SELinux Prevents Custom Service from Binding Non-Standard Port

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Service starts and exits immediately or refuses socket bind, making endpoint unavailable to clients.

Environment & Reproduction

Happens after moving service from default port to custom listener during migration or security segmentation.

Root Cause Analysis

SELinux type for the daemon domain does not allow binding the selected TCP/UDP port label.

Quick Triage

Check `systemctl status `, `ss -tulpen`, and AVC records; avoid disabling SELinux for quick workarounds.

Step-by-Step Diagnosis

Use `semanage port -l`, map expected domain, and inspect `journalctl -u ` plus audit denials.

Solution – Primary Fix

Add port mapping with `semanage port -a/-m`, restart service, and keep SELinux in enforcing mode.

Solution – Alternative Approaches

Use default service port type where possible or define scoped custom policy module for strict environments.

Verification & Acceptance Criteria

Listener binds successfully, remote clients connect, and no recurring AVC denials appear.

Rollback Plan

Remove custom port mapping and revert service port to known working standard assignment.

Prevention & Hardening

Document approved service ports and include SELinux port mapping checks in deployment CI/CD.

Related Errors & Cross-Refs

`semanage port -l | grep && journalctl -u -n 100`

Related tutorial: View the step-by-step tutorial for rhel-7.

View all rhel-7 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

SELinux policy management references for RHEL 7 and service domain port type administration.