarizes the steps in each rule which lead to autoactivation:

       69-dm-lvm-metad.rules

       • device /dev/name with major:minor X:Y is attached to the
         machine

       • systemd/udev runs blkid to identify /dev/name as an LVM PV

       • udev rule 69-dm-lvm-metad.rules is run for /dev/name

       • the lvm udev rule runs the systemd service
         lvm2-pvscan@X:Yservice

       • the lvm2-pvscan service runs:
         pvscan --cache -aay --major X --minor Y

       • pvscan reads the device, records that the PV is online (see
         pvs_online), and checks if the VG is complete.

       • if the VG is complete, pvscan creates the vgs_online temp file,
         and activates the VG.

       • the activation command output can be seen from systemctl status
         lvm2-pvscan*

       69-dm-lvm.rules

       • device /dev/name with major:minor X:Y is attached to the
         machine

       • systemd/udev runs blkid to identify /dev/name as an LVM PV

       • udev rule 69-dm-lvm.rules is run for /dev/name

       • the lvm udev rule runs:
         pvscan --cache --listvg --checkcomplete --vgonline
         --autoactivation event --udevoutput --journal=output /dev/name

       • pvscan reads the device, records that the PV is online (see
         pvs_online), and checks if the VG is complete.

       • if the VG is complete, pvscan creates the vgs_online temp file,
         and prints the name of the VG for the udev rule to import:
         LVM_VG_NAME_COMPLETE='vgname'

       • if the lvm udev rule sees LVM_VG_NAME_COMPLETE from pvscan, it
         activates the VG using a transient systemd service named lvm-
         activate-<vgname>.

       • the lvm-activate-<vgname> service runs
         vgchange -aay --autoactivation event <vgname>

       • the activation command output can be seen from journalctl -u
         lvm-activate-<vgname>

   pvscan options
       --cache
       Read the <device> arg (and only that device), and record that the
       PV is online by creating the /run/lvm/pvs_online/<pvid> file
       containing the name of the VG and the device for the PV.

       -aay
       Activate the VG from the pvscan command (includes implicit
       --checkcomplete and --vgonline.)

       --checkcomplete
       Check if the VG is complete, i.e. all PVs are present on the
       system, by checking /run/lvm/pvs_online/<pvid> files.

       --vgonline
       Create /run/lvm/vgs_online/<vgname> if the VG is complete (used
       to ensure only one command performs activation.)

       --autoactivation event
       Inform the command it is used for event based autoactivation.

       --listvg
       Print the name of the VG using the device.

       --udevoutput
       Only print output that can be imported to the udev rule, using
       the udev environment key format, i.e. NAME='value'.

       --journal=output
       Send standard command output to the journal (when stdout is
       reserved for udev output.)

   run files
       Autoactivation commands use a number of temp files in /run/lvm
       (with the expectation that /run is cleared between boots.)

       pvs_online
       pvscan --cache creates a file here for each PV that is attached.
       The file is named with the PVID and contains the VG name and
       device information.  The existence of the file is used to
       determine when all PVs for a given VG are present.  The device
       information in these files is also used to optimize locating
       devices for a VG when the VG is activated.

       pvs_lookup
       pvscan --cache creates a file here named for a VG (if one doesn't
       already exist.)  The file contains a list of PVIDs in the VG.
       This is needed when a PV is processed which has no VG metadata,
       in which case the list of PVIDs from the lookup file is used to
       check if the VG is complete.

       vgs_online
       The first activation command (pvscan or vgchange) to create a
       file here, named for the VG, will activate the VG.  This resolves
       a race when concurrent commands attempt to activate a VG at once.

   static autoactivation
       A static autoactivation method is no longer provided by lvm.
       Setting event_activation=0 still disables event based
       autoactivation.  WARNING: disabling event activation without an
       alternative may prevent a system from booting.  A custom systemd
       service could be written to run autoactivation during system
       startup, in which case disabling event autoactivation may be
       useful.

   lvm.conf filter
       Device symlinks from /dev/disk/ can be used in the lvm.conf
       filter to guard against changes in kernel device names. The
       /dev/disk/by-path/ or /dev/disk/by-id/ prefixes should be
       included in the filter names; these prefixes help lvm detect that
       symlink names are used. Filters containing symlinks require
       special matching by commands run in the lvm udev rule.

