Su: must be suid to work properly

To use the “su” command properly, the user must have the necessary permissions or be logged in as the root user. The “su” command, short for “substitute user”, allows users to switch to another user account in the current shell or terminal session.

Here is the basic syntax of the “su” command:

      su [option] [username]
   

The “su” command without any options or username usually switches to the root user if the user provides the correct password. However, when using the “su” command, certain considerations and examples should be kept in mind:

1. Specifying a username: If a specific username is provided, the “su” command will switch to that user’s account. For example, to switch to the user “john”, you would use the command “su john”. If no username is specified, it defaults to the root user.
2. Using the dash option: Adding a dash (-) after the “su” command, such as “su -“, initializes environment variables and simulates a complete login. This is useful for running commands as another user with a fresh environment. For instance, “su – john” would switch to the user “john” with a new session.
3. Running a command as another user: It is also possible to run a single command as another user without switching the entire session. The “-c” option is used for this purpose. For example, “su john -c ‘ls -l'” would execute the “ls -l” command as the user “john”.
4. Providing the root password: If executing the “su” command without specifying a username and prompted for a password, it usually expects the root password. Only users with the necessary permissions can switch to the root account.