LVM commands tutorial : Part 3 : Logical Volume (lvextend, lvreduce, lvchange)

In this part, learn how to extend, reduce and change state of logical volume (lvextend, lvreduce, lvchange)

Logical volumes like VG can be extended and shrinked. We will be seeing lvextend, lvreduce, lvchange commands in this post.

Command : lvextend

To extend logical volume, you should have enough free space within that VG. Command syntex is pretty much similar to lvcreate command for size. Only thing is you need to supply final required size in command. For example current LV size is 1GB and you want to extend it with 2GB. Then you need to give final 3GB size in command argument.

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# lvextend -L 3072 /dev/vg01/lvol1

Logical volume "/dev/vg01/lvol1" has been successfully extended.

Volume Group configuration for /dev/vg01 has been saved in /etc/lvmconf/vg01.conf

Another important option is of mirror copies. It plays vital role in root disk mirroring. -m is the option with number of mirror copies as a argument.

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# lvextend -m 1 /dev/vg00/lvol1 /dev/disk/disk2_p2

The newly allocated mirrors are now being synchronized. This operation will

take some time. Please wait ....

Logical volume "/dev/vg00/lvol1" has been successfully extended.

Volume Group configuration for /dev/vg00 has been saved in /etc/lvmconf/vg00.conf

Command : lvreduce

This command used for decreasing number of mirror copies or decreasing size of LV. This is data destroying command. Hence make sure you have datat of related file system backed up first. The size and mirror copy options are works same for this command as well . -L for LE_reduce_size, -l number of LE to be reduces and -m is number of copies to be reduced.

Shell

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# lvreduce -L 500 /dev/vg01/lvol1

When a logical colume is reduced useful data might get lost;

do you really want the command to proceed (y/n) : y

Logical volume "/dev/vg01/lvol1" has been successfully reduced.

Volume Group configuration for /dev/vg01 has been saved in /etc/lvmconf/vg01.conf

While reducing mirror copies if one of the PV is failed or missing then command wont run successful. you need to supply -k option which will proceed to remove mirror in case PV is missing.

Command : lvchange

This command is used for changing characteristics of LV. There are numerous options which can be used.