LVM Cheat sheet

Material of this page is based on RedHat – LVM cheatsheet

This is a quick and dirty cheat sheet on LVM using Linux.

I have highlighted many of the common attributes for each command however this is not an extensive list, make sure you look up the man page for the command.

With the pvs, vgs and lvs commands, the number of -v defines that level of “verbosity”: the more v you put, the more verbose information is produced.

For example

pvs -vvvvv

Display, scanning, listing of physical volumes (PV)

pvdisplay -v 
pvs -v 
pvs -a

pvs attributes are:

  1. (a)llocatable
  2. e(x)ported
pvscan -v

Note: scans for disks for non-LVM and LVM disks

Diagnostic

lvmdump

lvmdump -d <dir>
dmsetup [info|ls|status]

Note: by default the lvmdump command creates a tar ball Physical Volumes

Adding

pvcreate /dev/sdb1

Create physical volume with specific UUID, used to recover volume groups (see miscellaneous section)

pvcreate --uuid <UUID> /dev/sdb1

Common Attributes that you may want to use:

-M2 create a LVM2 physical volume

Removing

checking

pvck -v /dev/sdb1

Note: check the consistency of the LVM metadata

Change physical attributes

do not allow allocation of extents on this drive

pvchange -x n /dev/sdb1

Common Attributes that you may want to use:–addtag add a tag
-x allowed to allocate extents
-u change the uuid

Moving

pvmove -v /dev/sdb2 /dev/sdb3

Note: moves any used extents from this volume to another volume, in readiness to remove that volume. However you cannot use this on mirrored volumes, you must convert back to non-mirror using “lvconvert -m 0”

Volume Groups

Display

vgdisplay -v
vgs -v
vgs -a -o +devices

vgs flags:

  • #PV – number of physical devices
  • #LV – number of configured volumes

vgs attributes are: 1. permissions (r)|(w)
2. resi(z)eable
3. e(x)ported
4. (p)artial
5. allocation policy – (c)ontiguous, c(l)ing, (n)ormal, (a)nywhere, (i)nherited
6. (c)luster

Scanning

vgscan -v

Creating

vgcreate VolData00 /dev/sdb1 /dev/sdb2 /dev/sdb3
vgcreate VolData00 /dev/sdb[123]

Use 32MB extent size

vgcreate VolData00 -s 32 /dev/sdb1

Common Attributes that you may want to use:

  • -l  maximum logical volumes
  • -p maximum physical volumes
  • -s physical extent size (default is 4MB)
  • -A autobackup

Extending

vgextend VolData00 /dev/sdb3

Reducing

vgreduce VolData00 /dev/sdb3

vgreduce --removemissing --force VolData00

Removing

vgremove VolData00

Common Attributes that you may want to use:

  • -f force the removal of any logical volumes

Checking

vgck VolData00

Note: checks the consistency of the LVM metadata

Change volume attributes

vgchange -a n VolData00

Common Attributes that you may want to use:

  • -a control availability of volumes within the group
  • -l  maximum logical volumes
  • -p maximum physical volumes
  • -s physical extent size (default is 4MB)
  • -x resizable yes or no (see VG status in vxdisplay)

Renaming

vgrename VolData00 Data_Vol_01

Note: the volume group must not have any active logical volumes

Converting metadata type

vgconvert -M2 VolData00

Note: vgconvert allows you to convert from one type of metadata format to another for example from LVM1 to LVM2

Merging

vgmerge New_Vol_Group Old_Vol_Group

Note: the old volumes group will be merged into the new volume group

Spliting

vgsplit Old_Vol_Group New_Vol_Group [physical volumes] [-n logical volume name]

Importing

vgimport VolData00

Common Attributes that you may want to use:

  • -a import all exported volume groups

Exporting

To see if a volume has already been export use “vgs” and look at the third attribute should be a x

vgexport VolData00

Common Attributes that you may want to use:

  • -a export all inactive volume groups

Backing up

Backup to default location (/etc/lvm/backup)

vgcfgbackup VolData00

Backup to specific location

vgcfgbackup -f /var/backup/VolData00_bkup VolData00

Note: the backup is written in plain text and are by default located in /etc/lvm/backup

Restoring

vgcfgrestore -f /var/backup/VolData00_bkup VolData00

Common Attributes that you may want to use:-l list backups of file
-f backup file
-M metadataype 1 or 2

Cloning

vgimportclone /dev/sdb1

Note: used to import and rename duplicated volume group

Special files

vgmknodes VolData00

Note: recreates volume group directory and logical volume special files in /dev

Logical Volumes

Display

lvdisplay -v

display mirror volumes

lvdisplay --maps
lvs -v
lvs -a -o +devices

lvs commands for mirror volumes:

lvs -a -o +devices
lvs -a -o +seg_pe_ranges --segments

lvs attributes are:

