How to create new volume group ?
1.List the physical disks which were brought under logical volume manager control using pvcreate command.
[root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 lvm2 a- 511.98m 511.98m /dev/sde lvm2 a- 512.00m 512.00m /dev/sdf lvm2 a- 5.00g 5.00g [root@mylinz ~]#
[root@mylinz ~]# vgcreate uavg /dev/sdd1 Volume group "uavg" successfully created [root@mylinz ~]#
3.Verify the new volume group.
[root@mylinz ~]# vgs uavg VG #PV #LV #SN Attr VSize VFree uavg 1 0 0 wz--n- 508.00m 508.00m [root@mylinz ~]# [root@mylinz ~]# pvs |grep uavg /dev/sdd1 uavg lvm2 a- 508.00m 508.00m [root@mylinz ~]#
4.For detailed volume group information,use below mentioned command.
[root@mylinz ~]# vgdisplay uavg --- Volume group --- VG Name uavg System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 1 VG Access read/write VG Status resizable MAX LV 0 Cur LV 0 Open LV 0 Max PV 0 Cur PV 1 Act PV 1 VG Size 508.00 MiB PE Size 4.00 MiB Total PE 127 Alloc PE / Size 0 / 0 Free PE / Size 127 / 508.00 MiB VG UUID c87FyZ-5DND-oQ3n-iTh1-Vb1f-nBML-vUBUE9 [root@mylinz ~]#
We can rename the volume group in Redhat Linux using vgrename command.The rename can be done on the fly without any impact. Here i am going to show the vgrename and proving that no impact on this activity.
1.List the currently mounted from volume group “uavg”
[root@mylinz ~]# df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/uavg-ualvol1
51M 4.9M 43M 11% /mnt
[root@mylinz ~]#
2.List the available volume group.
[root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0
3.Rename the volume group using “vgrename” command.
[root@mylinz ~]# vgrename uavg uavg_new Volume group "uavg" successfully renamed to "uavg_new" [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg_new 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
4.Check the volume status .You can see still volume is available for operation.
[root@mylinz ~]# df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/uavg-ualvol1
51M 4.9M 43M 11% /mnt
[root@mylinz ~]#
[root@mylinz ~]# cd /mnt
[root@mylinz mnt]# touch 3 4 5 6
[root@mylinz mnt]# ls -lrt
total 18
drwx------. 2 root root 12288 Aug 6 22:55 lost+found
-rw-r--r--. 1 root root 0 Aug 7 00:32 1
-rw-r--r--. 1 root root 0 Aug 7 00:32 7
-rw-r--r--. 1 root root 0 Aug 12 21:17 6
-rw-r--r--. 1 root root 0 Aug 12 21:17 5
-rw-r--r--. 1 root root 0 Aug 12 21:17 4
-rw-r--r--. 1 root root 0 Aug 12 21:17 3
[root@mylinz mnt]#
5.But the volume is still reflecting the old device.This can be removed after remounting the volume.This can be down when you have down time for the server.Please don;t forget to update “fstab” according to the new volume group name.
[root@mylinz ~]# umount /mnt
[root@mylinz ~]# mount -t ext4 /dev/mapper/uavg_new-ualvol1 /mnt
[root@mylinz ~]# df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/uavg_new-ualvol1
51M 4.9M 43M 11% /mnt
[root@mylinz ~]# vgs
VG #PV #LV #SN Attr VSize VFree
uavg_new 1 1 0 wz--n- 508.00m 456.00m
vg_mylinz 1 2 0 wz--n- 19.51g 0
[root@mylinz ~]#
How to Extend the volume group ?
Volume group can be extend on the fly by adding new disks or LUNS to the existing volume group.
1.List the volume group .
[root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
2.List the available physical volumes for extending the volume group “uavg”.
Check out if you have any doubt to create new physical volume from new disks or LUNS.
[root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 a- 508.00m 456.00m /dev/sde lvm2 a- 512.00m 512.00m /dev/sdf lvm2 a- 5.00g 5.00g [root@mylinz ~]#
3.Let me choose “sde” to extend volume group “uavg”.
[root@mylinz ~]# vgextend uavg /dev/sde Volume group "uavg" successfully extended [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 2 1 0 wz--n- 1016.00m 964.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
From the above output ,you can see volume group “uavg” has been extended successfully.
4.Check the “pvs” command output. /dev/sde will show as part of “uavg” now.
[root@mylinz ~]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 vg_mylinz lvm2 a- 19.51g 0 /dev/sdd1 uavg lvm2 a- 508.00m 456.00m /dev/sde uavg lvm2 a- 508.00m 508.00m /dev/sdf lvm2 a- 5.00g 5.00g [root@mylinz ~]#
How to scan a disks for LVM ?
You need to scan a LVM disks whenever there is a hardware changes on your server.Hardware changes may be a newly added or removed disks which will be hotplug disks or new disks added to SAN systems.
[root@mylinz ~]# vgscan Reading all physical volumes. This may take a while... Found volume group "uavg" using metadata type lvm2 Found volume group "vg_mylinz" using metadata type lvm2 [root@mylinz ~]#
How to decrease the volume group size ? or How to remove disks from LVM ?
Disks can be removed from volume group if its not used for any volumes.
1.First find out the disks which we are planning to remove it from volume group is not used for any volumes using below mentioned commands.
[root@mylinz ~]# lvs -a -o +devices LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices ualvol1 uavg -wi-a- 52.00m /dev/sdd1(0) lv_root vg_mylinz -wi-ao 16.54g /dev/sda2(0) lv_swap vg_mylinz -wi-ao 2.97g /dev/sda2(4234) [root@mylinz ~]# pvs -a -o +devices |grep uavg /dev/sdd1 uavg lvm2 a- 508.00m 456.00m /dev/sdd1(0) /dev/sdd1 uavg lvm2 a- 508.00m 456.00m /dev/sde uavg lvm2 a- 508.00m 508.00m /dev/uavg/ualvol1 -- 0 0 [root@mylinz ~]#
From the above commands output,we can see disk “sde” is not used for any volumes (lvs command output) in volume group “uavg” .
2.Check the disk details. From this details you can confirm ,PE (i.e physical extends) are not used in VG. (Total PE=127 & Free PE=127).
[root@mylinz ~]# pvdisplay /dev/sde --- Physical volume --- PV Name /dev/sde VG Name uavg PV Size 512.00 MiB / not usable 4.00 MiB Allocatable yes PE Size 4.00 MiB Total PE 127 Free PE 127 Allocated PE 0 PV UUID FadWLT-LjD8-v8VB-pboY-eZbK-vYpE-ZWq0i9 [root@mylinz ~]#
3.List the volume group details before removing the physical volume.
[root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 2 1 0 wz--n- 1016.00m 964.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]# vgdisplay uavg --- Volume group --- VG Name uavg System ID Format lvm2 Metadata Areas 2 Metadata Sequence No 9 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 0 Max PV 0 Cur PV 2 Act PV 2 VG Size 1016.00 MiB PE Size 4.00 MiB Total PE 254 Alloc PE / Size 13 / 52.00 MiB Free PE / Size 241 / 964.00 MiB VG UUID c87FyZ-5DND-oQ3n-iTh1-Vb1f-nBML-vUBUE9 [root@mylinz ~]#
4.Now we are ready to remove the “/dev/sde” from volume group “uavg”.
[root@mylinz ~]# vgreduce uavg /dev/sde Removed "/dev/sde" from volume group "uavg" [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]# vgdisplay uavg --- Volume group --- VG Name uavg System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 10 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 0 Max PV 0 Cur PV 1 Act PV 1 VG Size 508.00 MiB PE Size 4.00 MiB Total PE 127 Alloc PE / Size 13 / 52.00 MiB Free PE / Size 114 / 456.00 MiB VG UUID c87FyZ-5DND-oQ3n-iTh1-Vb1f-nBML-vUBUE9 [root@mylinz ~]#
From the above outputs ,you can see #PV reduced to “1” and volume group size also reduced.
How to activate and Deactivate the volume group ?
By default volume group will be in active mode. But some circumstances,you need to put the volume group in disabled mode or inactive mode thus unknown to Linux kernel. Here we will see how to activate and deactivate the volume group.
1.List the volume groups.
[root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
2.Deactive the volume group “uavg”
[root@mylinz ~]# vgchange -a n uavg 0 logical volume(s) in volume group "uavg" now active [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
you can not deactivate VG if any opened volumes from that volumegroup. You have to unmount all the volumes from the volume group before deactivating it .You will get below error if any volumes in opened state .
