Changing the default (bash) shell

One way of changing the default login shell, which happens to be the bash shell is as follows. You need to be an administrative user to do it.

sudo vi /etc/paswd

Find you user name in the above file and change the bash invocation on that line to another shell type.

Note that the csh or ksh is not installed by default in Ubuntu, so if you need those shells, you have to install them from the Ubuntu repository.