Scenario: In the Dom0 (Host) you have an LVM Logical Volume that you export to the DomU (Guest) and it appears as a hard drive partition which you want to make larger.

Example- Dom0: /dev/VolGroup00/LogVol00 -> DomU: /dev/xvda1

Resizing an LVM Logical Volume used as a DomU partition

When you use an LVM Logical Volume as a DomU partition it will show up in the DomU as /dev/xvda1 as apposed to /dev/xvda. The line in the DomU config file will look something like this.

disk = ['phy:vgsys/lvvirt,xvda1,w']

Get the Logical Volume name and path

So you gave your Xen virtual machine a 10GB Logical Volume and not it's not enough eh? This is easy to fix.

We start by using the lvdisplay command to get the path to the Logical Volume

[ root@vs /srv/xen ] lvdisplay
--- Logical volume ---
LV Name                /dev/vgsys/lvvirt
VG Name                vgsys
LV UUID                XMWzWW-oZih-A5uH-91Sa-7l1y-8cqf-18KcNB
LV Write Access        read/write
LV Status              available
# open                 1
LV Size                60.00 GB
Current LE             1920
Segments               2
Allocation             inherit
Read ahead sectors     auto
- currently set to     256
Block device           253:2

According to lvdisplay the path to our Logical Volume is /dev/vgsys/lvvirt.

Resizing Logical Volume

Resizing the Logical Volume is actually very easy, you'll be amazed.

lvresize --size +10G /dev/vgsys/lvvirt

This lvresize command specifies to add 10GB to /dev/vgsys/lvvirt. This will only take a second.

Resizing the filesystem

resize2fs /dev/mapper/vgsys-lvvirt

That's really it! You can only hot resize if the Filesystem is getting larger. If you need to shrink it then you'll have to take the Volume offline first. Isn't this easier than dealing with partitions that are too small?

Note: The procedure listed above can be done on the fly (as in while the system is running).