Docker Containers and Storage volumes

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When the default disk space allocated to a container is not appropriate for the job at hand, In these cases we need storage that can persist between container deployments.

In such case we use --mount or -v option.


Volumes are the preferred mechanism for persisting data generated by and used by Docker containers.

While bind mounts are dependent on the directory structure and OS of the host machine, volumes are completely managed by Docker.

Volumes have several advantages over bind mounts:

In addition, volumes are often a better choice than persisting data in a container’s writable layer, because a volume doesn’t increase the size of the containers using it, and the volume’s contents exist outside the lifecycle of a given container.

If your container generates non-persistent state data, consider using a tmpfs mount to avoid storing the data anywhere permanently, and to increase the container’s performance by avoiding writing into the container’s writable layer.

We can specify the volume by using --volume or -v option.

Bind mounts

docker container run --rm --it \
--mount=type=bind,target=/mnt/session_data,source=/data \
ubuntu:latest /bin/bash

You can read more about the bind mount here.

According to official website:

New users should use the --mount syntax. Experienced users may be more familiar with the -v or --volume syntax, but are encouraged to use --mount, because research has shown it to be easier to use.

  • If you use --mount to bind-mount a file or directory that does not yet exist on the Docker host, Docker does not automatically create it for you, but generates an error.
  • Use docker inspect <container_name> to verify that the bind mount was created correctly.
  • If you bind-mount a directory into a non-empty directory on the container, the directory’s existing contents are obscured by the bind mount. This can be beneficial, such as when you want to test a new version of your application without building a new image. However, it can also be surprising and this behavior differs from that of docker volumes.

By default bind-mount has read and write permission, but we can give the mount location read only access.

docker run -d \
  -it \
  --name devtest \
  --mount type=bind,source="$(pwd)"/target,target=/app,readonly \
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