🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: SUSE Linux Enterprise Server 16

📖 ~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

`df -h /` shows 100% used but `btrfs filesystem df /` indicates unallocated bytes remain.

Environment & Reproduction

Common on SLES 16 hosts that have run many zypper transactions over time.

Root Cause Analysis

Btrfs metadata chunks fill before data chunks, blocking new writes.

Quick Triage

Run `btrfs filesystem usage /` to see metadata vs data allocation.

Step-by-Step Diagnosis

Identify large snapshots via `snapper list` and `btrfs subvolume list /`.

Illustrative mockup for sles-16 — btrfs_root-full_terminal
Terminal diagnostics for Btrfs root filesystem reports full despite free disk space — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Run `btrfs balance start -dusage=50 -musage=50 /` during a maintenance window.

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Illustrative mockup for sles-16 — btrfs_root-full_logs
Logs and evidence for Btrfs root filesystem reports full despite free disk space — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Remove old kernel packages with `purge-kernels` to free metadata.

Verification & Acceptance Criteria

Post-balance `btrfs filesystem df /` shows reclaimed unallocated space.

Rollback Plan

Pause the balance with `btrfs balance cancel /` and re-evaluate if I/O suffers.

Prevention & Hardening

Schedule periodic `btrfs-balance.timer` units to keep metadata healthy.

Often triggers `transactional-update` failures and full Snapper queues.

Related tutorial: View the step-by-step tutorial for sles-16.

View all sles-16 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Btrfs storage administration on SLES 16 documentation.

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