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Chapter 13. Logical volume activation
By default, when you create a logical volume, it is in an active state. A logical volume that is an active state can be used through a block device. An activated logical volume is accessible and is subject to change.
There are various circumstances, where you need to make an individual logical volume inactive and therefore unknown to the kernel. You can activate or deactivate individual logical volume with the -a
option of the lvchange
command.
The following is the format to deactivate an individual logical volume:
# lvchange -an vg/lv
The following is the format to activate an individual logical volume:
# lvchange -ay vg/lv
You can activate or deactivate all of the logical volumes in a volume group with the -a
option of the vgchange
command. This is the equivalent of running the lvchange -a
command on each individual logical volume in the volume group.
The following is the format to deactivate all of the logical volumes in a volume group:
# vgchange -an vg
The following is the format to activate all of the logical volumes in a volume group:
# vgchange -ay vg
During manual activation, the systemd
automatically mounts LVM volumes with the corresponding mount point from the /etc/fstab
file unless the systemd-mount
unit is masked.
13.1. Controlling autoactivation of logical volumes and volume groups
Autoactivation of a logical volume refers to the event-based automatic activation of a logical volume during system startup. As devices become available on the system (device online events), systemd/udev
runs the lvm2-pvscan
service for each device. This service runs the pvscan --cache -aay device
command, which reads the named device. If the device belongs to a volume group, the pvscan
command will check if all of the physical volumes for that volume group are present on the system. If so, the command will activate logical volumes in that volume group.
You can set the autoactivation property on a VG or LV. When the autoactivation property is disabled, the VG or LV will not be activated by a command doing autoactivation, such as vgchange
, lvchange
, or pvscan
using -aay
option. If autoactivation is disabled on a VG, no LVs will be autoactivated in that VG, and the autoactivation property has no effect. If autoactivation is enabled on a VG, autoactivation can be disabled for individual LVs.
Procedure
You can update the autoactivation settings in one of the following ways:
Control autoactivation of a VG using the command line:
# vgchange --setautoactivation <y|n>
Control autoactivation of a LV using the command line:
# lvchange --setautoactivation <y|n>
Control autoactivation of a LV in the
/etc/lvm/lvm.conf
configuration file using one of the following configuration options:global/event_activation
When
event_activation
is disabled,systemd/udev
will autoactivate logical volume only on whichever physical volumes are present during system startup. If all physical volumes have not appeared yet, then some logical volumes may not be autoactivated.activation/auto_activation_volume_list
Setting
auto_activation_volume_list
to an empty list disables autoactivation entirely. Settingauto_activation_volume_list
to specific logical volumes and volume groups limits autoactivation to those logical volumes.
Additional resources
-
/etc/lvm/lvm.conf
configuration file -
lvmautoactivation(7)
man page
13.2. Controlling logical volume activation
You can control the activation of logical volume in the following ways:
-
Through the
activation/volume_list
setting in the/etc/lvm/conf
file. This allows you to specify which logical volumes are activated. For information about using this option, see the/etc/lvm/lvm.conf
configuration file. - By means of the activation skip flag for a logical volume. When this flag is set for a logical volume, the volume is skipped during normal activation commands.
Alternatively, you can use the --setactivationskip y|n
option with the lvcreate
or the lvchange
commands to enable or disable the activation skip flag.
Procedure
You can set the activation skip flag on a logical volume in the following ways:
To determine whether the activation skip flag is set for a logical volume run the
lvs
command, which displays thek
attribute as in the following example:# lvs vg/thin1s1 LV VG Attr LSize Pool Origin thin1s1 vg Vwi---tz-k 1.00t pool0 thin1
You can activate a logical volume with the
k
attribute set by using the-K
or--ignoreactivationskip
option in addition to the standard-ay
or--activate y
option.By default, thin snapshot volumes are flagged for activation skip when they are created. You can control the default activation skip setting on new thin snapshot volumes with the
auto_set_activation_skip
setting in the/etc/lvm/lvm.conf
file.The following command activates a thin snapshot logical volume that has the activation skip flag set:
# lvchange -ay -K VG/SnapLV
The following command creates a thin snapshot without the activation skip flag:
# lvcreate -n SnapLV -kn -s vg/ThinLV --thinpool vg/ThinPoolLV
The following command removes the activation skip flag from a snapshot logical volume:
# lvchange -kn VG/SnapLV
Verification steps
Verify if a thin snapshot without the activation skip flag has been created:
# lvs -a -o +devices,segtype LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert Devices Type SnapLV vg Vwi-a-tz-- 100.00m ThinPoolLV ThinLV 0.00 thin ThinLV vg Vwi-a-tz-- 100.00m ThinPoolLV 0.00 thin ThinPoolLV vg twi-aotz-- 100.00m 0.00 10.94 ThinPoolLV_tdata(0) thin-pool [ThinPoolLV_tdata] vg Twi-ao---- 100.00m /dev/sdc1(1) linear [ThinPoolLV_tmeta] vg ewi-ao---- 4.00m /dev/sdd1(0) linear [lvol0_pmspare] vg ewi------- 4.00m /dev/sdc1(0) linear
13.3. Activating shared logical volumes
You can control logical volume activation of a shared logical volume with the -a
option of the lvchange
and vgchange
commands, as follows:
Command | Activation |
---|---|
| Activate the shared logical volume in exclusive mode, allowing only a single host to activate the logical volume. If the activation fails, as would happen if the logical volume is active on another host, an error is reported. |
| Activate the shared logical volume in shared mode, allowing multiple hosts to activate the logical volume concurrently. If the activation fails, as would happen if the logical volume is active exclusively on another host, an error is reported. If the logical type prohibits shared access, such as a snapshot, the command will report an error and fail. Logical volume types that cannot be used concurrently from multiple hosts include thin, cache, raid, and snapshot. |
| Deactivate the logical volume. |
13.4. Activating a logical volume with missing devices
You can control whether LVs that are missing devices can be activated by using the lvchange
command with the --activationmode partial|degraded|complete
option. The values are described below:
Activation Mode | Meaning |
---|---|
complete | Allows only logical volumes with no missing physical volumes to be activated. This is the most restrictive mode. |
degraded | Allows RAID logical volumes with missing physical volumes to be activated. |
partial | Allows any logical volume with missing physical volumes to be activated. This option should be used for recovery or repair only. |
The default value of activationmode
is determined by the activationmode
setting in the /etc/lvm/lvm.conf
file. It is used if no command line option is given.
Additional resources
-
lvmraid(7)
man page