Can I change the default shell?

Yes, you can change the default shell for the user. To change joker's default shell to bash, you can use the following command:

sudo usermod -s /bin/bash joker

After running this command, you can verify the change with:

sudo grep -w 'joker' /etc/passwd

You should see /bin/bash at the end of joker's entry, indicating that the default shell has been changed.