  1. volume type: (m)irrored, (M)irrored without initail sync, (o)rigin, (p)vmove, (s)napshot, invalid (S)napshot, (v)irtual, mirror (i)mage  mirror (I)mage out-of-sync, under (c)onversion
  2. permissions: (w)rite, (r)ead-only
  3. allocation policy – (c)ontiguous, c(l)ing, (n)ormal, (a)nywhere, (i)nherited
  4. fixed (m)inor
  5. state: (a)ctive, (s)uspended, (I)nvalid snapshot, invalid (S)uspended snapshot, mapped (d)evice present with-out tables,  mapped device present with (i)nactive table
  6. device (o)pen (mounted in other words)

Scanning

lvscan -v
lvmdiskscan

Creating

Plain old volume

lvcreate -L 10G VolData00

Plain old volume but with a specific name web01:

lvcreate -L 10G -n web01 VolData00

Plain old volume but on a specific disk

lvcreate -L 10G VolData00 /dev/sdb1

A striped volume called lvol1

lvcreate -i 3 -I 32 -L 24G -n lvol1 vg01

Mirrored volume:

lvcreate -L 10G -m1 -n data01 vg01

Mirrored volume without a mirror log file:

lvcreate -L 10M -m1 --mirrorlog core -n data01 vg01

Common Attributes that you may want to use:

  • -L size of the volume [kKmMgGtT]
  • -l number of extents
  • -C contiguous [y|n]
  • -i stripes
  • -I stripe size
  • -m mirrors
  • –mirrorlog
  • -n volume name

Extending

lvextend -L 20M /dev/VolData00/vol01

Common Attributes that you may want to use:-L size of the volume [kKmMgGtT]
-l number of extents
-C contiguous [y|n]
-i stripes
-I stripe size

Note: you can extend a ext2/ext3 filesystem using the “resize2fs” or “fsadm” command

fsadm resize /dev/VolData01/data01
resize2fs -p /dev/mapper/VolData01-data01 [size]

The -p option displays bars of progress while extending the filesystem

reducing/resizing

lvreduce -L 5G /dev/VolData00/vol01
lvresize -L 5G /dev/VolData00/vol01

Note: rounding will occur when extending and reducing volumes to the next extent (4MB by default), you can use resize2fs or fsadm to shrink the filesystemfsadm resize /dev/VolData01/data01 [size]
resize2fs -p /dev/mapper/VolData01-data01 [size]

removing

lvremove /dev/VolData00/vol01

adding a mirror to a non-mirrored volume

lvconvert -m1 --mirrorlog core /dev/VolData00/vol01 /dev/sdb2

change volume attributes

lvchange -a n /dev/VolData00/vol01

Common Attributes that you may want to use:-a availability
-C contiguous [y|n]

renaming

lvrname /dev/VolData00/vol_old /dev/VolData00/vol_new

snapshotting

lvcreate --size 100M --snapshot -name snap /dev/vg01/data01

Miscellaneous

Simulating a disk failure

dd if=/dev/zero of=/dev/sdb2 count=10

Repairing a failed mirror no LVM corruption

Check volume, persume /dev/sdb2 has failed:

lvs -a -o +devices

Remove the failed disk from the volume (if not already done so) , this will convert volume into a non-mirrored volume

vgreduce --removemissing --force VolData00

Replace the disk physically, remember to partion it with type 8e:

fdisk /dev/sdb

……..

Add new disk to LVM

pvcreate /dev/sdb2

Add the disk back into volume group

vgextend VolData00 /dev/sdb2

Mirror up the volume:

lvconvert -m1 --mirrorlog core /dev/VolData00/vol02 /dev/sdb2

Repair corrupt LVM metadata without replacing drive

Attempt to bring the volume group online:

vgchange -a y VolData00

Restore the LVM configation

vgcfgrestore VolData00

Attempt to bring the volume group online:

vgchange -a y VolData00

File system check:

e2fsck /dev/VolData00/data01

Repair corrupt LVM metadata and replace the faulty disk

# attempt to bring the volume group online but you get UUID conflict errors make note of the UUID number
vgchange -a y VolData00
vgchange -a n VolData00

## sometimes it my only be a logical volume problem
lvchange -a y /dev/VolData00/web02
lvchange -a n /dev/Voldata00/web02

## replace the disk physically, remember to partion it with type 8e
fdisk /dev/sdb
……..

# after replacing the faulty drive the disk must have the previuos UUID number or you can get it from /etc/lvm directory
pvcreate –uuid <previous UUID number taken from above command> /dev/sdb2

# Restore the LVM configation
vgcfgrestore VolData00

# attempt to bring the volume group online or logical volume
vgchange -a y VolData00
lvchange -a y /dev/VolData00/web02

# file system check
e2fsck /dev/VolData00/data01Note: if you have backed the volume group configuration you can obtain the UUID number in the backup file by default located in /etc/lvm/backup or running “pvs -v”

Directory and Files

Directories

  • /etc/lvm                    – default lvm directory location
  • /etc/lvm/backup         – where the automatic backups go
  • /etc/lvm/cache          – persistent filter cache
  • /etc/lvm/archive        – where automatic archives go after a volume group change
  • /var/lock/lvm             – lock files to prevent metadata corruption

Files

  • /etc/lvm/lvm.conf       – main lvm configuration file
  • $HOME/.lvm              – lvm history