Ubuntu 16.04 LTS sudo command fails due to corrupted /etc/sudoers

📖 ~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

Privilege escalation is unavailable, preventing incident response and routine system administration.

Environment & Reproduction

Occurs after manual edits, merge conflicts, or malformed include files.

Root Cause Analysis

Syntax or permission errors in sudoers policy cause parser failure and command rejection.

Quick Triage

Use root console or recovery shell to inspect sudoers without invoking broken sudo path.

Step-by-Step Diagnosis

Validate main sudoers file and included fragments for syntax and mode integrity.

Solution – Primary Fix

Repair malformed entries with visudo and set strict permissions on policy files.

Solution – Alternative Approaches

Restore known-good sudoers from configuration management backup.

Verification & Acceptance Criteria

sudo commands execute successfully and policy checks pass for required admin roles.

Rollback Plan

Boot recovery and restore previous file snapshot if corrected policy still blocks access.

Prevention & Hardening

Manage sudoers declaratively and enforce syntax validation in deployment pipelines.

Related Errors & Cross-Refs

parse error in /etc/sudoers near line, no valid sudoers sources found.

Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.

View all Ubuntu 16.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

sudoers best practices for secure operations on Ubuntu 16.04.