       Common symlinks, e.g. beginning with wwn-, scsi-, pci-, or lvm-
       pv-uuid-, are recommended.  Uncommon or custom symlinks created
       by custom udev rules may be less reliable. If a custom udev rule
       creates symlinks used in the lvm filter, then the udev rule
       should be started prior to the lvm rule.

EXAMPLES         top

       VG "vg" contains two PVs:
       $ pvs -o name,vgname,uuid /dev/sdb /dev/sdc
         PV         VG PV UUID
         /dev/sdb   vg 1uKpaT-lFOZ-NLHX-j4jI-OBi1-QpdE-HZ5hZY
         /dev/sdc   vg 5J3tM8-aIPe-2vbd-DBe7-bvRq-TGj0-DaKV2G

       use of --cache:
       $ pvscan --cache /dev/sdb
         pvscan[12922] PV /dev/sdb online.
       $ pvscan --cache /dev/sdc
         pvscan[12923] PV /dev/sdc online.

       $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
       8:16
       vg:vg
       dev:/dev/sdb
       $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
       8:32
       vg:vg
       dev:/dev/sdc

       use of -aay:
       $ pvscan --cache -aay /dev/sdb
         pvscan[12935] PV /dev/sdb online, VG vg incomplete (need 1).
       $ pvscan --cache -aay /dev/sdc
         pvscan[12936] PV /dev/sdc online, VG vg is complete.
         pvscan[12936] VG vg run autoactivation.
         1 logical volume(s) in volume group "vg" now active

       $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
       8:16
       vg:vg
       dev:/dev/sdb
       $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
       8:32
       vg:vg
       dev:/dev/sdc
       $ ls /run/lvm/vgs_online/vg
       /run/lvm/vgs_online/vg

       use of --listvg:
       $ pvscan --cache --listvg /dev/sdb
         VG vg
       $ pvscan --cache --listvg /dev/sdc
         VG vg

       $ cat /run/lvm/pvs_online/1uKpaTlFOZNLHXj4jIOBi1QpdEHZ5hZY
       8:16
       vg:vg
       dev:/dev/sdb
       $ cat /run/lvm/pvs_online/5J3tM8aIPe2vbdDBe7bvRqTGj0DaKV2G
       8:32
       vg:vg
       dev:/dev/sdc

       use of --checkcomplete:
       $ pvscan --cache --listvg --checkcomplete --vgonline /dev/sdb
         pvscan[12996] PV /dev/sdb online, VG vg incomplete (need 1).
         VG vg incomplete
       $ pvscan --cache --listvg --checkcomplete --vgonline /dev/sdc
         pvscan[12997] PV /dev/sdc online, VG vg is complete.
         VG vg complete

       use of --udevoutput:
       $ pvscan --cache --listvg --checkcomplete --vgonline --udevoutput /dev/sdb
       LVM_VG_NAME_INCOMPLETE='vg'
       $ pvscan --cache --listvg --checkcomplete --vgonline --udevoutput /dev/sdc
       LVM_VG_NAME_COMPLETE='vg'

       use of --listlvs:
       $ lvs -o name,devices vg
         LV    Devices
         lvol0 /dev/sdb(0)
         lvol1 /dev/sdc(0)
         lvol2 /dev/sdb(1),/dev/sdc(1)

       $ pvscan --cache --listlvs --checkcomplete /dev/sdb
         pvscan[13288] PV /dev/sdb online, VG vg incomplete (need 1).
         VG vg incomplete
         LV vg/lvol0 complete
         LV vg/lvol2 incomplete
       $ pvscan --cache --listlvs --checkcomplete /dev/sdc
         pvscan[13289] PV /dev/sdc online, VG vg is complete.
         VG vg complete
         LV vg/lvol1 complete
         LV vg/lvol2 complete

COLOPHON         top

       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, see ⟨https://github.com/lvmteam/lvm2/issues⟩.
       This page was obtained from the project's upstream Git repository
       ⟨git://sourceware.org/git/lvm2.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-11.)  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 2.03.25(2)-git (2024-05-1L6V)MAUTOACTIVATION(7)

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