Well buddy, these cmds will just use remaining free space of your hdd, they ain't going to screw any data of your HDD

pvcreate cmd make your hda/sda partition eligible for adding in volume group and vgextend just adds that partition in volume group and extends its total available space. Then you know what to do, just resize your partition cause you'll have free space available in your volume group then. :-)

Unless you solve the problem that filled the /var, extending it won't solve the problem for long.
You need to backup & delete some logfiles and either fix the process that's causing the problem or alter the logrotate settings (or both).

Hello:

Just go back to my post. Instead of using /dev/hdb1, you are going to use /dev/sda5. That is the only difference. Also, I would also follow chrism01 advice. Otherwise, we will go back to square one. Check any crontab jobs that my be running or just create a crontab job to weekly remove file log files bigger than 2GB or a size of your choosing.

A script that I use to delete log files bigger thatn 2.5GB is as follows:

All of this is assuming that /dev/sda5 is a free partition.
Remember to backup your data. If you follow all the instructions, you are going to be safe, but backups do not hurt. Believe me, you can run the command by accident.
I hope this helps you.