chsh: "You may not change the shell for 'username'."

I'm trying to change the default shell for my user. But I keep getting this error:

$ chsh
You may not change the shell for 'flimm'.
$ chsh -s "$(which bash)"
You may not change the shell for 'flimm'.

I'm trying to understand why I may not change the shell for my user.

3 Answers

Since you confirmed that /usr/bin/chsh is setuid root (and therefore should allow non-privileged users to change their own login shell), the most likely explanation for this behavior is that either

• your current login shell was not in the /etc/shells file

or

• your current login shell was restricted (most likely /bin/rbash)

Ex.

$ grep fish /etc/shells || echo "invalid shell"
invalid shell
$
$ sudo chsh -s /usr/bin/fish testuser
$
$ su - testuser
Password:
Welcome to fish, the friendly interactive shell
testuser@t400s ~> chsh -s /bin/bash
You may not change the shell for 'testuser'.
testuser@t400s ~> exit

Note that there is no restriction on root setting a user's login shell to an invalid shell (as here), and doing so does not make an invalid shell valid by adding it to the /etc/shells file.

$ sudo chsh -s /bin/rbash testuser
$
$ su - testuser
Password:
testuser@t400s:~$
testuser@t400s:~$ chsh
You may not change the shell for 'testuser'.
testuser@t400s:~$ exit

If the target shell was absent from the /etc/shells file, you would have received a different message:

$ sudo chsh -s /bin/bash testuser
$
$ su - testuser
Password:
testuser@t400s:~$ chsh -s /usr/bin/fish
Password:
chsh: /usr/bin/fish is an invalid shell

You can try with command sudo usermod -s /bin/bash flimm

The user's login shell is kept in /etc/passwd, and is protected from modification by regular users. You can see it with getent passwd $USER.
If your new shell is listed in /etc/shells, you can change it with:

sudo chsh -s $(type -p bash) $USER

As with all manipulations of login info, be sure to have a login session on another terminal (Ctrl-Alt-F3) in case you break something and can't login.