boot linux in safe mode

How do I boot a linux box in safe mode?

Thank You.

Which distro? Some of them install a Grub boot menu with a "safe mode" for each installed kernel.

Red hat 4

Grub boot runlevel 3 is what I found in Google -- still depends on your boot loader etc but if you can't get that to work, tell us more. (In particular, do you have Grub, and what does its default entry look like.)

Yes, I do have grub. I already got it. Thanks.