What's the Ubuntu's default shell?
In some distributions you do not have the bash shell. But you can enable that using the procedure below:
1) Check if 'bash' is available
2) If not, (you encounter an command not found error) install that:
$ pkg_add -r -v bash
3) Change the default shell to bash of any user:
$ chsh -s /bin/bash username
4) To check for the bash installation location, you can type:
$ which bash
You can refer my blog, for more information.