[root@mylinz ~]# vgchange -a n uavg Can't deactivate volume group "uavg" with 1 open logical volume(s) [root@mylinz ~]#
3.Check the volume status.It will be in “Not Available” status.
[root@mylinz ~]# lvdisplay /dev/uavg/ualvol1 --- Logical volume --- LV Name /dev/uavg/ualvol1 VG Name uavg LV UUID 6GB8TR-ih7d-vg7J-xCLE-A8OH-gmwy-3XLyOb LV Write Access read/write LV Status NOT available LV Size 52.00 MiB Current LE 13 Segments 1 Allocation inherit Read ahead sectors auto [root@mylinz ~]#
4.You can activate the volume group use same command with different options.
[root@mylinz ~]# vgchange -a y uavg 1 logical volume(s) in volume group "uavg" now active [root@mylinz ~]# lvdisplay /dev/uavg/ualvol1 --- Logical volume --- LV Name /dev/uavg/ualvol1 VG Name uavg LV UUID 6GB8TR-ih7d-vg7J-xCLE-A8OH-gmwy-3XLyOb LV Write Access read/write LV Status available # open 0 LV Size 52.00 MiB Current LE 13 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2 [root@mylinz ~]#
5.Mount the volume .We are back to normal operation.
[root@mylinz ~]# mount -t ext4 /dev/mapper/uavg-ualvol1 /mnt [root@mylinz ~]#
How to backup & restore the LVM volumegroup metadata ?
Automatically Metadata backups and archives are created whenever you create new volume group Linux system.By default backup stored in /etc/lvm/backup and archives are stored in /etc/lvm/archive .We can also manually backup the lvm configuration using “vgcfgbackup” command.
1.Run “vgcfgbackup” command to take new configuration backup for volume group “uavg”.
[root@mylinz ~]# vgcfgbackup uavg Volume group "uavg" successfully backed up. [root@mylinz ~]#
2.You can find the new configuration file under the below mentioned location.
[root@mylinz ~]# cd /etc/lvm/
[root@mylinz lvm]# ls -lrt
total 36
-rw-r--r--. 1 root root 21744 Aug 18 2010 lvm.conf
drwx------. 2 root root 4096 Aug 12 23:57 archive
drwx------. 2 root root 4096 Aug 13 00:27 backup
drwx------. 2 root root 4096 Aug 13 00:27 cache
[root@mylinz lvm]# cd backup/
[root@mylinz backup]# ls -lrt
total 8
-rw-------. 1 root root 1474 Jun 3 2012 vg_mylinz
-rw-------. 1 root root 1164 Aug 13 00:27 uavg
[root@mylinz backup]# file uavg
uavg: ASCII text
[root@mylinz backup]#
[root@mylinz backup]# more uavg
# Generated by LVM2 version 2.02.72(2) (2010-07-28): Tue Aug 13 00:27:46 2013
contents = "Text Format Volume Group"
version = 1
description = "Created *after* executing 'vgcfgbackup /root/uavg.meta.bck uavg'"
creation_host = "mylinz" # Linux mylinz 2.6.32-71.el6.x86_64 #1 SMP Wed Sep 1 01:33:01 EDT 2010 x86_64
creation_time = 1376333866 # Tue Aug 13 00:27:46 2013
uavg {
id = "c87FyZ-5DND-oQ3n-iTh1-Vb1f-nBML-vUBUE9"
seqno = 10
status = ["RESIZEABLE", "READ", "WRITE"]
flags = []
extent_size = 8192 # 4 Megabytes
max_lv = 0
max_pv = 0
metadata_copies = 0
3.To restore the volume group meta data,you below command.
[root@mylinz ~]# vgcfgrestore uavg Restored volume group uavg [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
How to export/Move the volume group to other Linux node ?
Complete LVM volume group can be moved from one system to another system using vg commands.Here we will see step by step guide for this migration.
1.Unmount all the volumes from volume group which needs to be migrated.
2.Make the volume group inactive using “vgchange” command to ensure there will no I/O to the VG.
[root@mylinz ~]# vgchange -a n uavg 0 logical volume(s) in volume group "uavg" now active [root@mylinz ~]#
3.Export the volumegroup .
