To set bash as the default shell for a user on a Linux or Unix system, you can use the chsh command.
For example, to set bash as the default shell for the current user, you can use the following command:
chsh -s /bin/bash
This will set the default shell for the current user to bash.
To set the default shell for a different user, you can use the -u option followed by the username. For example:
chsh -s /bin/bash -u username
This will set the default shell for the user username to bash.
It's important to note that you may need to have root privileges to use the chsh command to change the default shell for other users.
For more information about using the chsh command, you can refer to the chsh manual page or use the --help option. For example:
man chsh
chsh --help
It's also important to note that you may need to log out and log back in for the changes to take effect.