Ubuntu 18.04 LTS – Common Problem 002 – Diagnosis and Fix

📖 ~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

apt reports unmet dependencies and refuses to install or upgrade target packages.

Environment & Reproduction

Ubuntu 18.04 systems with mixed repositories, held packages, or partial upgrades. Triggered by sudo apt install .

Root Cause Analysis

Package version constraints cannot be satisfied from enabled repositories, or local holds pin incompatible versions.

Quick Triage

Run apt-cache policy , apt-mark showhold, and sudo apt –fix-broken install to detect immediate blockers.

Step-by-Step Diagnosis

Inspect /etc/apt/sources.list and /etc/apt/sources.list.d/*.list for unsupported PPAs or wrong release codenames.

Solution – Primary Fix

Disable conflicting repositories, clear holds if appropriate, run sudo apt update, then sudo apt -f install and retry installation.

Solution – Alternative Approaches

Use aptitude resolver suggestions, or explicitly install compatible versions using apt install package=version.

Verification & Acceptance Criteria

apt install/upgrade completes successfully and apt check returns no dependency errors.

Rollback Plan

Restore original repository files and package holds from backup if newer package set causes regressions.

Prevention & Hardening

Avoid mixing many PPAs, review pins in /etc/apt/preferences.d, and keep repository sources minimal and trusted.

Related Errors & Cross-Refs

Depends: but it is not going to be installed, held broken packages, and version conflict messages.

Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.

View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

man apt-cache, man apt-mark, and Ubuntu package pinning documentation.