ODOC: About chsh command
Enables a user to change their login shell.
chsh [-s login_shell] [user]
-s -> login_shell Enables a user to specify the login shell.
Used without the -s option enables the user to specify the path of their shell.
chsh will accept the full pathname of any executable file on the system. However, it will issue a warning if the shell is not listed in the /etc/shells file. On the other hand, it can also be configured such that it will only accept shells listed in this file, unless you are root.