How to Store Docker Images and Containers on an External SSD in macOS

If you’re using Docker on a Mac with limited internal storage, you may want to store your Docker images and containers on an external SSD. By default, Docker saves all generated images and containers in your system’s internal disk, which can quickly fill up your space. This guide explains how to move Docker storage to an external SSD.

Option 1: Using a Symlink (Recommended for Simplicity)

This method involves moving Docker’s storage folder to an external SSD and creating a symbolic link.

Steps:

1. Quit Docker Desktop: Open Terminal and ensure Docker is not running:

   docker ps  # Check if containers are running
   docker stop $(docker ps -q)  # Stop running containers

Then, completely quit Docker Desktop.

2. Move Docker’s Storage Folder to the External SSD:

   mv ~/Library/Containers/com.docker.docker /Volumes/ExternalSSD/

(Replace /Volumes/ExternalSSD with the actual path of your SSD.)

3. Create a Symlink:

   ln -s /Volumes/ExternalSSD/com.docker.docker ~/Library/Containers/com.docker.docker

4. Restart Docker Desktop and verify that everything works correctly.

Option 2: Changing Docker Data Root (For CLI Users)

If you use Docker without Docker Desktop and manage it through the command line, you can configure Docker to store data in a different location.

Steps:

1. Create a New Storage Location on the SSD:

   sudo mkdir -p /Volumes/ExternalSSD/docker-data

2. Edit Docker’s Daemon Configuration:

   sudo nano /etc/docker/daemon.json

3. Modify or Add the Following Configuration:

   {
     "data-root": "/Volumes/ExternalSSD/docker-data"
   }

4. Restart Docker:

   sudo systemctl restart docker

Option 3: Changing Docker Desktop Preferences (If Available)

Some versions of Docker Desktop allow changing the disk image location directly through the UI.

Steps:

1. Open Docker Desktop.
2. Go to Settings > Resources > Advanced.
3. Locate the disk image location setting and select your external SSD.
4. Apply changes and restart Docker Desktop.

Verifying the Change

To confirm that Docker is using the new storage location, run:

docker info | grep "Docker Root Dir"

This should display the new path on your external SSD.

Conclusion

Moving Docker’s storage to an external SSD is a great way to free up space on your Mac while maintaining performance. Choose the method that best fits your setup, and enjoy a more optimized development environment!