chsh

What is chsh?

chsh, short for “change shell,” is a command-line utility that allows you to modify the default login shell for a user account. The login shell is the program executed when a user logs in. Different shells offer varying functionalities and customization options. Common shells include Bash (Bourne Again Shell), Zsh (Z Shell), and Fish (Friendly Interactive Shell). Changing a user’s shell can impact their environment, available commands, and overall user experience.

Using chsh

The basic syntax for chsh is straightforward:

chsh [options] [username]

• chsh: The command itself.
• [options]: Optional arguments to modify command behavior. We’ll look at these later.
• [username]: The username of the account you want to modify. If omitted, it defaults to the currently logged-in user.

Changing your own shell:

To change your own login shell to Bash, you would simply run:

chsh -s /bin/bash

This command uses the -s option to specify the new shell path. /bin/bash is the standard path for Bash. You will be prompted to enter your password for confirmation.

Changing another user’s shell (requires root privileges):

To change another user’s shell, you need root privileges (or sudo access). Let’s say you want to change user john’s shell to Zsh:

sudo chsh -s /bin/zsh john

This command utilizes sudo to execute the command with root privileges. Remember to replace /bin/zsh with the appropriate path for the desired shell. Note that the user john won’t be prompted for a password; only the root (or sudoer) will be.

Common chsh Options

While -s is the most frequently used option, chsh offers a few others:

• -s <shell>: Specifies the new shell path. This is the most important option.
• -l or --list: Lists the available shells for the user. This is useful for seeing which shells are installed and available for selection.
• --help or -h: Displays help information about the command.

Example using -l:

chsh -l

This command will list all the available shells for the currently logged in user.

Example using --help:

chsh --help

This will provide detailed information about the command’s usage and options.

Finding Shell Paths

To ensure you use the correct path for your desired shell, you can typically find them in the /bin or /usr/bin directories. You can use the which command to find the exact path:

which bash
which zsh
which fish

This will output the full path to each shell if it’s installed on your system. Using the which command helps prevent typos and ensures you’re using the correct path when specifying the -s option with chsh.

Permissions and Security

Remember that changing another user’s shell requires appropriate privileges. Improper use of chsh can compromise system security. Always exercise caution and only grant shell changes to users who legitimately require them. Regularly review user accounts and their associated shells to maintain a secure system.