Fedora Linux

pvmove	Migrates data from one physical volume to another
lvcreate	Creates a logical volume or snapshot LV
lvextend	Grows a logical volume
lvreduce	Shrinks a logical volume
lvresize	Grows or shrinks a logical volume
vgscan	Scans block devices for volume groups (necessary when using a rescue-mode boot)

You can also enter any of these subcommands as the first argument on the lvm command line:

# lvm lvs
LV VG Attr LSize Origin Snap% Move Log Copy%
home main -wi-ao 1.00G
multimedia main -wi-ao 512.00M
root main -wi-ao 9.77G
swap main -wi-ao 1.00G

Symbolic links have been set up from /usr/sbin/<subcommand > to /usr/sbin/lvm , so you can just type the name of the subcommand at the regular bash shell prompt:

# ls -l /usr/sbin/lvs
lrwxrwxrwx 1 root root 3 Mar 20 14:49 /usr/sbin/lvs -> lvm
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy%
home main -wi-ao 1.00G
multimedia main -wi-ao 512.00M
root main -wi-ao 9.77G
swap main -wi-ao 1.00G

The symbolic links are not available when you are in rescue mode (see Lab 10.6, 'Using Rescue Mode on an Installation Disc'), so it's important to remember that you can also use these subcommands as arguments to the lvm command (for example, when in rescue mode, type lvm lvdisplay instead of lvdisplay).

6.1.1.3.1. LVM device names

Logical volumes can be accessed using any of three different device nodes:

? In the /dev/mapper directory, the entry named by the pattern vg - lv . For example, if the volume group main had a logical volume named home , it could be accessed using the name /dev/mapper/main- home .

? There is a separate directory in /dev for each volume group, and an entry for each logical volume within that directory. Our sample volume could be accessed as /dev/main/home . These names are slightly shorter to type than the ones in /dev/mapper , and are actually symbolic links to the longer names.

? Using /dev/dm-<number> , where <number> is a number sequentially assigned when volume groups are initially scanned at boot time (or when the LV is created, if it was created after the last boot). If a volume is the second one found during the vgscan , it can be accessed as /dev/dm-1 (the first one found is numbered 0 ). These names are a bit harder to use, since the VG and LV are not identified; to find the corresponding entry in /dev/mapper , compare the minor device numbers. You cannot use these names in rescue mode.

In addition to these device node names, some LVM commands allow the volume group and logical volume names to be written as vg / lv for example, main/multimedia refers to the LV multimedia within the VG main.

6.1.1.3.2. Getting information about LVM elements

To discover the VGs present on your system, use the vgs command:

# vgs
VG #PV #LV #SN Attr VSize VFree
main 2 4 0 wz--n- 20.04G 7.78G

This shows the volume group name, the number of physical volumes, logical volumes, and snapshots; attributes (see the manpage for lvm for details); the volume group size; and the amount of space that is not assigned to a logical volume.

vgdisplay shows the same information as vgs but in a more verbose form:

# vgdisplay
--- Volume group ---
VG Name main
System ID
Format lvm2
Metadata Areas 2