docs: Add a section on running your own Nixery

2 files changed, 145 insertions, 2 deletions

diff --git a/tools/nixery/docs/src/SUMMARY.md b/tools/nixery/docs/src/SUMMARY.md
index f5ba3e9b084a..677f328972bb 100644
--- a/tools/nixery/docs/src/SUMMARY.md
+++ b/tools/nixery/docs/src/SUMMARY.md
@@ -1,5 +1,7 @@
 # Summary
 
 - [Nixery](./nixery.md)
-- [Under the hood](./under-the-hood.md)
-- [Nix, the language](./nix-1p.md)
+  - [Under the hood](./under-the-hood.md)
+  - [Run your own Nixery](./run-your-own.md)
+- [Nix](./nix.md)
+  - [Nix, the language](./nix-1p.md)
diff --git a/tools/nixery/docs/src/run-your-own.md b/tools/nixery/docs/src/run-your-own.md
new file mode 100644
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@@ -0,0 +1,141 @@
+## Run your own Nixery
+
+<!-- markdown-toc start - Don't edit this section. Run M-x markdown-toc-refresh-toc -->
+
+- [0. Prerequisites](#0-prerequisites)
+- [1. Choose a package set](#1-choose-a-package-set)
+- [2. Build Nixery itself](#2-build-nixery-itself)
+- [3. Prepare configuration](#3-prepare-configuration)
+- [4. Deploy Nixery](#4-deploy-nixery)
+- [5. Productionise](#5-productionise)
+
+<!-- markdown-toc end -->
+
+
+---------
+
+⚠ This page is still under construction! ⚠
+
+--------
+
+Running your own Nixery is not difficult, but requires some setup. Follow the
+steps below to get up & running.
+
+*Note:* Nixery can be run inside of a [GKE][] cluster, providing a local service
+from which images can be requested. Documentation for how to set this up is
+forthcoming, please see [nixery#4][].
+
+## 0. Prerequisites
+
+To run Nixery, you must have:
+
+* [Nix][] (to build Nixery itself)
+* Somewhere to run it (your own server, Google AppEngine, a Kubernetes cluster,
+  whatever!)
+* A [Google Cloud Storage][gcs] bucket in which to store & serve layers
+
+## 1. Choose a package set
+
+When running your own Nixery you need to decide which package set you want to
+serve. By default, Nixery builds packages from a recent NixOS channel which
+ensures that most packages are cached upstream and no expensive builds need to
+be performed for trivial things.
+
+However if you are running a private Nixery, chances are high that you intend to
+use it with your own packages. There are three options available:
+
+1. Specify an upstream Nix/NixOS channel[^1], such as `nixos-19.03` or
+   `nixos-unstable`.
+2. Specify your own git-repository with a custom package set[^2]. This makes it
+   possible to pull different tags, branches or commits by modifying the image
+   tag.
+3. Specify a local file path containing a Nix package set. Where this comes from
+   or what it contains is up to you.
+
+## 2. Build Nixery itself
+
+Building Nixery creates a container image. This section assumes that the
+container runtime used is Docker, please modify instructions correspondingly if
+you are using something else.
+
+With a working Nix installation, building Nixery is done by invoking `nix-build
+-A nixery-image` from a checkout of the [Nixery repository][repo].
+
+This will create a `result`-symlink which points to a tarball containing the
+image. In Docker, this tarball can be loaded by using `docker load -i result`.
+
+## 3. Prepare configuration
+
+Nixery is configured via environment variables.
+
+You must set *all* of these:
+
+* `BUCKET`: [Google Cloud Storage][gcs] bucket to store & serve image layers
+* `PORT`: HTTP port on which Nixery should listen
+
+You may set *one* of these, if unset Nixery defaults to `nixos-19.03`:
+
+* `NIXERY_CHANNEL`: The name of a Nix/NixOS channel to use for building
+* `NIXERY_PKGS_REPO`: URL of a git repository containing a package set (uses
+  locally configured SSH/git credentials)
+* `NIXERY_PKGS_PATH`: A local filesystem path containing a Nix package set to use
+  for building
+
+You may set *both* of these:
+
+* `GCS_SIGNING_KEY`: A Google service account key (in PEM format) that can be
+  used to [sign Cloud Storage URLs][signed-urls]
+* `GCS_SIGNING_ACCOUNT`: Google service account ID that the signing key belongs
+  to
+
+To authenticate to the configured GCS bucket, Nixery uses Google's [Application
+Default Credentials][ADC]. Depending on your environment this may require
+additional configuration.
+
+## 4. Deploy Nixery
+
+With the above environment variables configured, you can run the image that was
+built in step 2.
+
+How this works depends on the environment you are using and is, for now, outside
+of the scope of this tutorial.
+
+Once Nixery is running you can immediately start requesting images from it.
+
+## 5. Productionise
+
+(⚠ Here be dragons! ⚠)
+
+Nixery is still an early project and has not yet been deployed in any production
+environments and some caveats apply.
+
+Notably, Nixery currently does not support any authentication methods, so anyone
+with network access to the registry can retrieve images.
+
+Running a Nixery inside of a fenced-off environment (such as internal to a
+Kubernetes cluster) should be fine, but you should consider to do all of the
+following:
+
+* Issue a TLS certificate for the hostname you are assigning to Nixery. In fact,
+  Docker will refuse to pull images from registries that do not use TLS (with
+  the exception of `.local` domains).
+* Configure signed GCS URLs to avoid having to make your bucket world-readable.
+* Configure request timeouts for Nixery if you have your own web server in front
+  of it. This will be natively supported by Nixery in the future.
+
+-------
+
+[^1]: Nixery will not work with Nix channels older than `nixos-19.03`.
+
+[^2]: This documentation will be updated with instructions on how to best set up
+    a custom Nix repository. Nixery expects custom package sets to be a superset
+    of `nixpkgs`, as it uses `lib` and other features from `nixpkgs`
+    extensively.
+
+[GKE]: https://cloud.google.com/kubernetes-engine/
+[nixery#4]: https://github.com/google/nixery/issues/4
+[Nix]: https://nixos.org/nix
+[gcs]: https://cloud.google.com/storage/
+[repo]: https://github.com/google/nixery
+[signed-urls]: under-the-hood.html#5-image-layers-are-requested
+[ADC]: https://cloud.google.com/docs/authentication/production#finding_credentials_automatically