Chris Tyler - Fedora Linux

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

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 .

To list the PVs present, use pvs or 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]

LV Status available

# open 1

LV Size 512.00 MB

Current LE 128

Segments 1

Allocation inherit

Read ahead sectors 0

Block device 253:3

--- Logical volume ---

LV Name /dev/main/multimedia-snap

VG Name main

LV UUID 7U5wVQ-qIWU-7bcz-J4vT-zAPh-xGVN-CDNfjx

LV Write Access read/write

LV snapshot status active destination for /dev/main/multimedia

LV Status available

# open 0

LV Size 512.00 MB

Current LE 128

COW-table size 128.00 MB

COW-table LE 32

Allocated to snapshot 0.02%

Snapshot chunk size 8.00 KB

Segments 1

Allocation inherit

Read ahead sectors 0

Block device 253:6

This display shows the volume group, attributes (again, see man lvm ), and logical volume size. Additional information is shown for snapshot volumes and LVs that are being copied or moved between PVs. The Block device shown in the lvdisplay output is the major and minor device number.

To increase the size of a logical volume, use the lvextend command:

# lvextend /dev/main/multimedia --size 1G

Extending logical volume multimedia to 1.00 GB

Logical volume multimedia successfully resized

Specify the LV device as the first argument, and use the --size option to specify the new size for the volume. Use a numeric size with one of the size suffixes from Table 6-2 as the value for the --size option.

Table 6-2. Size suffixes used by LVM

Once you have resized the LV, resize the filesystem contained inside:

#

resize2fs /dev/main/multimedia

resize2fs 1.39 (29-May-2006)

Resizing the filesystem on /dev/main/multimedia to 1048576 (1k) blocks.

The filesystem on /dev/main/multimedia is now 1048576 blocks long.

Note that you do not need to specify the filesystem size; the entire LV size will be used.

If the resize2fs fails with the message No space left on device, the new size is too large for the existing allocation tables

Before reducing the size of a logical volume, you must first reduce the size of the filesystem inside the LV. This must be done when the filesystem is unmounted: