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Disk Cleanup — Ubuntu System Cleanup Guide

Last reviewed: 2026-05-29

Purpose: Step-by-step guide for identifying and reclaiming disk space on Ubuntu systems, focusing on Docker container artifacts and KVM/libvirt virtual machine storage.

Overview

This folder contains a single comprehensive Markdown guide (UbuntuDiskCleanUp.md, 4 KB) that covers the complete workflow for diagnosing disk space issues and recovering storage on Ubuntu servers — particularly those running Docker containers and KVM/libvirt virtual machines.

Contents

File Description
UbuntuDiskCleanUp.md Full disk cleanup guide with commands and strategies

Topics Covered

1. Disk Usage Identification

  • du -h / --max-depth=1 for top-level analysis
  • Deep-dive into /var and /var/lib directories

2. Docker Cleanup

  • docker system prune -a -f to remove unused images, containers, and volumes
  • Truncating container log files to reclaim space
  • Configuring Docker log rotation (daemon.json with max-size: 100m, max-file: 3)

3. KVM/libvirt Management

  • Identifying VM disk usage with virsh list --all and qemu-img info
  • Deleting unused VMs with virsh undefine --remove-all-storage
  • Compacting qcow2 disk images via zero-fill and qemu-img convert
  • Finding orphaned disk images no longer attached to any VM

4. System Logs & Cache

  • journalctl --vacuum-time=7d / --vacuum-size=500M
  • apt clean to clear apt cache
  • Snap package revision cleanup

5. Tools & Quick Script

  • ncdu interactive disk analyzer recommendation
  • One-liner quick cleanup script for routine maintenance

Key Takeaway

The biggest disk gains come from deleting unused VMs, cleaning inside running VMs, and pruning Docker — not from logs, which are rarely the issue at TB scale.