How to increase filesystem size in RHEL v5.8?

Question

Below is the partial output from the df -h command. Notice /var is setup as its own filesystem but has reached 100% of its 2GB size.

How can I increase the size of the /dev/mapper/rootVG-var file system? There is definitely much more space available on the physical disk itself. This is Redhat release 5.8.

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/rootVG-slash

                  2.0G  977M  876M  53% /

/dev/mapper/rootVG-home

                  9.7G  2.7G  6.6G  29% /home

/dev/mapper/rootVG-opt

                  9.7G  1.2G  8.1G  13% /opt

/dev/mapper/rootVG-tmp

                  3.4G   53M  3.2G   2% /tmp

/dev/mapper/rootVG-var
                  2.0G  1.9G     0 100% /var

Solution

Questioner was able to solve this with the following commands:

1. Extend the size of the underlying volume lvextend -L10G /dev/mapper/rootVG-var
2. Resize the filesystem to the new size of the underlying volume resize2fs /dev/mapper/rootVG-var

_{Originally posted as a comment by dabayl. Stealing in these situations is explicitly allowed and encouraged on SE sites.}