Docker Volumes

Docker volumes let you save data used by your containers, so it doesn’t disappear when the container stops or is removed. Think of it as a way to keep your important files safe and share them across containers.

Why Use Docker Volumes?

1. Keep Data Safe: Save your container’s data even after it stops.
2. Share Data: Let multiple containers use the same data.
3. Better Speed: Volumes are faster than other ways of sharing files.
4. Easy Backups: You can back up your data easily from volumes.

Types of Docker Volumes

1. Anonymous Volumes: Created automatically by Docker. These don’t have names and are harder to manage.
2. Named Volumes: You create these with a name and can reuse them in multiple containers.
3. Bind Mounts: Link a folder on your computer to a folder inside the container. They’re flexible but less isolated.

Hands-On: Using Docker Volumes with MySQL

Step 1: Get the MySQL Image

Download the MySQL image:

docker pull mysql:latest        

Step 2: Create a Volume

Create a named volume to store MySQL’s data:

docker volume create mysql-data        

Check if it’s created:

docker volume ls        

You should see mysql-data in the list.

Step 3: Start the MySQL Container

Run the MySQL container and use the volume:

docker run -d  --name mysql-container -e MYSQL_ROOT_PASSWORD=password -v mysql-data:/var/lib/mysql mysql:latest        

What this does:

• -d: Runs the container in the background.
• --name: Gives the container a name (mysql-container).
• -e MYSQL_ROOT_PASSWORD=password: Sets the MySQL root password to password.
• -v mysql-data:/var/lib/mysql: Uses the mysql-data volume to store database files.

Check if It’s Running

docker ps        

You should see mysql-container in the list.

Step 4: Access MySQL

Enter the MySQL shell:

docker exec -it mysql-container mysql -u root -p        

Type the password (password) when asked.

show databases ;        

Displays all the databases created.

create database demo ;        

Creates a Database "demo".

exit        

Exits the interactive terminal.

Step 5: Stop and Remove the Container

Stop the container:

docker stop mysql-container        

Remove the container:

docker rm mysql-container        

Step 6: Check Data Persistence

Run a new container with the same volume:

docker run -d  --name mysql-container -e MYSQL_ROOT_PASSWORD=password -v mysql-data:/var/lib/mysql mysql:latest        

The data from the old container will still be there, showing that volumes save your data.