Docker container doesn't see files on windows volumes when the volume endpoint isn't on the drive C:

Question

I want to use a docker image in my work process. For example I want to use larryprice/sass to compile my SASS files to CSS. This image is pretty simple:

FROM ruby:2.2 
RUN gem install sass 
WORKDIR /tmp 
ENTRYPOINT ["sass", "--watch", "/src"]

I'm using Windows 10, Docker 1.11 and VirtualBox 5.0.16.

My project files placed on work SSD, that mapped to logical drive D - D:\\Projects\\Foo\\Bar\\web\\sass

So, my problem is following: when I attach a volume to the container from drive D: (by $PWD or by full path in MINGW style /D/Projects/Foo/Bar/web/sass) eg

cd /D/Projects/Foo/Bar/web
docker run --name sass -v $PWD/sass:/src --rm larryprice/sass

the container can't see any SASS files:

$ docker exec -i -t sass /bin/bash
root@541aabac9ceb:/tmp# ls -al /src/
total 4
drwxr-xr-x  2 root root   40 May  3 13:05 .
drwxr-xr-x 50 root root 4096 May  3 13:05 ..

But when I mount a volume from system disk (C:) all works fine:

$ docker run --name sass -v ~/sass:/src --rm larryprice/sass
[Listen warning]:
  Listen will be polling for changes. Learn more at https://github.com/guard/listen#polling-fallback.
>>> Sass is watching for changes. Press Ctrl-C to stop.
>>> New template detected: ../src/test.sass
      write /src/test.css
      write /src/test.css.map

How I can mount volumes from any place I need in Windows? Or what I'm doing wrong in my case?

ps Add leading slash to the path also not working:

docker run --name sass -v //d/Projects/Foo/Bar/web/sass:/src --rm larryprice/sass

Answer 1

Okay. Finally I found an explanation and solution for my own question. This solution will work for both Windows and MacOS X (because both of them uses VirtualBox to make Docker do the things).

The source of the problem consists from two points:

1. By default, VirtualBox VM have limited access to the host filesystem ( proof ). In my case it have access to the users folder on drive C: via VBox shared folder ( screen ). Thank to this, I can use volumes mapping like this one: ~/sass:/src (or full path: /c/users/dbykadorov/sass). Unfortunately, this configuration not allows me to use any path outside from /c/users/.

Solution for this point: add another shared folder to the VM, pointed on directory I need. I created new share d:/Projects ( screen ). Reboot your VM.

I hope here you'll complete your case. But in my case, VirtualBox does not mount new shared folder at system startup. So, I got second problem:

2. VirualBox does not mount additional shared folder, that I just added.

Additional solution :

Let's try to mount shared folder manually. Log into VM by any available ways. In console:

# Create mount point directory
$ mkdir -p /d/Projects
# Mount shared folder
$ mount -t vboxsf d/Projects /d/Projects

Okay, this do the trick! Now I can mount any project's directory (within D:\\Projects)!

But... when I'll reboot my VM the mountpoint will disappear =( Now we need to make our mount point more persistent. As described here :

# Make a file bootlocal.sh
$ touch /var/lib/boot2docker/bootlocal.sh
# Edit it
$ vi /var/lib/boot2docker/bootlocal.sh
# Add follovin lines here:
#!/bin/sh
mkdir -p /d/Projects
mount -t vboxsf d/Projects /d/Projects
# Save the file and reboot VM

Important note : to make volumes creating more clear it will be good idea to mount shared folder to the same path as on the host. Eg if we need to create volumes from E:\\Foo\\Bar\\Baz (/e/Foo/Bar/Baz in MINGW style) then we need to add new shared folder for E:\\Foo\\Bar\\Baz and mount it exactly to /e/Foo/Bar/Baz in your Docker VM.

That is All.