I've got Ubuntu Hoary. I compiled Quasar from source and created a deb file using checkinstall and then installed it with dpkg. It did not work so I uninstalled it with Synaptic. For some wierd reason all my user account are gone now. I cannot login into my Ubuntu, because firstly, gdm does not start, complaining about gdm.config and secondly, when I have eventually console, it rejects any user name/login.

I've taken a look at /etc booting from knoppix and did not find any passwd file there, though I've got passwd.lock.

I've got a feeling that it happened because Quasar creates a user named Quasar when installed. I think what might happen was that it removed all users for some reason instead of only this Quasar.

I really need help because I cannot do anything at my PC now, Windows is killing me. I guess I have to restore users in some way but have no idea how to do it.

There's probably a package that contains a 'base' configuration for passwd, then you could re-add any actual user accounts that you have added. Or, you could just restore from backups: you did make a backup, right?

I tried to install base package and add new users but it failed and it does not allow to add users without installing a base package.

I've got the following message when try to boot:

basically I need to find a way to add a user...

and you're right, I've not got a backup, silly me....

Is there a backup passwd file? It's often called '/etc/passwd-'

Nothing. I really do not know what happened.

One advice was to boot from live or recovery cd and chroot into existing install and then create users from their. However, I do not know what happened to all other ssytem users and groups.

I have not tried it yet, will do when back home.

Well I have done the following:

1. Installed Ubuntu on my second HD
2. Set up users as they were on my main installation
3. Copied the following files from a new /etc to an old /etc:
group
gshadow
passwd
shadow
sudoers
4. Edited menu.lst to add option to boot my old installation

And pretty much that's it. I had to change ownership of users homes, because they were messed up.

Now it works. Hopefully it will be fine.

The only question left is how to point grub to my old menu.list again, because it now uses menu.list from a second HD?

I generally use lilo, so I'm of little help there, sorry. But I'm glad your main problem was able to be resolved.