🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: Ubuntu 26.04 LTS

📖 ~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

Upgrades stall because dependency resolution cannot produce a valid install plan.

Environment & Reproduction

Frequently happens when mixed repositories or held packages exist.

sudo apt full-upgrade

Root Cause Analysis

Version pinning, held packages, or stale indexes create incompatible package constraints.

Quick Triage

List held packages and inspect candidate versions.

apt-mark showhold && apt policy

Step-by-Step Diagnosis

Trace conflict chain for failing packages and check origin priorities.

sudo apt -o Debug::pkgProblemResolver=yes dist-upgrade
Illustrative mockup for ubuntu-26-04-lts — unmet_dependencies
APT unmet dependencies output — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Unhold blocking packages, repair broken state, and retry with consistent repositories.

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sudo apt-mark unhold  && sudo apt --fix-broken install && sudo apt full-upgrade
Illustrative mockup for ubuntu-26-04-lts — apt_fix_broken
Fixing broken package dependencies — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Temporarily remove conflicting packages and reinstall from supported Ubuntu repositories.

Verification & Acceptance Criteria

`apt full-upgrade` completes with no unresolved dependency errors.

Rollback Plan

Reapply package holds and revert repository list changes if upgrade path proves unstable.

Prevention & Hardening

Standardize apt source policies and review holds before each maintenance cycle.

Related to phased updates, mixed PPAs, and partial release upgrade remnants.

Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.

View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu package dependency management and release upgrade best practices.

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