How to use the command 'runcon' (with examples)

The runcon command is used to run a program in a different SELinux security context. It allows users to specify the domain, role, and user context to run a command with. This can be useful for testing or troubleshooting SELinux policies.

Use case 1: Determine the current domain

Code:

runcon

Motivation:

Determining the current domain can be helpful when troubleshooting issues related to SELinux policy enforcement. By knowing the current domain, users can understand which security context is being used by default.

Explanation:

The runcon command without any arguments is used to print the current security context. It will display the current domain, role, and user context.

Example output:

system_u:system_r:unconfined_service_t:s0

Use case 2: Specify the domain to run a command in

Code:

runcon -t domain_t command

Motivation:

In certain cases, users may need to run a command with a specific SELinux domain. This is useful when testing or evaluating the behavior of a command or program under a different security context.

Explanation:

In this use case, the -t option is used to specify the domain to run the command with. The domain_t argument should be replaced with the actual domain name. The command argument should be replaced with the desired command to run.

Example output:

Running 'command' in domain 'domain_t'...

Use case 3: Specify the context role to run a command with

Code:

runcon -r role_r command

Motivation:

Running a command with a specific context role can be necessary to test the behavior of a program or command in different roles. This can help identify any permissions or access issues related to SELinux role-based access control.

Explanation:

In this use case, the -r option is used to specify the context role to run the command with. The role_r argument should be replaced with the actual role name. The command argument should be replaced with the desired command to run.

Example output:

Running 'command' with role 'role_r'...

Use case 4: Specify the full context to run a command with

Code:

runcon user_u:role_r:domain_t command

Motivation:

Specifying the full SELinux context can be necessary in certain cases, especially if users need to mimic a specific SELinux user, role, and domain combination.

Explanation:

In this use case, the full SELinux context is specified using the format user_u:role_r:domain_t. The user_u, role_r, and domain_t arguments should be replaced with the actual user, role, and domain names respectively. The command argument should be replaced with the desired command to run.

Example output:

Running 'command' with context 'user_u:role_r:domain_t'...

Conclusion:

The runcon command is a versatile tool for running programs in different SELinux security contexts. Whether you need to determine the current domain, specify a specific domain, role, or the full context, runcon provides the necessary functionality. By understanding and utilizing the different use cases, users can effectively test and troubleshoot SELinux policies.