This how-to was completed on Debian, but the method should be the same for other OS's.
1. First you need to download a couple of files:
a. http://radium.hexxeh.net/quake3.zip (3.1 Mb)
b. http://www.andershizzle.com/Q3%20Demo%20Paks.zip (69 Mb)
To do this change to the directory you want to download them to:
To do this simply use 'unzip'
unzip Q3\ Demo\ Paks.zip
To do this we use 'mv'
mv baseq3/pak* quake3/baseq3/
This is done using 'chmod'
chmod +x quake3/start.sh
chmod +x quake3/ioquake3.arm
chmod +x quake3/ioq3ded.arm
First we need to change the current directory to the directory that contains start.sh
Then we need to run start.sh
6. ALL DONE! If you were doing this via SSH, then you will only see this: