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
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
vgs# 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
Metadata Sequence No 51
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 4
Open LV 4
Max PV 0
Cur PV 2
Act PV 2
VG Size 20.04 GB
PE Size 4.00 MB
Total PE 5131
Alloc PE / Size 3140 / 12.27 GB
Free PE / Size 1991 / 7.78 GB
VG UUID 13X0pY-5Vnq-3KlU-7Qlu-sHUc-wrup-zsHipP
The VG UUID at the bottom is a unique ID number placed in the disk
label of each PV to identify that it is part of this volume group.
If you have more than one VG present and only want to see information about a specific one, you can specify a volume group name as an argument to vgdisplay or vgs .pvs pvdisplay
# pvs
PV VG Fmt Attr PSize PFree
/dev/hdc3 main lvm2 a- 20.04G 7.77G
/dev/sdb1 main lvm2 a- 4.00M 4.00M
# pvdisplay
--- Physical volume ---
PV Name /dev/hdc3
VG Name main
PV Size 20.04 GB / not usable 0
Allocatable yes
PE Size (KByte) 4096
Total PE 5130
Free PE 1990
Allocated PE 3140
PV UUID RL2wrh-WMgl-pyaR-bHt4-6dCv-23Fd-kX1gvT
--- Physical volume ---
PV Name /dev/sdb1
VG Name main
PV Size 4.00 MB / not usable 0
Allocatable yes
PE Size (KByte) 4096
Total PE 1
Free PE 1
Allocated PE 0
PV UUID HvryBh-kGrM-c10y-yw1v-u8W3-r2LN-5LrLrJ
In this case, there are two PVs present: /dev/hdc3 (an IDE hard disk partition) and /dev/sdb1 (a USB disk I was playing with). Both are part of the VG main . The display shows the attributes (see man lvm ), size, and amount of unallocated space.
In a similar way, you can see logical volume information with lvs or lvdisplay :
# lvs
LV VG Attr LSize Origin Snap% Move Log Copy%
home main -wi-ao 1.00G
multimedia main owi-ao 512.00M
multimedia-snap main swi-a- 128.00M multimedia 0.02
root main -wi-ao 9.77G
swap main -wi-ao 1.00G
# lvdisplay
--- Logical volume ---
LV Name /dev/main/root
VG Name main
LV UUID LaQgYA-jiBr-G02i-y64m-90fT-viBp-TuZ9sC
LV Write Access read/write
LV Status available
# open 1
LV Size 9.77 GB
Current LE 2500
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:0
...(Lines snipped)...
--- Logical volume ---
LV Name /dev/main/multimedia
VG Name main
LV UUID f7zJvh-H21e-fSn7-llq3-Ryu1-p1FQ-PTAoNC
LV Write Access read/write
LV snapshot status source of
/dev/main/multimedia-snap [active]