forked from Fachschaft/nixConfig
some documentation I wrote without proofreading at 2 in the morning
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dennis
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README.md
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README.md
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# nixConfig
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## Build a machine
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There are multiple ways to build and deploy a machine configuration. Which is the
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most appropriate depends on the context and scenario. So first there will be a general
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explanation how this works and afterwards we will talk about some scenarios.
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If you run `nix flake show` you should get an output similiar to this
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```
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$ nix flake show
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git+file:///home/nerf/git/nixConfig?ref=refs%2fheads%2fnyarlathtop&rev=9d0eb749287d1e9e793811759dfa29469ab706dc
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├───apps
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│ └───x86_64-linux
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├───checks
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│ └───x86_64-linux
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├───devShells
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│ └───x86_64-linux
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├───formatter
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├───legacyPackages
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│ └───x86_64-linux omitted (use '--legacy' to show)
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├───nixosConfigurations
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│ └───nyarlathotep: NixOS configuration
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├───nixosModules
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├───overlays
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└───packages
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└───x86_64-linux
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```
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we can see there is an output callled `nixosConfigurations.nyarlathotep`. Which contains the config of the machine
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called nyarlathotep. `nixosConfigurations` is special in that sense, that `nixos-rebuild` will automatically look
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for this key and assume how it is structured. The interesting part for us is the derivation `config.system.build.toplevel`.
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Its closure contains the whole system and the resulting derivation a script that changes the current system to
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that derivation. (called `/bin/switch-to-configuration`).
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So what we want to archive is populate the nix store of the target machine with the closure of the derivation
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`.#nixosConfigurations.<name>.config.system.build.toplevel` and run the the resulting script on the target machine.
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### Local
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If you want to build the machineconfiguration for machine <name>
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run
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It has multiple benefits to build the system config on the local computer and push it to the target server.
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For example one doesn't stress the server with the load coming with evaluating the expression. Also the server
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doesn't need to fetch the build dependencies this way. One has a local check if at least the nix syntax was correct.
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And so on...
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#### Build
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If you have this repository local in your current directory you can just run:
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```
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nix build .#nixosConfiguration.<name>.config.system.build.toplevel
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$ nix build .#nixosConfigurations.<name>.config.system.build.toplevel
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```
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But you don't need to clone this repository for more on flake urls see the `nix flake --help` documentation.
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#### Copy
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After we build the derivation we need to get the closure onto the target system. Luckily nix has tools to do that
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via ssh. We could just run:
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```
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$ nix copy -s --to <however you setup your ssh stuff> .#nixosConfigurations.<name>.config.system.build.toplevel
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```
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we do not need the flake anymore, instead of specifying the derivation name we could also give the store path
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directly.
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The `-s` is important it makes the target machine substitute all derivations it can (by default from chache.nixos.org).
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So you only upload config files and self build things.
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To be able to copy things to a machine they need to be signed by someone trusted. Additional trusted nix keys are handled
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in `./nixos/roles/nix_keys.nix`. So to get yourself trusted you either need to install one derivation from the machine itself,
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or find someone who is already trusted.
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For more information on signing and key creation see `nix store sign --help` and `nix key --help`.
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#### Activate
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Log into the remote machine and execute
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```
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# /nix/store/<storepath>/bin/switch-to-configuration boot
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```
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That will setup a configuration switch at reboot. You can also switch the configuration live. For more
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details consider the `--help` output of that script.
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If you have a `nixos-rebuild` available on your system it can automatize these things with the `--flake` and
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`--target-host` parameters. But there are some pitfalls so look at the `nixos-rebuild` documentation beforehand.
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### On the machine
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clone this repo to `/etc/nixos/` and `nixos-rebuild` that will select
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the appropriate machine based on hostname
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clone this repo to `/etc/nixos/` and `nixos-rebuild boot` or `nixos-rebuild switch` that will select
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the appropriate machine based on hostname.
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If the hostname is not correct, or you don't want to clone this flake you can also use the `--flake` parameter.
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In any case, to switch the system configuration you will need to have root priviledges on the target machine.
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### sops
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## How this flake is organized
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This flake uses `flake-parts` see [flake.parts](https://flake.parts) for more details. It makes handling
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`system` and some other moudles related things more convenient.
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For the general layout of nixos system config and modules, please see the corresponding documentation.
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The toplevel `flake.nix` contains the flake inputs as usual and only calls a file `flake-module.nix`
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this toplevel `flake-module.nix` imports further more specialiesed `flake-modules.nix` files from subdirectories.
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Right now the only one is `nixos/flake-module.nix`.
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the `nixos` folder contains all machine configurations. It sepreates in two folders `nixos/machines` and `nixos/roles`.
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`nixos/machines` contains all machine specific configuration (in a subfolder per machine). Like hardware configuration, specific
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network configuration. And service configuration that are too closely intervowen with the rest of that machine. It also
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contains the root config for that machine called `configuration.nix`. This file usually only includes other modules.
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`nixos/roles` contains config that is pontentially shared by some machines. It is expected that `nixos/roles/default.nix`
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is imported as (`../../roles`) in every machine. Notable are the files `nixos/roles/admins.nix` which contains
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common admin accounts for these machines and `nixos/roles/nix_keys.nix` which contains the additional trusted
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keys for the nix store.
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## sops
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We are sharing secrets using [`sops`](https://github.com/getsops/sops) and [`sops-nix`](https://github.com/Mic92/sops-nix)
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As of right now we use only `age` keys.
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@ -35,4 +132,3 @@ afterwards the secret should be available in `/run/secrets/example-key`.
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If the accessing process is not root it must be member of the group `config.users.groups.keys`
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for systemd services this can be archived by setting `serviceConfig.SupplementaryGroups = [ config.users.groups.keys.name ];`
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it the service config.
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