Creating and mounting volumes

Creating a new volume can be performed explicitly using the docker volume create command. It is also possible to create named and anonymous volumes automatically when the container starts. To manually create a Docker named volume, follow these steps:

1. Execute the following command:

docker volume create <volumeName>

2. After creation, you can inspect the details of the volume using the docker volume inspect command:

As you can see, the volume data is stored as a regular directory in the host filesystem when using the default local driver.

To mount a volume to a container, you have to use the --mount or --volume (short parameter: -v) parameters for the docker run command. Originally, --volume was used for stand-alone containers, whereas --mount was used for swarm containers, but starting with Docker 17.06, --mount can also be used for standalone containers and is the recommended practice as it provides more robust options. More about these flags can be found in the official documentation: https://docs.docker.com/storage/volumes/#choose-the--v-or---mount-flag.

Follow these steps to learn how to mount a volume:

1. Assuming that you would like to mount test-named-volume from the previous example in a new PowerShell container under the C:\Data directory, you have to specify the --mount parameter, as follows:

docker run -it --rm `
           --isolation=process `
           --mount source=test-named-volume,target=C:\Data `
           mcr.microsoft.com/powershell:windowsservercore-1903

2. After the container has started and the terminal has been attached, try creating a simple file in the directory where a volume has been mounted:

echo "Hello, Volume!" > C:\Data\test.txt

3. Now, exit the container (which will cause it to stop and be automatically removed due to the --rm flag) and inspect the volume directory on the host:

PS C:\WINDOWS\system32> cat C:\ProgramData\Docker\volumes\test-named-volume\_data\test.txt
Hello, Volume!

4. To demonstrate that the named volume can be easily mounted in another container, let's create a new container based on the mcr.microsoft.com/windows/servercore:1903 image and with a volume mount target that's different from the one in the previous example:

docker run -it --rm `
           --isolation=process `
           --mount source=test-named-volume,target=C:\ServerData `
           mcr.microsoft.com/windows/servercore:1903

5. If you inspect the volume directory in the container, you will notice that the test.txt file is present and contains the expected content:

C:\>more C:\ServerData\test.txt
Hello, Volume!

In the next subsection, we'll take a quick look at how to remove volumes using the Docker CLI.