📖 ~1 min read
Table of contents
Symptom & Impact
Package installation fails with unmet dependencies and blocked upgrades.
Environment & Reproduction
Debian 9 hosts mix repository priorities and include held packages.
Root Cause Analysis
Version pin conflicts and partial upgrades create incompatible dependency graphs.
Quick Triage
List held packages and run dry resolver checks before forced changes.
Step-by-Step Diagnosis
Review apt policy output and dependency chains to isolate blockers.
Solution – Primary Fix
Align repositories, clear hold conflicts, and complete a consistent full upgrade.
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Solution – Alternative Approaches
Use temporary pin adjustments or targeted downgrades under change control.
Verification & Acceptance Criteria
No broken package state remains and installation paths complete successfully.
Rollback Plan
Reapply prior pin files and reinstall known good versions from cache.
Prevention & Hardening
Standardize repository definitions and validate upgrades in staging first.
Related Errors & Cross-Refs
Often appears alongside key trust failures and apt lock contention.
Related tutorial: View the step-by-step tutorial for debian-9.
View all debian-9 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian package pinning and apt resolver troubleshooting manuals.
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