nixfiles/docs/deployment.md

Deployment and workflows

How boxes get deployed, the devshell commands that drive everyday work, secrets, dev VMs, and CI.

deploy-rs

Rendering

The top-level deploy-rs.nix renders the flake's deploy output:

• It collects nixos.systems and home-manager.homes (mangling @ in home names to -at-, since deploy-rs node names can't contain @). An assertion rejects name collisions between systems and homes.
• A system/home becomes a deploy node only when configuration.config.my.deploy.enable is true. The node config is the definitions of the box's my.deploy.node option, re-imported as a module so deploy-rs's submodule merging still applies.
• autoRollback and magicRollback are off globally; global sshOpts are [ "-i" ".keys/deploy.key" ] (set in flake.nix).
• The result is passed through lib.my.deploy-rs.filterOpts, which strips nulls so unset options don't override deploy-rs defaults, and exposed as deploy = deploy-rs.rendered.

Per-box nodes

The shared nixos/modules/deploy-rs.nix module provides my.deploy:

• my.deploy.enable defaults to true, but is automatically forced off for dev VMs and NixOS containers (my.build.isDevVM / boot.isContainer — containers are deployed through their host instead, see below). The installer also disables it explicitly.
• Node defaults: hostname = the box's FQDN, sshUser = "deploy", user = "root", sudo = "doas -u" (or sudo -u), sshOpts = the box's first OpenSSH port. The module creates the deploy system user (bash shell, wheel, keys from my.deploy.authorizedKeys, which defaults to .keys/deploy.pub).

Generated profiles deploy in this order:

1. system activates config.system.build.toplevel with switch-to-configuration switch, applies the /tmp cwd and systemd-boot loader.conf workarounds, then prunes old generations. keepGenerations controls how much history is retained; zero disables pruning.
2. container-<name> activates each my.containers.instances entry into /nix/var/nix/profiles/per-container/<name>/system. With hotReload (the default), it reloads systemd-nspawn@<name> and restarts only a stopped container or one still running the dummy init; otherwise it restarts the unit. The same generation cleanup applies.

Usage

• deploy .#<host> — the devshell's deploy is a wrapper that adds --skip-checks. Node names are the system names (deploy .#git).
• deploy-multi <hosts...> — loops deploy over several nodes (extra args via $O).
• deploy --boot .#<host> — stages the config as the boot default without live-switching (deploy-rs's --boot maps to the custom activation's boot phase, which also does the generation cleanup). Use it when a live switch would cut the box off mid-change (e.g. a router WAN rework), then reboot to cut over.
• nix flake check includes deploy-rs's own deployChecks for the whole deploy attrset.

ssh-machine

ssh-machine <name> [cmd] resolves user@host and the merged global/node sshOpts from .#deploy, using the same my.deploy.enable gate and @ → -at- mangling as deploy, then runs ssh. Boxes default to fish, so pipe multi-statement remote scripts through bash, for example ssh-machine <name> bash -s < script.sh. If a flaky agent stalls public-key authentication, use SSH_AUTH_SOCK= ssh-machine ….

Devshell commands

The repo ships a numtide/devshell (devshell/, entered via direnv). Run a command with no arguments for its help. From devshell/commands.nix:

