Installation guide

Appendix A. The Device Mapper
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Event number
The current number of events received. Issuing a dmsetup wait n command allows the user
to wait for the n'th event, blocking the call until it is received.
Major, minor
Major and minor device number
Number of targets
The number of fragments that make up a device. For example, a linear device spanning 3 disks
would have 3 targets. A linear device composed of the beginning and end of a disk, but not the
middle would have 2 targets.
UUID
UUID of the device.
The following example shows partial output for the dmsetup info command.
[root@ask-07 ~]# dmsetup info
Name: testgfsvg-testgfslv1
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 0
Event number: 0
Major, minor: 253, 2
Number of targets: 2
UUID: LVM-K528WUGQgPadNXYcFrrf9LnPlUMswgkCkpgPIgYzSvigM7SfeWCypddNSWtNzc2N
...
Name: VolGroup00-LogVol00
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 0
Major, minor: 253, 0
Number of targets: 1
UUID: LVM-tOcS1kqFV9drb0X1Vr8sxeYP0tqcrpdegyqj5lZxe45JMGlmvtqLmbLpBcenh2L3
A.2.2. The dmsetup ls Command
You can list the device names of mapped devices with the dmsetup ls command. You can
list devices that have at least one target of a specified type with the dmsetup ls --target
target_type command. For other options of the dmsetup ls, see the dmsetup man page.
The following example shows the command to list the device names of currently configured mapped
devices.
[root@ask-07 ~]# dmsetup ls
testgfsvg-testgfslv3 (253, 4)
testgfsvg-testgfslv2 (253, 3)
testgfsvg-testgfslv1 (253, 2)
VolGroup00-LogVol01 (253, 1)
VolGroup00-LogVol00 (253, 0)
The following example shows the command to list the devices names of currently configured mirror
mappings.