Docker volume path linux

Docker: where is docker volume located for this compose file

I was setting up some materials for a trainning, when I came around this sample compose file: https://github.com/dockersamples/example-voting-app/blob/master/docker-compose.yml and I couldn’t find out how this volume is mounted, on lines 48 and 49 of the file:

Can someone explain me where is this volume on the host? Couldn’t find it and I wouldn’t like to keep any postgresql data dangling around after the containers are gone. Similar thing happens to the networks:

networks: front-tier: back-tier: 

2 Answers 2

Finding the volumes

Volumes like this are internal to Docker and stored in the Docker store (which is usually all under /var/lib/docker ). You can get a list of volumes:

$ docker volume ls DRIVER VOLUME NAME local 1c59d5b7e90e9173ca30a7fcb6b9183c3f5a37bd2505ca78ad77cf4062bd0465 local 2f13b0cec834a0250845b9dcb2bce548f7c7f35ed9cdaa7d5990bf896e952d02 local a3d54ec4582c3c7ad5a6172e1d4eed38cfb3e7d97df6d524a3edd544dc455917 local e6c389d80768356cdefd6c04f6b384057e9fe2835d6e1d3792691b887d767724 

You can find out exactly where the volume is stored on your system if you want to:

$ docker inspect 1c59d5b7e90e9173ca30a7fcb6b9183c3f5a37bd2505ca78ad77cf4062bd0465 [ < "Driver": "local", "Labels": null, "Mountpoint": "/var/lib/docker/volumes/1c59d5b7e90e9173ca30a7fcb6b9183c3f5a37bd2505ca78ad77cf4062bd0465/_data", "Name": "1c59d5b7e90e9173ca30a7fcb6b9183c3f5a37bd2505ca78ad77cf4062bd0465", "Options": <>, "Scope": "local" > ] 

Cleaning up unused volumes

As far as just ensuring that things are not left dangling, you can use the prune commands, in this case docker volume prune . That will give you this output, and you choose whether to continue pruning or not.

$ docker volume prune WARNING! This will remove all volumes not used by at least one container. Are you sure you want to continue? [y/N] 

«Empty» definitions in docker-compose.yml

There is a tendency to accept these «empty» definitions for things like volumes and networks when you don’t need to do anything other than define that a volume or network should exist. That is, if you want to create it, but are okay with the default settings, then there is no particular reason to specify the parameters.

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Docker Volumes: How to Create & Get Started

Docker volumes are widely used and useful tools for ensuring data persistence while working in containers. They are a better alternative than compiling additional writable layers, which increase Docker image size.

In this tutorial, learn how to use Docker Volumes with practical examples.

What are Docker Volumes?

Docker volumes are file systems mounted on Docker containers to preserve data generated by the running container.

The volumes are stored on the host, independent of the container life cycle. This allows users to back up data and share file systems between containers easily.

Getting Started With Docker Volumes

There are different ways to mount a Docker volume while launching a container. Users can decide between the -v and the —mount flags, which are added to the docker run command.

This article shows examples of both flags in use.

How to Create a Docker Volume

To create a Docker Volume use the command:

docker volume create [volume_name]

Docker automatically creates a directory for the volume on the host under the /var/lib/docker/volume/ path. You can now mount this volume on a container, ensuring data persistence and data sharing among multiple containers.

For example, to create a volume under the name data, you would run the command:

docker volume create data

List Docker Volumes

To verify you have successfully created a Docker volume, prompt Docker to list all available volumes with:

The output displays a list of volumes, specifying their location (DRIVER) and their VOLUME NAME. In the image below, you can see the volume data created in the previous section.

Inspecting Docker Volumes

To see more information about a Docker volume, use the inspect command:

docker volume inspect [volume_name]

It lists details of a volume, including its location on the host file (Mountpoint). Everything stored within the data volume can also be found in the directory listed under the mountpoint path.

Mounting a Data Volume

To mount a data volume to a container add the —mount flag to the docker run command. It adds the volume to the specified container, where it stores the data produced inside the virtual environment.

To run a container and mount a data volume to it, follow the basic syntax:

docker run --mount source=[volume_name],destination=[path_in_container] [docker_image]

Replace [path_in_container] with the path where you want to place the data volume in the container. Everything stored in that directory automatically gets saved on the data volume on the host as well.

For example, to launch an Ubuntu container and mount the data volume to it, run:

docker run -it --name=example1 --mount source=data,destination=/data ubuntu

The command instructs Docker to run a container in interactive mode ( -it ) from the Ubuntu image, under the name example1 , while mounting the volume data in the /data directory inside the container.

Then, check to verify the volume was successfully mounted by listing the content of the container:

Find the Docker volume under the name defined while launching the container. In this example, it is data.

