Description of problem:
arch/x86_64/kernel/head64.c appends ` console=tty0' to the kernel
command line if there isn't a `console=' string in there.  If your
grub command line doesn't specify console=tty0, and you just append
`init=/bin/bash' to the command line, you won't get a shell prompt,
because console=tty is going to be passed to bash.

Version-Release number of selected component (if applicable):
kernel-2.6.8-1.624

How reproducible:
Every time

Steps to Reproduce:
1.cat /proc/cmdline
2.reboot and append init=/bin/bash to the command line
  
Actual results:
1. shows the command line ends with console=tty0, that isn't specified
in the grub boot command line.  2. fails because bash doesn't like the
argument it is passed.

Expected results:
The extraneous argument should probably not be shown, and it would be
nice if 2. worked regardless of the presence of console= in the
default boot command line.

Additional info:
Adding `console=tty0 init=/bin/bash' works.