Command	What it does
check-system <host> [nix args]	Evaluates .#nixosConfigurations."<host>".config.system.build.toplevel.drvPath — catches module/option errors without building. Prefer this to validate a config change.
build-system <host> [nix args]	Builds the system's toplevel (extra args pass through to nix build).
build-n-switch <args>	doas nixos-rebuild --flake . (adds the repo as a git safe.directory for root first).
build-home <name> [nix args]	Builds .#homeConfigurations."<name>".activationPackage.
home-switch [args]	home-manager switch --flake ..
deploy [args]	deploy-rs --skip-checks (wrapper package in devshell/default.nix).
deploy-multi <nodes...>	Deploys several nodes in sequence.
ssh-machine <name> [cmd]	SSH to a system or home by name, resolving target/options from its deploy-rs node (see above).
run-vm <host>	Boots a system as a dev VM: installs .keys/dev.key into a temp xchg/, then nix runs config.my.buildAs.devVM.
build-iso <host>	Builds config.my.buildAs.iso.
build-kexec <host>	Builds config.my.buildAs.kexecTree.
build-netboot <host>	Builds config.my.buildAs.netbootTree.
ragenix [args]	ragenix --identity .keys/dev.key (see Secrets).
repl	nix repl .#.
fmt [args]	nixpkgs-fmt (the canonical formatter).
update-nixpkgs	nix flake update nixpkgs-{unstable,stable,mine,mine-stable}.
update-home-manager	nix flake update home-manager-{unstable,stable}.
update-installer	Force-pushes the installer tag to trigger the installer release workflow.
home-link / home-unlink	Symlink (or remove) this flake.nix at ~/.config/home-manager/flake.nix for standalone home-manager use.
qemu-genmac	Prints a random QEMU-suitable MAC (52:54:00:xx:xx:xx).
ssh-get-ed25519 <host>	Prints a host's ed25519 pubkey via ssh-keyscan.
json2nix	Converts JSON on stdin to formatted Nix.

From devshell/install.nix (driven by $INSTALLER, the address of a running custom installer, SSHing as root with .keys/deploy.key):

Command	What it does
installer-shell [cmd]	Runs a command (default: a shell) inside the installer.
do-install [--no-bootloader] [--no-substitute] <system>	Builds the system's toplevel, nix copys it into the installer's target store, sets the system profile, and activates it with switch-to-configuration boot (with NIXOS_INSTALL_BOOTLOADER=1 unless --no-bootloader).

From devshell/vm-tasks.nix (remote VM consoles; they forward the VM's unix sockets from /run/vms/<vm>/ on <host> over SSH):

Command	What it does
vm-tty <host> <vm>	Serial TTY of a VM in minicom.
vm-monitor <host> <vm>	QEMU monitor socket in minicom.
vm-viewer <host> <vm>	SPICE display in virt-viewer (not on Darwin).

Nix implementation

Every context uses Determinate Nix as its nix.package, for its performance features (parallel evaluation and lazy trees) — not determinate-nixd; the daemon and nix.conf model are unchanged, and the Determinate NixOS module is deliberately not imported.

• Input and package. The determinate-nix input is the nix-src flake (flakehub.com/f/DeterminateSystems/nix-src), with nixpkgs.follows = "nixpkgs-unstable". We build it ourselves against our pinned nixpkgs — FlakeHub's own cache needs authentication, so there is nothing to gain from leaving it unpinned — and it then flows through the Harmonia cache like everything else. determinateOverlay exposes it under the stable attr determinate-nix, added to both the devshell pkgs' and the config configPkgs' overlay lists, so systems, homes and the devshell all resolve the same package (pkgs'.mine.determinate-nix).
• Settings. lib.my.c.nix.determinateSettings (lazy-trees, eval-cores = 0) is merged into nix.settings for systems and homes and into the devshell's nix.conf. These keys are only understood by the Determinate binary.
• Consumers follow automatically. Everything that shells out to Nix references config.nix.package (deploy-rs, containers, build, netboot, Harmonia), so they inherit Determinate without further change.
• accept-flake-config. Set true only in the devshell nix.conf, .envrc (as --accept-flake-config, for direnv) and CI — the contexts that build this flake — so its nixConfig (the Harmonia cache) is trusted without an interactive prompt. It is deliberately not set system-wide: boxes already trust that cache via nix.settings, so a global setting would only blanket-trust every flake's nixConfig for no gain.

Secrets

Secrets are age-encrypted files in secrets/, managed with ragenix (a fork with a rekey flag, from the flake inputs).

Per-box declarations

Each box declares my.secrets.key, the host public key its secrets encrypt to, and my.secrets.files.<name>, whose values merge settings such as owner and mode into the agenix secret. At runtime, identity paths come from the box's OpenSSH host keys. On tmproot boxes they are read from the persistence directory because agenix runs before the persisted keys would otherwise be available.

Recipient rules

secrets.nix is generated from every system's my.secrets.files and key. Each recipient list also includes .keys/dev.pub, so the development key can open every secret. Run ragenix -r after adding a box or secret to re-key the files.

