How to use docker volume rm command to remove volumes

Introduction

In this lab, you will learn how to manage Docker volumes using the docker volume rm command. You will begin by creating a volume and then practice removing it.

Furthermore, you will explore scenarios where a volume is in use by a container and attempt to remove it, understanding the default behavior and how to force the removal of a volume that is currently attached to a running container.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL docker(("Docker")) -.-> docker/VolumeOperationsGroup(["Volume Operations"]) docker(("Docker")) -.-> docker/ContainerOperationsGroup(["Container Operations"]) docker/ContainerOperationsGroup -.-> docker/run("Run a Container") docker/ContainerOperationsGroup -.-> docker/ls("List Containers") docker/ContainerOperationsGroup -.-> docker/ps("List Running Containers") docker/ContainerOperationsGroup -.-> docker/rm("Remove Container") docker/ContainerOperationsGroup -.-> docker/inspect("Inspect Container") docker/ContainerOperationsGroup -.-> docker/create("Create Container") docker/VolumeOperationsGroup -.-> docker/volume("Manage Volumes") subgraph Lab Skills docker/run -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/ls -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/ps -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/rm -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/inspect -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/create -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} docker/volume -.-> lab-555262{{"How to use docker volume rm command to remove volumes"}} end

Create a volume

In this step, you will learn how to create a Docker volume. Volumes are the preferred way to persist data generated by and used by Docker containers. While bind mounts are dependent on the directory structure of the host machine, volumes are completely managed by Docker.

To create a volume, you use the docker volume create command followed by the name you want to give the volume. Let's create a volume named myvolume.

docker volume create myvolume

You should see the name of the volume printed to the console if the creation was successful.

Now, let's verify that the volume was created by listing all available volumes using the docker volume ls command.

docker volume ls

You should see myvolume listed in the output.

Attempt to remove the volume

In this step, you will attempt to remove the volume you created in the previous step. To remove a Docker volume, you use the docker volume rm command followed by the name of the volume.

Let's try to remove the myvolume volume.

docker volume rm myvolume

You should see the name of the volume printed to the console if the removal was successful.

Now, let's verify that the volume was removed by listing all available volumes again.

docker volume ls

You should no longer see myvolume in the output.

Remove the volume

In the previous step, you attempted to remove the volume. Now, let's ensure it is removed. You use the same command docker volume rm followed by the volume name.

docker volume rm myvolume

If the volume was successfully removed in the previous step, you might see an error indicating that the volume was not found. This is expected and confirms that the volume is gone. If the volume was not removed in the previous step, this command will remove it now.

To confirm the volume is removed, list the volumes again.

docker volume ls

The myvolume should not appear in the list.

Create a volume and a container using it

In this step, you will create a new volume and then create a Docker container that uses this volume to persist data.

First, let's create a new volume named mydata.

docker volume create mydata

Next, we will run a simple ubuntu container and mount the mydata volume to the /app directory inside the container. We will also run a command that writes some text to a file within the mounted volume.

Before running the container, let's pull the ubuntu image to ensure it's available locally.

docker pull ubuntu

Now, run the container and write to the volume:

docker run -d --name mycontainer -v mydata:/app ubuntu bash -c "echo 'Hello from the volume!' > /app/greeting.txt && tail -f /dev/null"

Let's break down this command:

docker run: Command to run a new container.
-d: Runs the container in detached mode (in the background).
--name mycontainer: Assigns the name mycontainer to the container.
-v mydata:/app: This is the volume mount. It mounts the Docker volume named mydata to the /app directory inside the container.
ubuntu: The Docker image to use.
bash -c "echo 'Hello from the volume!' > /app/greeting.txt && tail -f /dev/null": The command to run inside the container. It writes "Hello from the volume!" to a file named greeting.txt in the /app directory (which is the mounted volume) and then runs tail -f /dev/null to keep the container running.

To verify that the container is running and the volume is attached, you can inspect the container.

docker inspect mycontainer

Look for the "Mounts" section in the output. You should see an entry for the mydata volume mounted at /app.

Attempt to remove the volume in use

In this step, you will attempt to remove the mydata volume while it is still being used by the mycontainer container. This will demonstrate what happens when you try to remove a volume that is actively mounted to a running container.

Use the docker volume rm command to try and remove the mydata volume.

docker volume rm mydata

You should see an error message indicating that the volume is in use and cannot be removed. This is expected behavior. Docker prevents you from removing a volume that is currently attached to a running container to prevent data loss or unexpected behavior.

To confirm that the volume was not removed, list the volumes again.

docker volume ls

You should still see mydata in the output.

Force remove the volume in use

In the previous step, you learned that you cannot remove a volume that is currently in use by a running container. However, there might be situations where you need to remove a volume even if it's in use. Docker provides a way to force the removal of a volume using the -f or --force flag with the docker volume rm command.

Note: Forcing the removal of a volume that is in use can lead to data loss and unexpected behavior for the container using it. Use this option with caution.

Let's try to force remove the mydata volume while mycontainer is still running.

docker volume rm -f mydata

You should see the name of the volume printed to the console, indicating that it was removed.

Now, let's verify that the volume has been removed by listing the volumes.

docker volume ls

The mydata volume should no longer be in the list.

You can also check the status of the mycontainer.

docker ps

The mycontainer might still appear in the list of running containers, but it might be in an unhealthy state or stop unexpectedly because its volume has been removed.

Finally, let's stop and remove the container to clean up.

docker stop mycontainer
docker rm mycontainer

Summary

In this lab, you learned how to manage Docker volumes using the docker volume command. You started by creating a volume named myvolume using docker volume create and verified its existence with docker volume ls. You then practiced removing the volume using docker volume rm and confirmed its removal by listing volumes again.

You also explored the behavior of docker volume rm when a volume is in use by a container. You created a volume and a container that used it, and observed that attempting to remove the volume directly failed. Finally, you learned how to force the removal of a volume that is in use by adding the -f flag to the docker volume rm command.