LVM Cheat Sheet

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Logical Volume Manager (LVM)

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 command.

With the pvs, vgs and lvs commands, the number of verboses added the more verbose information for example pvs -vvvvv 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

  1. Files

/etc/lvm/lvm.conf - main lvm configuration file $HOME/.lvm - lvm history Tools diagnostic lvmdump lvmdump -d <dir> dmsetup [info|ls|status]

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

pvdisplay -v pvs -v pvs -a pvs --segments (see the disk segments used)

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

    1. 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

    1. do not allow allocation of extents on this drive, however the partition must be in a vg otherwise you get an error

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:

  1. PV - number of physical devices
  2. 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]

    1. 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, LVM2 offers bigger capacity, clustering and mirroring merging # the old volumes group will be merged into the new volume group vgmerge New_Vol_Group Old_Vol_Group

Note: you must unmount any fielsystems and deactivate the vg that is being merged "vgchange -a n <vg>", then you can activiate it again afterwards "vgchange -a y <vg>", then perform a vgscan, dont forget to backup the configuration 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

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

vgcfgbackup VolData00

  1. Backup to specific location

vgcfgbackup -f /var/backup/VolData00_bkup VolData00

  1. Backup to specific location all volume groups (notice the %s)

vgcfgbackup -f /var/backup/vg_backups_%s

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 lvdisplay --maps display mirror volumes

lvs -v lvs -a -o +devices

    1. lvs commands for mirror volumes

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

    1. Stripe size

lvs -v --segments lvs -a -o +stripes,stripesize

    1. use complex command

lvs -a -o +devices,stripes,stripesize,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

    1. plain old volume

lvcreate -L 10M VolData00

    1. plain old volume but use extents, use 10 4MB extents (if extent size is 4MB)

lvcreate -l 10 VolData00

    1. plain old volume but with a specific name web01

lvcreate -L 10M -n web01 VolData00

    1. plain old volume but on a specific disk

lvcreate -L 10M VolData00 /dev/sdb1

    1. a striped volume called lvol1 (note the captial i for the stripe size), can use -l (extents) instead of -L

lvcreate -i 3 -L 24M -n lvol1 vg01

    1. Mirrored volume

lvcreate -L 10M -m1 -n data01 vg01

    1. 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 extendingthe 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

Note: you can also use the above command to remove a unwanted log removing a mirror from a mirrored volume

lvconvert -m0 /dev/VolData00/vol01 /dev/sdb2

Note: the disk in the command is the one you want to remove Mirror a volume that has stripes lvconvert --stripes 3 -m1 --mirrorlog core /dev/VolData00/data01 /dev/sdd1 /dev/sde1 /devsdf1 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

  1. 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

    1. replace the disk physically, remember to partion it with type 8e

fdisk /dev/sdb ........

    1. add new disk to LVM

pvcreate /dev/sdb2

    1. add the disk back into volume group

vgextend VolData00 /dev/sdb2

    1. 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

  1. Restore the LVM configation

vgcfgrestore VolData00

  1. attempt to bring the volume grou online

vgchange -a y VolData00

  1. file system check

e2fsck /dev/VolData00/data01 corrupt LVM metadata but replacing the faulty disk

  1. 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

    1. sometimes it my only be a logical volume problem

lvchange -a y /dev/VolData00/web02 lvchange -a n /dev/Voldata00/web02

    1. replace the disk physically, remember to partion it with type 8e

fdisk /dev/sdb ........

  1. 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

  1. Restore the LVM configation

vgcfgrestore VolData00

  1. attempt to bring the volume group online or logical volume

vgchange -a y VolData00 lvchange -a y /dev/VolData00/web02

  1. 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"

Source: Red Hat LVM Cheatsheet