How to run in failsafe mode?

[mrk]

I run out of disc space on hard drive. Linux won't completely start up, I can't see login screen.

-How do I get into failsafe mode (before the loginscreen opens)?
-How to boot from CD? Where do I setup BIOS?
-Any other way to get some files from Linux partition?

I'm using YDL 301 on PPC G3