feat(corp/ops): add NixOS profile for Yandex Cloud machines r/6111

Sets up a virtual machine image that is bootable on Yandex Cloud.

There are some slightly wonky behaviours still, like cloud-init
apparently putting all keys into root's authorized_keys no matter what
is specified in the metadata, but it does work now.

Change-Id: I57dcb7fcfa6872a28855dc1347f73a6db3c56828
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8496
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

3 files changed, 89 insertions, 0 deletions

diff --git a/corp/ops/default.nix b/corp/ops/default.nix
index 87f71da786..dfa62c80ba 100644
--- a/corp/ops/default.nix
+++ b/corp/ops/default.nix
@@ -34,4 +34,13 @@ depot.nix.readTree.drvTargets rec {
 
     yc.attr = "corp.ops.yc-cli";
   };
+
+  # Base image for Yandex VMs.
+  yandex-base-image = (depot.third_party.nixos {
+    configuration = { ... }: {
+      imports = [
+        (depot.path.origSrc + ("/corp/ops/modules/yandex-cloud.nix"))
+      ];
+    };
+  }).config.system.build.yandexCloudImage;
 }
diff --git a/corp/ops/modules/.skip-tree b/corp/ops/modules/.skip-tree
new file mode 100644
index 0000000000..a6f528167f
--- /dev/null
+++ b/corp/ops/modules/.skip-tree
@@ -0,0 +1 @@
+Only NixOS modules here.
diff --git a/corp/ops/modules/yandex-cloud.nix b/corp/ops/modules/yandex-cloud.nix
new file mode 100644
index 0000000000..cca81bc0ca
--- /dev/null
+++ b/corp/ops/modules/yandex-cloud.nix
@@ -0,0 +1,79 @@
+# Profile for virtual machines on Yandex Cloud, intended for disk
+# images.
+#
+# https://cloud.yandex.com/en/docs/compute/operations/image-create/custom-image
+#
+# TODO(tazjin): Upstream to nixpkgs once it works well.
+{ config, lib, pkgs, modulesPath, ... }:
+
+let
+  cfg = config.virtualisation.yandexCloud;
+
+  # Kernel modules required for interacting with the hypervisor. These
+  # must be available during stage 1 boot and during normal operation,
+  # as disks and network do not work without them.
+  modules = [
+    "virtio-net"
+    "virtio-blk"
+    "virtio-pci"
+    "virtiofs"
+  ];
+in
+{
+  imports = [
+    "${modulesPath}/profiles/headless.nix"
+  ];
+
+  options = {
+    virtualisation.yandexCloud.rootPartitionUuid = with lib; mkOption {
+      type = types.str;
+      default = "C55A5EE2-E5FA-485C-B3AE-CC928429AB6B";
+
+      description = ''
+        UUID to use for the root partition of the disk image. Yandex
+        Cloud requires that root partitions are mounted by UUID.
+
+        Most users do not need to set this to a non-default value.
+      '';
+    };
+  };
+
+  config = {
+    fileSystems."/" = {
+      device = "/dev/disk/by-uuid/${lib.toLower cfg.rootPartitionUuid}";
+      fsType = "ext4";
+      autoResize = true;
+    };
+
+    boot = {
+      loader.grub.device = "/dev/vda";
+
+      initrd.kernelModules = modules;
+      kernelModules = modules;
+      kernelParams = [
+        # Enable support for the serial console
+        "console=ttyS0"
+      ];
+
+      growPartition = true;
+    };
+
+    environment.etc.securetty = {
+      text = "ttyS0";
+      mode = "0644";
+    };
+
+    systemd.services."serial-getty@ttyS0".enable = true;
+
+    services.openssh.enable = true;
+    services.cloud-init.enable = true;
+
+    system.build.yandexCloudImage = import (pkgs.path + "/nixos/lib/make-disk-image.nix") {
+      inherit lib config pkgs;
+      additionalSpace = "128M";
+      format = "qcow2";
+      partitionTableType = "legacy+gpt";
+      rootGPUID = cfg.rootPartitionUuid;
+    };
+  };
+}