In a CI-setup I’m working on we’re using kubernetes to run a docker container which runs docker-compose which is performing end-to-end testing. As I was working on this setup, I noticed I couldn’t mount the filesystem through to the innermost container. I’ve set up a repo which reproduces the issue with just docker-compose here:
In the example above I’m basically running two layers of docker-compose and trying to set up a chain of volumes in order to pass the imagined source code through to the innermost container.
file system ---> system docker-compose ---> docker-compose image ---> container
The first volume seems to work as I can list the file before running the next instance of docker-compose. The second volume definition though seems to believe there are no files on the host (in the docker-compose container). I assume this has to do somehow with the fact that the docker-runtime is shared between the system and container docker-compose and that those files are the result of a volume.
I would be very happy if someone could help me understand what’s going on and what my options are at this point! 
Tested on
- Docker for Mac: 18.03.1-ce-mac65 (24312)
- Engine: 18.03.1-ce
- Compose: 1.21.1
How to try it yourself
git clone https://github.com/dnjstrom/bug-multi-docker-compose-volumes.git
cd bug-multi-docker-compose-volumes
docker-compose run --rm test
My output
The files in /outer and /inner should theoretically be the same, but they’re not.
❯ docker-compose run --rm test
Creating network compose_default with the default driver
Outer container:
/outer
total 16
drwxr-xr-x 6 root root 192 Jul 17 16:06 .
drwxr-xr-x 1 root root 4096 Jul 17 16:17 ..
-rw-r--r-- 1 root root 158 Jul 13 14:16 README.md
-rw-r--r-- 1 root root 292 Jul 17 16:13 docker-compose.test.yml
-rw-r--r-- 1 root root 168 Jul 17 16:17 docker-compose.yml
Inner container:
/inner
total 4
drwxr-xr-x 2 root root 40 Jul 17 16:13 .
drwxr-xr-x 1 root root 4096 Jul 17 16:17 ..