How to Access Docker Volumes and images in Ubuntu

Access Docker Volumes

Docker volumes are stored in the default directory /var/lib/docker/volumes.

1. List Docker Volumes
   To view all Docker volumes, use:

   docker volume ls
   

2. Access Volume Files
   • Navigate to the volume directory:

     cd /var/lib/docker/volumes
     

   • Inside, each volume has its own folder where data is stored. For example:

     ls /var/lib/docker/volumes/<volume-name>/_data
     

     The _data directory contains the actual files for that volume.

3. Edit or Inspect Data Use standard Linux commands like ls, cat, nano, or vi to view or edit files.
4. Backup a Volume Use tar to back up a volume:

   docker run --rm -v <volume-name>:/volume -v $(pwd):/backup ubuntu tar czf /backup/volume-backup.tar.gz -C /volume .
   

Access Docker Images

Docker images are also stored in /var/lib/docker.

1. List Docker Images
   To list all images on your system, use:

   docker images
   

2. Access Image Layers Docker stores images in layers within /var/lib/docker. To inspect these:
   • Navigate to the image storage directory:

     cd /var/lib/docker
     

   • Specific subdirectories (like overlay2 or aufs) hold the layers and metadata for images.
3. Extract or Analyze an Image Use docker save to export an image for analysis:

   docker save -o image.tar <image-name>
   

   Then extract it:

   tar -xvf image.tar
   

Grant Non-root Access to Docker Data

By default, only the root user or users in the docker group have permission to access Docker files.

1. Add Your User to the Docker Group
   If not already added:

   sudo usermod -aG docker $USER
   

   Log out and log back in for the change to take effect.

2. Access Files as Root
   If necessary, use sudo to access Docker directories:

   sudo ls /var/lib/docker
   

3. Change Permissions (Optional)
   If you need broader access:

   sudo chmod -R 755 /var/lib/docker
   

   Be cautious when modifying permissions, as it could compromise security.

Manage and Clean Up Volumes and Images

1. Remove Unused Volumes:

   docker volume prune
   

2. Remove Unused Images:

   docker image prune
   

Let me know if you need detailed help with a specific part!