How to mount a host directory in a Docker container

Question

I am trying to mount a host directory into a Docker container so that any updates done on the host is reflected into the Docker containers.

Where am I doing somethin

Answer 1

Is it possible that you use docker on OS X via boot2docker or something similar.

I've made the same experience - the command is correct but nothing (sensible) is mounted in the container, anyway.

As it turns out - it's already explained in the docker documentation. When you type docker run -v /var/logs/on/host:/var/logs/in/container ... then /var/logs/on/host is actually mapped from the boot2docker VM-image, not your Mac.

You'll have to pipe the shared folder through your VM to your actual host (the Mac in my case).

Answer 2

On Mac OS, to mount a folder /Users/<name>/projects/ on your mac at the root of your container:

docker run -it -v /Users/<name>/projects/:/projects <container_name> bash

ls /projects

Answer 3

As of Docker 18-CE, you can use docker run -v /src/path:/container/path to do 2-way binding of a host folder.

There is a major catch here though if you're working with Windows 10/WSL and have Docker-CE for Windows as your host and then docker-ce client tools in WSL. WSL knows about the entire / filesystem while your Windows host only knows about your drives. Inside WSL, you can use /mnt/c/projectpath, but if you try to docker run -v ${PWD}:/projectpath, you will find in the host that /projectpath/ is empty because on the host /mnt means nothing.

If you work from /c/projectpath though and THEN do docker run -v ${PWD}:/projectpath and you WILL find that in the container, /projectpath will reflect /c/projectpath in realtime. There are no errors or any other ways to detect this issue other than seeing empty mounts inside your guest.

You must also be sure to "share the drive" in the Docker for Windows settings.

Answer 4

you can use -v option from cli, this facility is not available via Dockerfile

docker run -t -i -v <host_dir>:<container_dir> ubuntu /bin/bash

where host_dir is the directory from host which you want to mount. you don't need to worry about directory of container if it doesn't exist docker will create it.

If you do any changes in host_dir from host machine (under root privilege) it will be visible to container and vice versa.

Answer 5

[UPDATE] As of ~June 2017, Docker for Mac takes care of all the annoying parts of this where you have to mess with VirtualBox. It lets you map basically everything on your local host using the /private prefix. More info here. [/UPDATE]

All the current answers talk about Boot2docker. Since that's now deprecated in favor of docker-machine, this works for docker-machine:

First, ssh into the docker-machine vm and create the folder we'll be mapping to:

docker-machine ssh $MACHINE_NAME "sudo mkdir -p \"$VOL_DIR\""

Now share the folder to VirtualBox:

WORKDIR=$(basename "$VOL_DIR")
vboxmanage sharedfolder add "$MACHINE_NAME" --name "$WORKDIR" --hostpath "$VOL_DIR" --transient

Finally, ssh into the docker-machine again and mount the folder we just shared:

docker-machine ssh $MACHINE_NAME "sudo mount -t vboxsf -o uid=\"$U\",gid=\"$G\" \"$WORKDIR\" \"$VOL_DIR\""

Note: for UID and GID you can basically use whatever integers as long as they're not already taken.

This is tested as of docker-machine 0.4.1 and docker 1.8.3 on OS X El Capitan.

Answer 6

For Windows 10 users, it is important to have the mount point inside the C:/Users/ directory. I tried for hours to get this to work. This post helped but it was not obvious at first as the solution for Windows 10 is a comment to an accepted answer. This is how I did it:

docker run -it -p 12001:80 -v //c/Users/C/Desktop/dockerStorage:/root/sketches \
<your-image-here> /bin/bash

Then to test it, you can do echo TEST > hostTest.txt inside your image. You should be able to see this new file in the local host folder at C:/Users/C/Desktop/dockerStorage/.