Local keys and editing

The ragenix devshell command wraps ragenix --identity .keys/dev.key. The .keys/ directory contains that development key, the deploy key authorized for every box's deploy user, and other keys referenced by lib.my.c.sshKeyFiles; it is required for editing secrets, deploying and running development VMs.

Dev VMs

Any system can be built as a throwaway QEMU VM via config.my.buildAs.devVM (the build module extends the config with qemu-vm.nix and sets my.build.isDevVM). run-vm <host> creates a temp dir, installs .keys/dev.key as xchg/dev.key, and runs the VM; inside, the secrets module switches age.identityPaths to that dev key (my.secrets.vmKeyPath, default /tmp/xchg/dev.key), so dev VMs can decrypt the boxes' secrets without the real host keys. Dev VMs also get DHCP on eth0, an SSH port forward (host 2222 → guest 22), and are automatically excluded from deploy targets.

CI

GitHub/Gitea Actions workflows live in .gitea/workflows/.

ci.yaml

On pushes to master, this installs Determinate Nix on the runner (via DeterminateSystems/determinate-nix-action, configured with the same performance settings and Harmonia substituter as the boxes), runs nix flake check --no-build, then builds every attribute of .#ci.x86_64-linux: systems as system-<name>, homes as home-<name> (with @ changed to -at-), packages as package-<name>, and the development shell. Each result is pushed to the Harmonia cache with ci/push-to-cache.sh.

It then builds .#ciDrv.x86_64-linux, a linkFarm of all CI attributes, and pushes it with UPDATE_PROFILE=1. That updates the nixfiles profile on the cache box and collects old paths according to the workflow's retention setting. The SSH store uses /var/lib/harmonia, HARMONIA_SSH_KEY, and pinned ci/known_hosts; clients use https://nix-cache.nul.ie through lib.my.c.nix.cache.

installer.yaml

Pushing the installer tag (refreshed by update-installer) builds my.buildAs.iso and my.buildAs.netbootArchive, then attaches both to a release.

update-docs.yaml

On pushes to master, excluding its own commits, this runs the assignment, option and DNS reference generators and commits changed outputs as docs: Update generated references.

The docs generators

The generators are registered in pkgs/default.nix as wrappers around Python scripts under ci/. They leave the worktree unchanged when their output is current; the workflow stages docs/ and uses git diff --cached --quiet to decide whether to commit.

update-docs-assignments (ci/update-docs-assignments.py) evaluates .#nixfiles.config.nixos.allAssignments to JSON and rewrites the consolidated Box assignments tables in docs/networking.md — one table per site (colony / home / remote), each between a <!-- assignments: <site> --> marker and a closing <!-- assignments-end --> line. Boxes are grouped by site from their assignment domain, and each Box cell links to that box's page when one exists. Hand-written text in the Notes column is preserved across runs (keyed by box + assignment), so notes survive regeneration. Individual box pages don't carry tables; they link to the consolidated section.

update-docs-options (ci/update-docs-options.py) builds the nixos.optionsDoc output (declared in nixos/default.nix) — a nixosOptionsDoc JSON dump of the custom my.* options (declared with mkOpt' / mkBoolOpt' in nixos/modules/). It's evaluated against a minimal synthetic system, since the shared modules apply to every box, so defaults don't pick up a real host's values. The renderer writes docs/reference/nixos-options.md, one table per module file. The whole file is generated; edit the option descriptions in the modules, not the reference. The internal asX build-target options are marked internal = true so they're excluded.

update-docs-dns (ci/update-docs-dns.py) accepts forward and reverse zone names, discovers their authoritative nameservers through NS queries, and transfers each zone over AXFR. If a private reverse zone is not visible through the configured recursive resolver, it asks the authoritative servers discovered for the other requested zones. It updates only the matching <!-- dns: <zone> --> blocks in the DNS records reference; the page's headings and prose remain handwritten. Kea-managed owners are identified by DHCID records and removed together with their A, AAAA and PTR records; SOA records and TTLs are also omitted.