====== Logical Volume Manager (LVM) Management ======

Logical Volume Manager (LVM) is used in Linux to abstract the filesystems away from the physical disk they sit on.

===== Mounting Volume Groups =====

Volumes can be grown online **BUT** cannot be reduced online. In order to reduce a volume group, the volume must be unmounted. For volumes containing the root file system, you need to boot using a live boot CD. Once the live CD is loaded, you can activate the Volume Groups by typing:
<code lang=bash>
vgchange -a y
</code>

===== Grow Volume =====

Check file system
<code lang=bash>
e2fsck -f /dev/vgNAME/lvNAME
</code>
Extend the logical volume. For example, to increase the file system from 15G to 20G:
<code lang=bash>
lvextend -L +5 /dev/vgNAME/lvNAME
</code>

ext3 file systems can be grown on-line.
<code lang=bash>
ext2online -v /dev/vgNAME/lvNAME
</code>
Others file systems will need to resized while the file system is unmounted.
<code lang=bash>
resize2fs -p /dev/vgNAME/lvNAME
</code>
Check file system
<code lang=bash>
e2fsck -f /dev/vgNAME/lvNAME
</code>


===== Reduce Volume =====

**REDUCE THE FILESYSTEM FIRST**

//If you reduce the size of the logical volume without first reducing the size of the file system, reduction will not work, since the file system will be incorrect after the volume is reduced.//

Check file system
<code lang=bash>
e2fsck -f /dev/vgNAME/lvNAME
</code>
Resize the file system. For example, resize the file system from 20G to 15G.
<code lang=bash>
resize2fs -p /dev/vgNAME/lvNAME 15G
</code>
Reduce the size of the logical Volume, in our example 20G to 15G is 5GB difference.
<code lang=bash>
lvreduce -L -5G /dev/vgNAME/lvNAME
</code>
Check file system again
<code lang=bash>
e2fsck -f /dev/vgNAME/lvNAME
</code>

===== Adding a New Disk =====

fdisk new disk and create primary partition of entire disk and set the partition type to be linux LVM (8e).
Add partition to LVM.
<code lang=bash>
pvcreate /dev/cciss/c1d2p1
</code>
Either create a new Volume group
<code lang=bash>
vgcreate vgNEWNAME /dev/cciss/c1d2p1
</code>
or extend an existing Volume Group
<code lang=bash>
vgextend vgNAME /dev/cciss/c1d2p1
</code>
Then, either create a new logical volume
<code lang=bash>
lvcreate -L 120G -n lvNEWNAME vgNAME
</code>
or use the "Grow Volume" to resize a logical volume to use the new drive.