Shells and Shell Startup Files
A Linux shell is a program that actually finds and executes the commands you type in your terminal window. All shells depend on startup files in your home directory to set up your shell environment - the way in which your shell behaves. When your account was created, you were given several default startup files: .cshrc, .exrc, .kshrc, .login, and .profile. Do not change your startup files unless you are sure you know what you are doing. Whenever you do change any of your startup files, be sure to save a copy of the old file first, so that you can go back to it if your changes don't work.
The CLAS Linux Group team now allows users to change their shell (see /etc/shells for valid shells). Below is an example where the user, when prompted to enter a new shell, entered /bin/zsh:
WARNING: The /bin/zsh shell is not supported by Linux Support. If you use it as your login shell, you will have to troubleshoot any problems with the shell on your own.
Do you still want to make /bin/zsh your new shell? (y/n)