Logical Volume Manager – LVM

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 # 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 ## 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, 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: #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, 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	## Backup to default location (/etc/lvm/backup) vgcfgbackup VolData00 # Backup to specific location vgcfgbackup -f /var/backup/VolData00_bkup VolData00 # 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 ## lvs commands for mirror volumes lvs -a -o +devices lvs -a -o +seg_pe_ranges –segments ## Stripe size lvs -v –segments lvs -a -o +stripes,stripesize ## 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	## plain old volume lvcreate -L 10M VolData00 ## plain old volume but use extents, use 10 4MB extents (if extent size is 4MB) lvcreate -l 10 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), can use -l (extents) instead of -L lvcreate -i 3 -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 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 # 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 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/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”