Series of the tutorial to learn LVM commands. In this part, learn how to create, delete the logical volume and view details of it (lvcreate, lvdisplay, lvremove)
This is the last part of the LVM commands tutorial. Previously we have seen physical volume, volume group commands which can be seen on below links :
- Part 1 : Physical Volume (pvcreate, pvdisplay)
- Part 1 : Physical Volume (pvchange, pvmove)
- Part 2 : Volume group (vgcreate, vgdisplay, vgscan)
- Part 2 : Volume group (vgextend, vgreduce, vgexport, vgimport)
- Part 2 : Volume group (vgcfgbackup, vgcfgrestore, vgchange)
- Part 2 : Volume group (vgremove, vgsync)
- Part 3 : Logical Volume (lvcreate, lvdisplay, lvremove)
- Part 3 : Logical Volume (lvextend, lvreduce, lvchange)
- Part 3 : Logical Volume (lvsync, lvlnboot)
Logical volumes are small slices carved out of physical volumes storage space which is collectively available in the volume group. For more details check LVM legends.
This command used to create a new logical volume. Logical volumes are mounted on directories as a mount point. So logical volume size is the size you want for the mount point. Use a command like below :
# lvcreate -L 1024 /dev/vg01 Logical volume "/dev/vg01/lvol1" has been successfully created with character device "/dev/vg01/rlvol1" Volume Group configuration for /dev/vg01 has been saved in /etc/lvmconf/vg01.conf
In the above command, you need to supply size in MB (1 GB in the above example) to
-L argument and volume group name in which you need to create that LV. If no name suggested in command then by default command creates LV with name
/dev/vg01/lvolX (X is next available number).
This command supports below options –
-lNumber of LEs
Created LV details can be seen using command
We have seen above how to create LV, now we will see how to view details of it. This command is the same as pvdisplay for PV and vgdisplay for VG. It shows you details like name, volume group it belongs to, size, permission, status, allocation policy, etc.
# lvdisplay /dev/vg01/lvol1 --- Logical volumes --- LV Name /dev/vg01/lvol1 VG Name /dev/vg01 LV Permission read/write LV Status available/syncd Mirror copies 0 Consistency Recovery MWC Schedule parallel LV Size (Mbytes) 1024 Current LE 32 Allocated PE 32 Stripes 0 Stripe Size (Kbytes) 0 Bad block on Allocation strict IO Timeout (Seconds) default
More detailed output can be obtained with
-v option. In this detailed output, you can get the LE details where they reside and LV distribution across disks.
# lvdisplay -v /dev/vg01/lvol1 --- Logical volumes --- LV Name /dev/vg01/lvol1 VG Name /dev/vg01 ----- Output clipped ---- --- Distribution of logical volume --- PV Name LE on PV PE on PV /dev/disk/disk22 32 32 --- Logical extents --- LE PV1 PE1 Status 1 00000 /dev/disk/disk22 00000 current 00001 /dev/disk/disk22 00001 current 00002 /dev/disk/disk22 00002 current 00003 /dev/disk/disk22 00003 current 00004 /dev/disk/disk22 00004 current 00005 /dev/disk/disk22 00005 current 00006 /dev/disk/disk22 00006 current 00007 /dev/disk/disk22 00007 current 00008 /dev/disk/disk22 00008 current 00009 /dev/disk/disk22 00009 current 00010 /dev/disk/disk22 00010 current 00011 /dev/disk/disk22 00011 current 00012 /dev/disk/disk22 00012 current 00013 /dev/disk/disk22 00013 current 00014 /dev/disk/disk22 00014 current ----- output truncated -----
Removing a logical volume is data destroying task. Make sure you take the backup of data within the mount point then empty it and stop all user/app access to it. If LV is not empty then the command will prompt you for confirmation to proceed.
# lvremove /dev/vg01/lvol1 The logical volume "/dev/vg01/lvol1" is not empty; do you really want to delete the logical volume (y/n) : y Logical volume "/dev/vg01/lvol1" has been successfully removed. Volume Group configuration for /dev/vg03 has been saved in /etc/lvmconf/vg01.conf
Once lvol is deleted its number is again available for next new lvol which is being created in the same VG. All PE assigned to this LV will be released as free PE and hence free space in VG will increase.
We will be seeing how to extend and reduce LV also how to activate or deactivate LV in the next post.
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