π ~1 min read
Table of contents
Symptom & Impact
dist-upgrade fails and security patching is delayed by unresolved package dependency chains.
Environment & Reproduction
Frequently triggered by mixed repositories, package holds, or partial prior upgrades.
Root Cause Analysis
apt resolver cannot satisfy constraints because installed and candidate versions conflict.
Quick Triage
List held packages, inspect broken dependencies, and check repository priorities.
Step-by-Step Diagnosis
Run simulated upgrades and capture dependency conflict output for precise remediation.

Solution – Primary Fix
Release problematic holds, repair package state, and retry a clean dist-upgrade.
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Solution – Alternative Approaches
Disable third-party repositories temporarily to isolate and resolve conflict sources.
Verification & Acceptance Criteria
Upgrade simulation and live execution complete with no held-broken or unmet dependency errors.
Rollback Plan
Revert repository files and package holds to the previous known-good configuration.
Prevention & Hardening
Review repo governance and pinning strategy before scheduled upgrade cycles.
Related Errors & Cross-Refs
Related errors include unmet dependencies and package kept back after dist-upgrade.
Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.
View all Ubuntu 16.04 LTS tutorials on the Tutorials Hub β
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
See Ubuntu package resolver docs and Debian packaging dependency guidelines.
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