Switch User with the Su Command

The su command (short for "substitute user" or "switch user") is a fundamental utility in Unix-like operating systems, including Linux. It allows a user to execute commands with the privileges of another user, most commonly the superuser (root). This is essential for performing administrative tasks that require elevated permissions.

Basic Su Command Usage

To switch to another user account, you typically use the following syntax:

su <username>

If you omit the <username>, the su command defaults to switching to the root user. You will be prompted to enter the password for the target user.

Executing Commands as Root

A common use case is to temporarily gain root privileges to run a specific command. You can do this by using the - or -l (login) option, which simulates a full login for the target user, setting up their environment variables:

su - -c "<command>"

For example, to update package lists as root:

su - -c "apt update"

Understanding Su vs. Sudo

While su is powerful, the sudo command is often preferred for executing commands with elevated privileges. sudo allows administrators to grant specific users the ability to run certain commands as root (or another user) without sharing the root password. This provides better security and auditing capabilities.

Key Su Command Options

• - or -l: Simulate a full login, setting up the target user's environment.
• -c <command>: Execute a single command and then exit.
• -s <shell>: Specify the shell to use.

Further Resources

• su(1) - Linux man page
• GNU Coreutils Manual - id (related to user identification)
• Understanding the Linux su Command