I tried to change my user's shell, but used "sudo chsh", and changed the root shell to "bash" instead of "/bin/bash". Now when I try to change it I get "chsh: PAM authentication failed" and it seems like other things aren't working, either.
~$ sudo su
Cannot execute bash: No such file or directory
This happens with recovery mode, too. What do I do to change it to something usable?
If you are able to login using your regular user, just change the root users shell directly:
sudo gedit /etc/passwd
Find the line for you root user, usually the first one, and change the last part from
...:bash
to
...:/bin/bash
And you should be good to go.
(NB: Replace gedit with whatever editor you fancy.)
Use the Ubuntu install disk to boot the live session.
Mount the root ('/') partition on the harddisk (make sure it's writable).
edit '[HD mount point]/etc/passwd' (eg /media/sda1/etc/passwd),
root should be the first line, just correct the login shell which will be the last entry on the line.
Unmount harddisk. Remove CD. Reboot
I played with this once ages ago:
cd /bin ; sudo su
What's happening is without a / in front the shell is being interpreted as a relative path. Oh gee if we are in /bin it resolves correctly.
If you get really stuck; the rescue CD is the long way around. The boot option init=/bin/sh gives you a root shell immediately. The cursor just blinks at you with no prompt but you have a root shell. Do
set -i
# mount / -o remmount,rw
# vi /etc/passwd
<fix it>
# mount / -o remount,ro
# reboot -f
Note, as a short-term work-around, you can use the "-s" switch on the su command to specify a shell. For example:
su -s /bin/bash
would start your su session with the /bin/bash shell. Same goes for sudo su -s /bin/bash (or whatever shell you'd like) @Bjarke Freund-Hansen's answer is the permanent fix.
