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Docker Volume

Docker Volume

In general, Docker containers are ephemeral, running just as long as it takes for the command issued in the container to complete. By default, any data created inside the container is ONLY available from within the container and only while the container is running.

Docker volumes can be used to share files between a host system and the Docker container.

Bindmounting a Volume

We can use -v flag in docker run to bind mount a volume. Let’s take a look at an example, which will create a directory called nginxlogs in your current user’s home directory and bindmount it to /var/log/nginx in the container:

docker run --name=nginx -d -v ~/nginxlogs:/var/log/nginx -p 5000:80 nginx

-v ~/nginxlogs:/var/log/nginx sets up a bindmount volume that links the /var/log/nginx directory from inside the Nginx container to the ~/nginxlogs directory on the host machine. Docker uses a : to split the host’s path from the container path, and the host path always comes first.

If the first argument of -v begins with a / or ~/, you’re creating a bindmount. Remove that, and you’re naming the volume.

  • -v /path:/path/in/container mounts the host directory, /path at the /path/in/container
  • -v path:/path/in/container creates a volume named path with no relationship to the host.

If you make any changes to the ~/nginxlogs folder, you’ll be able to see them from inside the Docker container in real time as well. In other words, the content of ~/nginxlogs and /var/log/nginx are synchronous.

Reference