Locked out of machine - please help

[Nicolas Kovacs]

Le 29/09/2011 18:21, richardkimber at btinternet.com a écrit :
> While adding a user to a group (in a new installation), via the KDE
> settings panel, the process seemed to go OK in the gui, but I found that
> the new group was not listed on the command line by the 'groups'
> command. When I tried to logout I got a message saying that policykit
> had crashed, and I then found that I could not log back in. I tried
> maintenance mode but couldn't get access.
>
> I booted up a rescue session and set up passwords for both user and
> root, but neither was accepted by the system.  I just can't get access
> to the machine at all.
>
> Is there anything I can do, short of re-installing?  It's taken me
> two and a half days to do the install and set everything up :-( so I'd
> like to be able avoid doing that again. Is there perhaps a package that
> could be re-installed in the rescue session that might solve it?
>
> - Richard
>

On machines running GRUB 0.97 (and with a root account), there was a 
nice trick. On boot, edit the kernel line and add the following boot 
parameter:

init=/bin/bash

Then when you get a login prompt, do this:

# mount -o remount,rw /

Then do what you have to do, for example:

# passwd

Problem: no init was started, so how to shutdown the machine? Here goes:

# mount -o remount,ro /

And then simply hit the Poweroff button :o)

I'm regularly training folks on RHEL servers, and more often than not, 
the students forget their root passwords (ts, ts...). This is a way to 
restore things when they shot themselves in the foot.

Unfortunately, a) I don't know how to do this with GRUB2 (which I hate 
with a passion), and b) no root account in a default Ubuntu install 
(which is the first thing I restore).

Cheers,

Niki Kovacs
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