Mounting volume where host directory is different on CI server

General Discussions
1

Cross post - Mounting volume where host directory is different on CI server

Hi,

I’m encountering a problem and I’m not sure how to solve it. I have a docker compose file that mounts a volume from the host to the container. When running docker-compose up locally, the path on the host will always be the same. However, when running docker-compose up from the Continuous Integration (CI) server, the path is different.

For example, the docker-compose has the following

volumes:
  - ${HOME}/directory:/root/directory

I want to have the following when docker-compose is run on the CI server

volumes:
  - ${ANOTHER_VARIABLE}/mydir:/root/directory

I really don’t want to have two docker-compose.yml files. Does anyone have any ideas how to address this?

2

Why do you need to do this? What is in that directory? Bind mounts are usually eschewed when trying to be portable for this very reason.

3

The directory contains SSH keys. I actually found a solution.

I created a second docker-compose.ci_server.yml file, that contains the mount point. And in my CI server, I call

docker-compose -f docker-compose.yml -f docker-compose.ci_server.yml up

And it appears to replace the container /root/.ssh directory with the one I want from my CI server.

4

Glad you found a solution.

(Obligatory: Don’t run containers as root. Use USER)

5

Why not just use your own environment var and set it appropriately on both systems? That is sort of the point of env vars.

Alternatively, just use - “./mydir:/root/directory” and create a soft link to ./mydir from ${HOME}/mydir on one machine and from ${ANOTHER_VARIABLE}/directory on the other.

6

First, there may be multiple people running docker-compose locally.

Second, an environment variable requires system configuration. Since docker-compose doesn’t currently support advanced variable substitution, it’s not ideal since we would need to ensure that every local execution has this env var defined.

Third, a symbolic link requires every host to have it exist on the system. If the symlink isn’t on the system, the containers started from docker-compose won’t have the required volumes.

The solution I came up with has less chances of failing due to the host being “misconfigured”.