Commit 45f4cc6e authored by Achilleas Pipinellis's avatar Achilleas Pipinellis

Merge branch 'fix/docker-in-docker-ci-documentation' into 'master'

Update using_docker_build.md, clarify the 'privileged' mode requirement

Related to #15428

Fixes gitlab-org/gitlab-ci-multi-runner#1261

See merge request !3909
parents 7aff855b 8b09dafb
......@@ -75,37 +75,80 @@ For more information please checkout [On Docker security: `docker` group conside
## 2. Use docker-in-docker executor
Second approach is to use special Docker image with all tools installed (`docker` and `docker-compose`) and run build script in context of that image in privileged mode.
The second approach is to use the special Docker image with all tools installed
(`docker` and `docker-compose`) and run the build script in context of that
image in privileged mode.
In order to do that follow the steps:
1. Install [GitLab Runner](https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/#installation).
1. Register GitLab Runner from command line to use `docker` and `privileged` mode:
1. Register GitLab Runner from the command line to use `docker` and `privileged`
mode:
```bash
$ sudo gitlab-runner register -n \
sudo gitlab-runner register -n \
--url https://gitlab.com/ci \
--token RUNNER_TOKEN \
--executor docker \
--description "My Docker Runner" \
--docker-image "gitlab/dind:latest" \
--docker-image "docker:latest" \
--docker-privileged
```
The above command will register new Runner to use special [gitlab/dind](https://registry.hub.docker.com/u/gitlab/dind/) image which is provided by GitLab Inc.
The image at the start runs Docker daemon in [docker-in-docker](https://blog.docker.com/2013/09/docker-can-now-run-within-docker/) mode.
The above command will register a new Runner to use the special
`docker:latest` image which is provided by Docker. **Notice that it's using
the `privileged` mode to start the build and service containers.** If you
want to use [docker-in-docker] mode, you always have to use `privileged = true`
in your Docker containers.
The above command will create a `config.toml` entry similar to this:
```
[[runners]]
url = "https://gitlab.com/ci"
token = TOKEN
executor = "docker"
[runners.docker]
tls_verify = false
image = "docker:latest"
privileged = true
disable_cache = false
volumes = ["/cache"]
[runners.cache]
Insecure = false
```
If you want to use the Shared Runners available on your GitLab CE/EE
installation in order to build Docker images, then make sure that your
Shared Runners configuration has the `privileged` mode set to `true`.
1. You can now use `docker` from build script:
```yaml
image: docker:latest
services:
- docker:dind
before_script:
- docker info
build_image:
build:
stage: build
script:
- docker build -t my-docker-image .
- docker run my-docker-image /script/to/run/tests
```
1. However, by enabling `--docker-privileged` you are effectively disables all security mechanisms of containers and exposing your host to privilege escalation which can lead to container breakout.
For more information, check out [Runtime privilege](https://docs.docker.com/reference/run/#runtime-privilege-linux-capabilities-and-lxc-configuration).
\ No newline at end of file
1. However, by enabling `--docker-privileged` you are effectively disabling all
the security mechanisms of containers and exposing your host to privilege
escalation which can lead to container breakout.
For more information, check out the official Docker documentation on
[Runtime privilege and Linux capabilities][docker-cap].
An example project using this approach can be found here: https://gitlab.com/gitlab-examples/docker.
[docker-in-docker]: https://blog.docker.com/2013/09/docker-can-now-run-within-docker/
[docker-cap]: https://docs.docker.com/reference/run/#runtime-privilege-and-linux-capabilities
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