Run levels

[Brian Fox]

Studying for the RHCE...

What's the difference between the "emergency" "single" and 1 runlevels?  I
purposefully clobbered my inittab file and rebooted.  Redhat prompted for a
runlevel.  Of the three, "single" was the only one that booted.

I'm curious why.  Grep'ing the words single and emergency in the etc
directory came up empty.  Those runlevels aren't explicitly supported by the
boot scripts.

Any insight greatly appreciated.

Thanks,
Brian