📖 ~1 min read
Table of contents
Symptom & Impact
Install and upgrade operations fail with unmet dependencies, extending outage and patch lag.
Environment & Reproduction
Typical after reboot, power loss, or network failure during apt full-upgrade on Debian 9.
Root Cause Analysis
Partially configured packages and held versions create dependency chains apt cannot resolve automatically.
Quick Triage
Run package audit checks to identify the first broken package and held package list.
Step-by-Step Diagnosis
Review term logs and package state to confirm where dependency resolution first failed.
Solution – Primary Fix
Complete pending configuration and run fix-broken operations until package graph is consistent.
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Solution – Alternative Approaches
Temporarily remove conflicting packages and reinstall validated versions from stable repositories.
Verification & Acceptance Criteria
full-upgrade completes without unmet dependency messages and audit reports clean package state.
Rollback Plan
Pin previously stable versions or restore snapshot if repaired packages introduce regressions.
Prevention & Hardening
Avoid interrupting package transactions and standardize mirror reliability across environments.
Related Errors & Cross-Refs
Related to stale apt locks, third-party repo drift, and partial transaction rollbacks.
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 management recovery guides for apt and dpkg dependency repair.
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