[root@mylinz ~]# vgexport uavg Volume group "uavg" successfully exported [root@mylinz ~]#
4.You can verify the exported status using “pvscan” command.
[root@mylinz ~]# pvscan PV /dev/sdd1 is in exported VG uavg [508.00 MiB / 456.00 MiB free] PV /dev/sda2 VG vg_mylinz lvm2 [19.51 GiB / 0 free] PV /dev/sde lvm2 [512.00 MiB] PV /dev/sdf lvm2 [5.00 GiB] Total: 4 [25.50 GiB] / in use: 2 [20.00 GiB] / in no VG: 2 [5.50 GiB] [root@mylinz ~]#
5.Now assign the disks from SAN level to the system where you want to import the volume group.
6.Scan the disks and make the disks available for VG import.
Check out the Disks or LUN scanning procedure in Redhat Linux.
7.Import the volume group.
[root@mylinz ~]# vgimport uavg Volume group "uavg" successfully imported [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree uavg 1 1 0 wz--n- 508.00m 456.00m vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
8.Activate the volume group for normal operation.
[root@mylinz ~]# vgchange -a y uavg 1 logical volume(s) in volume group "uavg" now active [root@mylinz ~]#
How to recreate the device files for LVM volumes ?
Due to server crash or other reason, we may loose the LVM device files and volume group directory . In those situation ,you need to recreate what you have lost. LVM provides command called “vgmknodes” which will help you to recreate those missing files.Here is a small experiment.
[root@mylinz ~]# cd /dev/mapper/ [root@mylinz mapper]# ls -lrt total 0 crw-rw----. 1 root root 10, 58 Aug 5 19:28 control lrwxrwxrwx. 1 root root 7 Aug 5 19:28 vg_mylinz-lv_root -> ../dm-0 lrwxrwxrwx. 1 root root 7 Aug 5 19:28 vg_mylinz-lv_swap -> ../dm-1 lrwxrwxrwx. 1 root root 7 Aug 13 00:47 uavg-ualvol1 -> ../dm-2 [root@mylinz mapper]# rm uavg-ualvol1 rm: remove symbolic link `uavg-ualvol1'? y [root@mylinz mapper]#
[root@mylinz etc]# mv lvm lvm.old [root@mylinz etc]# ls -lrt |grep lvm drwx------. 5 root root 4096 Jun 1 2012 lvm.old [root@mylinz etc]#
3.Let me run “vgmknodes” and see whether this command is able to recreate the removed device file and lvm directory .
[root@mylinz etc]# vgmknodes
4.Check whether devices files are created or not.
[root@mylinz mapper]# ls -lrt total 0 crw-rw----. 1 root root 10, 58 Aug 5 19:28 control lrwxrwxrwx. 1 root root 7 Aug 5 19:28 vg_mylinz-lv_root -> ../dm-0 lrwxrwxrwx. 1 root root 7 Aug 5 19:28 vg_mylinz-lv_swap -> ../dm-1 brw-rw----. 1 root disk 253, 2 Aug 13 00:54 uavg-ualvol1 [root@mylinz mapper]#
wow…its recreated.
5.Let me check /etc/lvm directory is created or not .
[root@mylinz etc]# ls -lrt |grep lvm drwx------. 5 root root 4096 Jun 1 2012 lvm.old drwxr-xr-x. 3 root root 4096 Aug 13 00:54 lvm [root@mylinz etc]#
Awesome…Its recreated.
How to remove the volume group ?
You can remove the volume group using vgremove command.
If any volumes from the volume group in mounted status ,you will get below error .
[root@mylinz ~]# vgremove uavg Do you really want to remove volume group "uavg" containing 1 logical volumes? [y/n]: y Can't remove open logical volume "ualvol1" [root@mylinz ~]#
Un-mount the volume and remove the volume group.
[root@mylinz ~]# vgremove uavg Do you really want to remove volume group "uavg" containing 1 logical volumes? [y/n]: y [root@mylinz ~]# [root@mylinz ~]# vgs VG #PV #LV #SN Attr VSize VFree vg_mylinz 1 2 0 wz--n- 19.51g 0 [root@mylinz ~]#
Hope this article shared enough information about LVM2 volume group administration.
You can also split and combine volume groups in LVM2 like veritas volume manager.
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