🐳 Docker Data Directory Migration to `/app`

This document captures the exact commands used to move Docker’s data directory from /var/lib/docker to /app/docker, along with concise explanations for each step.

🎯 Objective

Move Docker storage to a larger partition:

From: /var/lib/docker (limited space)
To: /app/docker (400GB available)

🔍 1. Verify Docker Status

docker ps

Lists running containers to confirm Docker activity.

systemctl status docker

Checks whether the Docker service is running and healthy.

🔍 2. Verify Current Docker Root Directory (Before Change)

docker info | grep "Docker Root Dir"

Checks the current Docker data directory to confirm where Docker is storing data before migration.

⚙️ 3. Inspect Existing Configuration

ll /etc/docker/

Lists Docker configuration directory.

cat /etc/docker/daemon.json

Displays current Docker configuration (if present).

⛔ 4. Stop Docker Service

sudo systemctl stop docker

Stops Docker to safely modify its data directory.

📁 5. Create New Data Directory

sudo mkdir -p /app

Creates the target directory for Docker storage.

sudo chown -R root:root /app

Ensures correct ownership and permissions.

🔄 6. Copy Existing Docker Data

sudo cp -rf /var/lib/docker /app/

Copies all existing Docker data (images, containers, volumes) to the new location.

🔎 7. Validate Copied Data

ll /app/docker/

Checks copied data in the new directory.

📝 8. Configure Docker to Use New Path

cat > /etc/docker/daemon.json

{
  "data-root": "/app/docker"
}

✅ 9. Final Configuration:

cat /etc/docker/daemon.json

{
  "data-root": "/app/docker"
}

▶️ 10. Move Older configuration to backup folder

sudo mv /var/lib/docker /var/lib/docker.bak

Restarts Docker with the new configuration.

▶️ 11. Start Docker Service

sudo systemctl start docker