The ksu command, short for Kerberos Substitute User, is a powerful utility for Linux and Unix-like systems that allows users to switch their identity to another user using Kerberos authentication. This is particularly useful in environments where Kerberos is used for single sign-on and secure access management. It provides a secure alternative to the traditional su command by leveraging Kerberos tickets.

Understanding KSU Command Usage

The primary function of ksu is to facilitate secure user switching. Below are common usage patterns and their explanations:

Basic User Switching

To switch to another user using Kerberos authentication, you simply provide the target username:

# ksu [username]

This command will attempt to authenticate as the specified [username] using your current Kerberos credentials.

Specifying a Kerberos Ticket Cache

In scenarios where you need to use a specific Kerberos ticket cache, the -c option is employed:

# ksu -c [cache_name] [username]

Replace [cache_name] with the identifier of the desired ticket cache.

Executing Commands as Another User

You can also execute a specific command as another user without fully switching your interactive shell using the -e option:

# ksu [username] -e [command]

This is useful for running administrative tasks or specific scripts under a different user's privileges.

Advanced KSU Options

ksu offers several advanced options for more granular control over authentication and behavior:

Requesting Forwardable Tickets

The -F option allows you to request a forwardable Kerberos ticket on behalf of the target user:

# ksu -F [username]

Forwardable tickets are essential for services that require delegation of credentials.

Displaying Version Information

To check the version of the ksu utility installed on your system, use the -V flag:

# ksu -V

Verbose Mode

For detailed output and debugging information, enable verbose mode with the -v option:

# ksu -v [username]

Forcing Authentication Methods and Contexts

ksu provides options to force specific authentication methods or contexts:

• -o [option]: Force the use of a specific authentication option.
• -a [auth_context]: Specify a different authentication context.

# ksu -o [option] [username]
# ksu -a [auth_context] [username]

By understanding these commands and options, administrators and users can effectively leverage ksu for secure and efficient user identity management within Kerberized environments.

For more information on Kerberos and its related commands, consult the official documentation for your operating system and Kerberos implementation.