Introduction to SELinux

Security-Enhanced Linux (SELinux) is a security architecture for Linux systems that allows users to define access controls and enforce security policies. It operates on a principle of least privilege, ensuring that users and processes have the minimum level of access necessary to perform their tasks.

SELinux enhances system security by:

• Preventing unauthorized access to files and processes.
• Isolating applications to limit the effects of vulnerabilities.
• Providing a flexible mechanism to enforce security policies.

SELinux operates in three modes:

1. Enforcing: SELinux policy is enforced, and access is denied based on the defined policies.
2. Permissive: SELinux policy is not enforced, but violations are logged for monitoring.
3. Disabled: SELinux is turned off completely.

To manage SELinux policies, you can use the following commands:

# Check current SELinux status
sestatus

# Change SELinux mode
setenforce 1  # Set to Enforcing
setenforce 0  # Set to Permissive

# List all SELinux policies
semodule -l

To effectively utilize SELinux, consider these best practices:

• Regularly audit and review your SELinux logs.
• Use the audit2allow tool to create policies based on logged denials.
• Ensure your software is compatible with SELinux policies.
• Test configuration changes in a sandbox environment before production deployment.