Copying Files Between Containers From a Shared Volume

Let’s see how Docker volumes allow you to share files between containers.

To do so, we use the volume and container created in the previous section. This included running the commands:

• docker volume create data
• docker run -it —name=example1 —mount source=data,destination=/data ubuntu

1. Once you have switched to the container command prompt, move to the data volume directory:

2. Create an empty sample file using the touch command:

4. Then, launch a new container example2 with the same data volume:

docker run -it --name=example2 --mount source=data,destination=/data ubuntu

5. List the content of the container. You should find the data directory, as in example1:

6. Move to the data directory and list the content of it:

The output should list the sample1.txt file you created in the previous container (example1).

Note: You might be interested in finding out how Kubernetes persistent volumes work.

Mounting a Host Directory as a Data volume

You can also mount an existing directory from the host machine to a container. This type of volume is called Host Volumes.

You can mount host volumes by using the -v flag and specifying the name of the host directory.

Everything within the host directory is then available in the container. What’s more, all the data generated inside the container and placed in the data volume is safely stored on the host directory.

The basic syntax for mounting a host directory is:

docker run -v "$(pwd)":[volume_name] [docker_image]

The «$(pwd)» attribute instructs Docker to mount the directory the user is currently in.

The following example outlines how this is done.

1. First, create a sample directory on the host under the name tmp and move into it:

2. Once inside the directory, create a test file to see whether it will be available from the container:

2. Then, use the docker run command to launch an Ubuntu container with the host directory attached to it:

docker run -it -v "$(pwd)":/data1 ubuntu

This launches the container in interactive mode and mounts a volume under the name data1.

3. List the content of the container and verify there is a data1 directory:

4. Open the mounted directory and list the content. The output should display the file you created on the host:

Volume Permission and Ownership

Volume permissions van be changed by configuring the ownership within the Dockerfile.

Use the RUN instruction and the chown command to set the Docker volume permission. Make sure this instruction precedes the line defining the VOLUME .

Alternatively, you can change the ownership of the directory used as the host volume.

For instructions on how to use the chown command, refer to Linux File Permission Tutorial: How To Check And Change Permissions.

How to Delete Docker Volumes

To delete a Docker volume, you need to specify its name.

The basic syntax for removing a Docker volume in the command line is:

docker volume rm [volume_name]

Docker removes volumes only if they are not in use at the moment. If there is a container with the specified volume, it responds with an error. To proceed, stop and remove the container and then rerun the docker volume rm command.

Note: If you don’t know the name of the volume, use the docker volume ls command.

How to Delete All Volumes at Once

To delete all unused Docker volumes with a single command:

The output warns you it will remove all local volumes not used by at least one container. Press y to continue.

After reading this article, you should have a better understanding of how Docker volumes work, as well as how to mount volumes to containers.

Sofija Simic is an experienced Technical Writer. Alongside her educational background in teaching and writing, she has had a lifelong passion for information technology. She is committed to unscrambling confusing IT concepts and streamlining intricate software installations.

Docker images can easily become too large to handle, which is why it is important to keep their size.

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Where docker volumes are located?

Need to know where docker volumes are located when using the docker machine on macOS. The installation is using boot2docker, so the VM works behind. Example:

docker volume create test-data 

5 Answers 5

It’s inside the virtual machine and isn’t directly accessible from the host.

Debug-level commands like docker volume inspect will give you a path, but they really are only for emergency debugging and not for routine use. If you have a way to get a shell in the VM you can see that path, but you really shouldn’t be directly accessing files there, and you shouldn’t be routinely docker inspect ing anything.

macOS use a virtual machine it’s different to linux where you can access to volumes from /var/lib/docker/volumes. For macOS you should connect to a VM to find your volumes.

If you use persistent data volumes in Docker, and you want to access them with command-line.

If your docker host is Linux, that’s not a problem; you can find Docker volumes by /var/lib/docker/volumes path.

However, that’s not the case when you use Docker for Mac. Try to cd /var/lib/docker/volumes from your MacOS terminal, you ‘ll get nothing.

You see, your Mac machine isn’t a real Docker host. Docker for Mac runs a virtual machine and hides it from you to make things simple.

So, to access persistent volumes created by Docker for Mac, you need to connect on that VM.

In order to accomplish this, we need to use a serial terminal on Mac. There’s a terminal application called “screen” that’s going to help us.

We need to “screen into” the Docker driver by executing a command:

1. screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty
2. You should see a blank screen, just press Enter , and after a while, you should see a command line prompt
3. Now you’re inside Docker’s VM and you can cd into volumes dir by typing: cd /var/lib/docker/volumes

If you need to transfer files from your MacOS host into Docker host you can refer to File Sharing

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