In MkLinux, hit "s" instead of enter at the bootloader dialog (the
one with the countdown).

In linux-ppc, set boot-file to "/vmlinux 1" in the Boot Variables
program in MacOS, or using the command:
   nvsetenv boot-file " /vmlinux 1"
as root in linux.

It is one of the oddest single user modes I've seen - it seems to go
multiuser, displaying a login prompt + everything, then dropping down to
a root prompt, with all filesystems mounted RW.

slipcon@cs.jhu.edu