add drone ci

drone-ci.md

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+# Drone CI
+
+When it comes to automation, [GitLab CI](https://gitlab.com) has been my go-to for running builds, tests and deployments of projects from static websites to 3D open-world games.
+This has generally been on a self-hosted installation, and often makes use of physical runners.
+However, I have some gripes: I mostly only use it for the CI, but it comes with an issue tracker and Git hosting solution too - great for some cases, but overkill in so many others.
+Because it's such a complete solution, GitLab is a bit of a resource hog, and can often run frustratingly slowly.
+
+Recently I've been playing with a friend's self-hosted instance of [Drone CI](https://drone.io/) as a lightweight alternative, and I much prefer it.
+I didn't set up the instance, so that part is out of scope for this post, but in case it's relevant, we're using a self-hosted [Gitea](gitea.io) instance to host the source.
+You can find out about configuring Drone with Gitea [here](https://docs.drone.io/server/provider/gitea/).
+
+
+## Yet Another Yaml Config
+
+Like GitLab, Drone is configured via a YAML file at the project root, called `.drone.yml`.
+Drone is configured by creating 'steps' to the pipeline, where GitLab uses 'jobs'.
+
+My first project's automation requirements were small - all I needed for a deployment was to copy all the files in a directory on every push to the `main` branch.
+This means I needed secure access to the host, and the ability to copy files to it.
+I didn't want to dedicate any permanent resources to such a small project, so opted for the `docker` pipeline option.
+
+My pipeline would contain a single `deploy` step which would configure SSH access to the host, and then use it to copy the relevant files from the checked out version of the project.
+I decided to use `ubuntu` as the Docker image for familiarity and accessibility - there are probably better options.
+Drone widely supports Docker image registries; I have not used Docker much, but would like to get more experience with it.
+
+```yml
+kind: pipeline
+type: docker
+name: deploy
+
+steps:
+- name: deploy
+  image: ubuntu
+  when:
+    branch:
+    - main
+
+  commands:
+    - echo hello world
+```
+
+## Secrets
+
+A hugely important aspect of automation is ensuring the security of one's pipelines.
+Automated access between pipelines is a big risk, and should be locked down as much as possible.
+For passing around secrets such as passwords and SSH keys, Drone has a concept of secrets.
+I created a private key on my local machine for the runner's access to the remote host, and added a [per-repository secret](https://docs.drone.io/secret/repository/) to contain the value.
+This is a named string value which can be accessed from within the context of a single pipeline step.
+
+I also created secrets to contain values for the remote host address and the user to login as.
+These are less of a security concern than the private SSH key, but we should obfuscate them anyway.
+It's also a useful step towards generalising the pipeline for other projects, which we'll get into later.
+
+This block was placed in the same step definition as above, below the `image:` entry:
+
+```
+environment:
+  HOST:
+    from_secret: host
+  USER:
+    from_secret: user
+  SSH_KEY:
+    from_secret: ssh_key
+```
+
+## Templates
+
+## References
+
+* [GitLab CI config to deploy via SSH](https://medium.com/@hfally/a-gitlab-ci-config-to-deploy-to-your-server-via-ssh-43bf3cf93775)
+