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Systems & Data Center · Intermediate

Security-Enhanced Linux (SELinux)

A Linux kernel mandatory access control system that confines processes using security labels and policy.

Definition

SELinux enforces policy rules on top of standard discretionary permissions, so a compromised service is limited to the files and ports its type is allowed. RHEL uses targeted policy by default, confining network-facing daemons. Denials are logged to /var/log/audit/audit.log as AVC messages.

Example

httpd cannot serve files labeled user_home_t until they are relabeled httpd_sys_content_t.

Exam tip

When a service fails with correct file permissions on RHEL, suspect SELinux labels and check the audit log, rather than disabling SELinux.

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