A safe place to share everything about Docker. 8-O

====== Docker Cleanup Guide: Reclaiming Disk Space ======


Docker is an amazing technology that backs up each project I work on. Without diving too much into details, let's go through a workflow on how to clean up space that Docker takes up on your system.
===== 
Understanding Docker's Storage Model =====


The concept behind Docker is that it wants to cache every image it runs. An instance of a running image is a container, and they also use disk space. Finally, to persist data between container uptimes, Docker uses volumes to persist data on the host system.

==== Step 1: Understanding What Takes Space ====


The first step is always understanding what's consuming your disk space:

```bash
docker system df
```

This command shows you a high-level overview, but for detailed analysis, use:

```bash
docker system df -v
```

This verbose output breaks down Docker's storage into four key components:

===  1. Images - The Blueprint Cache ===


- **What they are:** Templates used to create containers
- **Why they accumulate:** Docker caches every image you pull or build
- **Space impact:** Often the largest consumer (can be 20-30GB+)
- **Reclaimable:** Unused images can be safely removed

=== 2. Containers - The Running Instances ===


- **What they are:** Actual running or stopped instances of images
- **Why they accumulate:** Stopped containers aren't automatically deleted
- **Space impact:** Usually minimal, but can add up
- **Reclaimable:** Stopped containers can be safely removed if you can recreate them

=== 3. Local Volumes - The Data Persistence Layer ===


- **What they are:** Persistent storage for container data
- **Why they accumulate:** Created for databases, config files, user data
- **Space impact:** Can be substantial, especially database volumes
- **Reclaimable:** ⚠️ **CAUTION** - Only remove if you're sure data isn't needed

=== 4. Build Cache - The Development Speedup ===


- **What it is:** Cached layers from building Docker images
- **Why it accumulates:** Each docker build creates cached layers
- **Space impact:** Can easily reach 15-20GB+ during active development
- **Reclaimable:** Safe to remove, but rebuilds will be slower



----
[[https://docs.portainer.io/user/docker/containers/stats|Checking the resource usage in Portainer]]
==== Step 2: Systematic Cleanup Workflow ====


===  Investigate Before You Delete ===


```bash
# List all images with sizes
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}"

# List all containers (running and stopped)
docker ps -a

# List all volumes
docker volume ls

# Check build cache details
docker buildx du
```

===  Safe Cleanup Commands ===


**Remove unused images (usually the biggest space saver):**
```bash
docker image prune -a  # Removes all unused images
```

**Remove stopped containers:**
```bash
docker container prune  # Removes all stopped containers
# Or selectively: docker rm [container_id] [container_id]
```

**Remove unused volumes (⚠️ BE CAREFUL - this deletes data):**
```bash
docker volume prune  # Only removes truly unused volumes
# Or selectively: docker volume rm [volume_name]
```

**Remove build cache:**
```bash
docker builder prune -a  # Safe to remove, just slows future builds
```

====  The Nuclear Option ====


If you want to reclaim maximum space and start fresh:

```bash
docker system prune -a --volumes
```

> ⚠️ **Warning:** This removes everything unused - images, containers, volumes, networks, and build cache.

=====  Step 3: Sustainable Cleanup Strategy =====


Rather than the "delete everything and hope it's fine" approach, I recommend this workflow:

1. **Weekly maintenance:** Run `docker system df -v` to monitor growth
2. **Monthly cleanup:** Remove unused images and build cache
3. **Project completion:** Clean up project-specific volumes and images
4. **Before major updates:** Full cleanup to start with a clean slate

## Pro Tips for Long-term Management
 
  * **Use .dockerignore:** Reduces image sizes and build cache bloat
  * **Multi-stage builds:** Keep final images lean
  * **Regular pruning:** Don't let cache accumulate to 50GB+ before cleaning
  * **Volume data:** Backup important container data separately

---

Happy coding, and may your Docker storage never exceed your SSD capacity! 🐳

> **Remember:** The goal isn't to delete everything, but to maintain a balance between performance (caching) and disk usage. Clean regularly, but thoughtfully.