Final answer:
The default login shell can be changed by a user with the command 'chsh'. 'chmod' is used for changing file permissions and 'rmsh' does not pertain to changing the login shell.
Step-by-step explanation:
A user can change the default login shell by using the command chsh (change shell). The chsh command allows a user to change their default shell in Unix and Unix-like operating systems. To change the shell, the user typically enters chsh followed by various options and the full path to the new shell. The chmod command changes file permissions and is not related to changing the log-in shell, while rmsh is not a standard command for changing the shell.