How to mount a directory inside a docker container

Question

This question already has answers here:

Mount directory in Container and share with Host (3 answers)

Closed 2 years ago.

I would like to mount a directory from a docker container to the local filesystem. the directory is a website root and I need to be able to edit it my local machine using any editor.

I know I can run docker run -v local_path:container_path but doing that it is only creating an empty directory inside the container.

How can one mount a directory inside a docker container on linux host?

Answer 1

If your goal is to provide a ready to go LAMP, you should use the VOLUMES declaration inside the Dockerfile. VOLUME volume_path_in_container The problem is that docker will not mount the file cause they were already present in the path you are creating the volume on. You can go as @Grif-fin said in his comment or modify the entry point of the container so he copy the file you want to expose to the volume at the run time.

You have to insert your datas using the build COPY or ADD command in Dockerfile so the base files will be present in the container.

Then create an entrypoint that will copy file from the COPY path to the volume path.

Then run the container using the -v tag and like -v local_path:volume_path_in_container. Like this, you should have the files inside the container mounted on the local. (At least, it was what I add).

Find an exemple here : https://github.com/titouanfreville/Docker/tree/master/ready_to_go_lamp.

It will avoid to have to build every time and you can provide it from a definitive image.

To be nicer, it would be nice to add an user support so you are owner of the mounted files (if you are not root).

Hope it was useful to you.

Answer 2

It is a bit weird but you can use named volumes for that. Despite host mounted volumes, named ones won't be empied. And you can access the dir. See the example:

docker volume create --name data
docker run -rm=true -v data:/etc ubuntu:trusty
docker volume inspect data

[
    {
        "Name": "data",
        "Driver": "local",
        "Mountpoint": "/var/lib/docker/volumes/data/_data",
        "Labels": {},
        "Scope": "local"
    }
]

See the mount point?

mkdir ~/data
sudo -s
cp -r /var/lib/docker/volumes/data/_data/* ~/data
echo "Hello World">~/data/hello.txt

docker run --rm=true -v ~/data:/etc ubuntu:trusty cat /etc/fstab  #The content is preserved
docker run --rm=true -v ~/data:/etc ubuntu:trusty cat /etc/hello.txt  #And your changes too

It is not exactly you were asking for but depends on your needs it works

Regards