Lost Root Password
This was a post by Paul Brook to the mailing list when we discussed accessing system files on a Kubuntu box without root or su access.
For the record, this is how to (re)set a root password without using a live cd: Addinit=/bin/sh
to your kernel commandline. If you're using grub then pressing "e" will allow you to temporarily edit a menu item. This should get you to a shell, bypassing all the init scripts, including the ones that ask for a password ;-) At this point you probably can't change anything because the root filesystem will still be mounted readonly. To fix this do:
mount -o remount,rw /
If it's on a separate partition you probably also need to mount /usr: Most Ubuntu systems probably put everything on a single partition, so you can skip this. Technically /usr/bin isn't essential, it just has useful things like vim and passwd. Without it you may have to resort to editing files with sed.
You should then be able to reset the root password, either by typing "passwd",or by hacking /etc/shadow.