Merge branch 'hydra-images' into 'main'

Hydra images

See merge request ahoneybun/ahoneybun-net!10

content/posts/hydra-ci-images.md

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++++
+title = "Using Hydra to build custom images"
+date = 2025-07-31
+draft = false
+
+[taxonomies]
+categories = [ "nixos" ]
+tags = [ "nixos", "nixos-server", "nixos-25.05", "hydra", "custom-images"]
++++
+
+# Building custom images
+
+You can build images with either the legacy (non-flake) and flake method, there are a few great resources such as [nix.dev](https://nix.dev/tutorials/nixos/building-bootable-iso-image) and [NixOS Wiki](https://nixos.wiki/wiki/Creating_a_NixOS_live_CD). For example if we wanted a minimal (CLI only) ISO for x86_64 with helix and git we can do that here: 
+
+```nix,linenos
+{
+  description = "Minimal NixOS installation media";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+  outputs = { self, nixpkgs }: {
+    nixosConfigurations = {
+      exampleIso = nixpkgs.lib.nixosSystem {
+        system = "x86_64-linux";
+        modules = [
+          ({ pkgs, modulesPath, ... }: {
+            imports = [ (modulesPath + "/installer/cd-dvd/installation-cd-minimal.nix") ];
+            environment.systemPackages with pkgs; = [ helix git ];
+          })
+        ];
+      };
+    };
+  };
+}
+```
+
+We would build the image like this using flakes:
+
+```nix,linenos
+git init
+git add flake.nix
+nix build .#nixosConfigurations.exampleIso.config.system.build.images.iso
+```
+
+I started my own [nixos live disk repository](https://gitlab.com/ahoneybun-nix/nixos-live-disk) recently for building images for my Pi 4, Pi 5 and x86_64 minimal CLI versions.
+
+If we want to build an image for aarch64-linux with the graphical installer for GNOME with the latest kernel, hostname set and helix.
+
+```nix,linenos
+{
+  description = "Minimal NixOS installation media";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
+  outputs = {self, nixpkgs }: {
+    nixosConfigurations = {
+      drack = nixpkgs.lib.nixosSystem {
+        system = "aarch64-linux";
+        modules = [
+          ({ pkgs, lib, modulesPath, ... }: {
+            imports = [ "${modulesPath}/installer/cd-dvd/installation-cd-graphical-calamares-gnome.nix" ];
+            boot.kernelPackages = pkgs.linuxPackages_latest;
+            boot.supportedFilesystems = lib.mkForce [ "btrfs" "reiserfs" "vfat" "f2fs" "xfs" "ntfs" "cifs" ];
+            environment.systemPackages = with pkgs; [ helix ];
+            networking.hostName = "drack";
+            services.openssh.enable = true;
+            system.stateVersion = "25.05";
+          })
+        ];
+      };
+    };
+  };
+}
+```
+
+# Having Hydra get a job
+
+With the following in the flake we can have Hydra start building the images:
+
+```nix,linenos
+    hydraJobs = {
+      images = {
+        vetra = self.nixosConfigurations.vetra.config.system.build.sdImage;
+        sidera = self.nixosConfigurations.sidera.config.system.build.sdImage;
+        drack = self.nixosConfigurations.drack.config.system.build.isoImage;
+        test-gui = self.nixosConfigurations.test-gui.config.system.build.isoImage;
+        test-cli = self.nixosConfigurations.test-cli.config.system.build.isoImage;
+      };
+    };
+```
+
+{{ figure(src="/images/hydra-ci-images/hydra-custom-images.png", alt="Hydra building images for different architectures", caption="Hydra building images for different architectures") }}
+
+# Other questions
+
+Reach out to me on Mastodon for questions!