Re: [tlug] Computer fails to boot

[Dave Brown <dagbrown@example.com>]

On Mon, Dec 29, 2008 at 03:56:56PM +0900, David Bernat wrote:
> I get a message stating
> 
> init: unable to execute "/bin/sh" for rc-default: Permission denied
> init: rc-default main process (****) terminated with status 255
> -------------------------------------------------------------
> **** refers to a four-digit numeral that varies at each reboot.
> 
> Is there a way to get back to a functioning system?

Heh.  I love it when stuff like that happens.  And by "love" I mean
"Everyone else, take cover until the flak guns stop."  Some fairly
colorful language can typically heard in situations like these.

You seem to have a working boot loader, only your /bin/sh is hosed.  If
you can't boot from a recovery CD (RECOMMENDED--see the other reply),
figure out your kernel's command line and append the following to it:

        init=/usr/bin/bash

Keep on trying until you find a shell that actually works.  Other
candidates might include /bin/bash, /usr/bin/sh, /usr/bin/ksh, /bin/ksh,
/bin/zsh, /usr/bin/zsh, or if you get really desperate, /bin/csh,
/bin/tcsh, and /usr/bin/tcsh .

If you're feeling REALLY technical-minded, you could try /usr/bin/python
or /usr/bin/irb as candidates for a shell (or if you're crazy,
/usr/bin/vim, /usr/bin/emacs, or /usr/bin/xemacs).

Basically what you need to do is get enough of a shell running to enable
you to restore /bin/sh to something useful.  As the other reply
mentioned, the standard /bin/sh is a symlink to, or a copy of,
/usr/bin/bash, with permissions 0755.

If your Linux system has an initrd, this can get infinitely more
entertaining.  One of the fun things about this exercise is that, if you
do it right, you will learn a LOT about what happens when a Linux system
boots up.

--Dave