Docker Volumes, Mounting, and More

In Docker, whenever you create a container, there is a specified place where the data for the container will be stored. If you do not provide any location for that data to be stored, then it will be stored in the container. When you delete the container, the data will also be lost. However, when working on enterprise projects, to prevent data loss, you can remove a container but persist the data. You can use this data to create more containers and share the data between these containers. This is where Docker volume comes into play.

Features of Docker Volumes

• Sharing volume data and storage among multiple containers and host filesystems.
• Decoupling containers from storage.
• Does not delete contained data when deleting the container.
• Back up, restore, and migrate data easily.

In this tutorial, we will explain what a Docker volume is and how to use it, as well as how to mount a volume in Docker.

Requirements

• A system running Linux with Docker installed.
• A root password is configured.

Basic Syntax of Docker Volume

You can use the “docker volume” command to see all available options with volume:

You should see the following output after entering the above command:

Create a Volume

To create a data volume, you will first need to create a data volume on the Docker host and attach the volume to the container.

You can create a Docker volume using the command “docker volume create.” For example, use the following command to create a new Docker volume named myvolume:

You should see the following output:

You can list your existing volume using the following command:

You should see the following output:

If you want to see more information about volume, run the following command:

You should get the following output after running the above command:

Mount a Volume

At this point, you have one volume named myvolume. In this example, you will create a container and mount a myvolume to the container.

You can use the –mount option to mount the volume. The basic syntax to mount the volume to the container is shown below:

For example, to create a Ubuntu container and mount the myvolume to the container, run the following command:

This command will pull the Ubuntu image from the Docker Hub, start the container in interactive mode with the name volumecontainer, and mount the myvolume container to the /data inside the /data directory:

You can check the mounted volume with the following command:

You should see the data directory in the following output:

Now, we will create a sample file named file.txt inside /data directory with the following command:

Exit from the container with the following command:

Start the same container again with the following command:

Next, attach the running container with the following command:

Check whether your file.txt is persistent with the following:

You should get the following output after entering the above command:

This is a test file!

Share Data Between Containers

You can also share data between multiple containers using Docker volume.

As you know, we have created a volume named myvolume a new container named volumecontainer using this volume. We have also created a file named file.txt inside the volume.

Now, we will create another container named volumecontainer1 with the same myvolume volume using the following command:

Run the ls command, as shown below:

You should see the data directory in the following output:

Run the following command the check the file.txt:

You should see the same content that you created in the previous container:

This is a test file!

Mount Directory as a Volume

You can use the directory located inside your Docker host system as a volume and mount it to the container. You can also use the -v option to achieve the same, as shown below:

Create a directory named /data inside the Docker host with the following command:

Next, create some files inside the /Data directory:

Create a new container using the /Data directory as a volume with the following command:

This command will create a new container and mount the volume with the name /Data.

Run the following command to check the content of the /Data directory:

You should see all the files we have previously created in the host system, as shown below:

Remove Docker Volume

You can easily delete or remove the volume using the following syntax:

For example, to remove the volume named myvolume, run the following command:

You should get the following error:

This is because your volume is used by the container. So, you will need to stop and remove the container before removing the volume.

To stop and remove the container, run the following command:

Now, you can easily remove the volume.

Conclusion

In the above guide, you learned what Docker volume is, how to create it, and how to mount it inside the container. You also learned how to share data among multiple containers using the volume.