Basically, you can’t run a docker engine in a docker container, but in some use cases, you might still want to call docker client to build image and run container. In my use case is that I use docker executor in GitLab runner, and my apps are all deployed in docker containers, so I have to call call docker within the container at the deploy sequence.
The good thing is, docker client and docker engine can be seprated, and you can mirror the /var/run/docker.sock in container with the one your host machine which a docker engine runs within through docker volume.
In order to do the volume mirror, I edited the gitlab-runer config after it is configured as below.
1 | concurrent = 1 |
2 | check_interval = 0 |
3 | |
4 | [[runners]] |
5 | name = "my-runner" |
6 | url = "MY_GITLAB_URL" |
7 | token = "MY_TOKEN" |
8 | executor = "docker" |
9 | [runners.docker] |
10 | tls_verify = false |
11 | image = "docker:latest" |
12 | privileged = true |
13 | disable_cache = false |
14 | # mirror /var/run/docker.sock in your host that runs docker engine to your executor container |
15 | volumes = ["/var/run/docker.sock:/var/run/docker.sock", "/cache"] |
16 | cache_dir = "cache" |
17 | shm_size = 0 |
18 | [runners.cache] |
- I used the official docker image which contains a docker client, of course you can build customed image with docker client installed within, that is easy.
- I mirrored the host’s /var/run/docker.sock to gitlab-runner’s executor container so that the docker client in container can be used with a running docker engine. You’re welcome to do the config this volume in any other way you use docker like
docker runordocker-compose.
To build a customed image with docker client is simple, you just do the COPY like what I do in the Dockerfile given below.
1 | FROM YOUR_IMAGE |
2 | |
3 | # please download the docker client before you build the image at https://download.docker.com/linux/static/stable/x86_64/ . |
4 | COPY docker-ce.tgz /root/ |
5 | RUN cd /root/ \ |
6 | && tar xzvf docker-ce.tgz \ |
7 | && cp docker/* /usr/bin/ \ |
8 | && docker --version \ |
9 | && rm -rf /root/docker /root/docker-ce.tgz |
10 | |
11 | # please download the docker-compose from https://github.com/docker/compose/releases if you also want to use it. |
12 | COPY docker-compose /usr/local/bin/ |
13 | RUN chmod +x /usr/local/bin/docker-compose |