LVM Cheat Sheet

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Directory and Files
Directories 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

Tools
diagnostic With the pvs, vgs and lvs commands, the number of verboses added the more verbose information:

pvs -vvvvv

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

Note: by default the lvmdump command creates a tarball

Physical Volumes
display pvdisplay -v

pvs -v
pvs -a

pvs attributes are:

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


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

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 pvremove /dev/sdb1
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: check 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

lvs -v

Display the mapping of logical extents to physical volumes and physical extents
lvdisplay --maps

Map physical extents to logical extents
pvs --segments -o+lv_name,seg_start_pe,segtype

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 10M VolData00

plain old volume but with a specific name web01
lvcreate -L 10M -n web01 VolData00

plain old volume but on a specific disk
lvcreate -L 10M VolData00 /dev/sdb1

a striped volume called lvol1 (note the captial i for the stripe size)
lvcreate -i 3 -I 32 -L 24M -n lvol1 vg01 Mirrored volume
lvcreate -L 10M -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 5M /dev/VolData00/vol01

lvresize -L 5M /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 filesystem

fsadm 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 lvrename /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
reparing 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

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 grou online
vgchange -a y VolData00

file system check
e2fsck /dev/VolData00/data01

corrupt LVM metadata but replacing 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 may 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/data01

Note: 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"



Original: http://www.datadisk.co.uk/html_docs/redhat/rh_lvm.htm