oci-image: init scripts to build and upload image

Add image configuration for Oracle Cloud Infrastructure and scripts to
build and upload the image as a Custom Image.

nixos/maintainers/scripts/oci/create-image.sh

@@ -0,0 +1,10 @@
+#! /usr/bin/env bash
+
+export NIX_PATH=nixpkgs=$(dirname $(readlink -f $0))/../../../..
+export NIXOS_CONFIG=$(dirname $(readlink -f $0))/../../../modules/virtualisation/oci-image.nix
+
+nix-build '<nixpkgs/nixos>' \
+   -A config.system.build.OCIImage \
+   --argstr system x86_64-linux \
+   --option system-features kvm \
+   -o oci-image

nixos/maintainers/scripts/oci/upload-image.sh

@@ -0,0 +1,98 @@
+#! /usr/bin/env bash
+
+script_dir="$(dirname $(readlink -f $0))"
+nixpkgs_root="$script_dir/../../../.."
+export NIX_PATH="nixpkgs=$nixpkgs_root"
+
+cat - <<EOF
+This script will locally build a NixOS image and upload it as a Custom Image
+using oci-cli. Make sure that an API key for the tenancy administrator has been
+added to '~/.oci'.
+For more info about configuring oci-cli, please visit
+https://docs.cloud.oracle.com/iaas/Content/API/Concepts/apisigningkey.htm#Required_Keys_and_OCIDs
+
+EOF
+
+qcow="oci-image/nixos.qcow2"
+if [ ! -f "$qcow" ]; then
+    echo "OCI image $qcow does not exist"
+    echo "Building image with create-image.sh"
+    "$script_dir/create-image.sh"
+    [ -f "$qcow" ] || { echo "Build failed: image not present after build"; exit 1; }
+else
+    echo "Using prebuilt image $qcow"
+fi
+
+cli="$(
+  nix-build '<nixpkgs>' \
+    --no-out-link \
+    -A oci-cli
+)"
+
+PATH="$cli/bin:$PATH"
+bucket="_TEMP_NIXOS_IMAGES_$RANDOM"
+
+echo "Creating a temporary bucket"
+root_ocid="$(
+  oci iam compartment list \
+  --all \
+  --compartment-id-in-subtree true \
+  --access-level ACCESSIBLE \
+  --include-root \
+  --raw-output \
+  --query "data[?contains(\"id\",'tenancy')].id | [0]"
+)"
+bucket_ocid=$(
+  oci os bucket create \
+    -c "$root_ocid" \
+    --name "$bucket" \
+    --raw-output \
+    --query "data.id"
+)
+# Clean up bucket on script termination
+trap 'echo Removing temporary bucket; oci os bucket delete --force --name "$bucket"' INT TERM EXIT
+
+echo "Uploading image to temporary bucket"
+oci os object put -bn "$bucket" --file "$qcow"
+
+echo "Importing image as a Custom Image"
+bucket_ns="$(oci os ns get --query "data" --raw-output)"
+image_id="$(
+  oci compute image import from-object \
+    -c "$root_ocid" \
+    --namespace "$bucket_ns" \
+    --bucket-name "$bucket" \
+    --name nixos.qcow2 \
+    --operating-system NixOS \
+    --source-image-type QCOW2 \
+    --launch-mode PARAVIRTUALIZED \
+    --display-name NixOS \
+    --raw-output \
+    --query "data.id"
+)"
+
+cat - <<EOF
+Image created! Please mark all available shapes as compatible with this image by
+visiting the following link and by selecting the 'Edit Details' button on:
+https://cloud.oracle.com/compute/images/$image_id
+EOF
+
+# Workaround until https://github.com/oracle/oci-cli/issues/399 is addressed
+echo "Sleeping for 15 minutes before cleaning up files in the temporary bucket"
+sleep $((15 * 60))
+
+echo "Deleting image from bucket"
+par_id="$(
+  oci os preauth-request list \
+    --bucket-name "$bucket" \
+    --raw-output \
+    --query "data[0].id"
+)"
+
+if [[ -n $par_id ]]; then
+  oci os preauth-request delete \
+    --bucket-name "$bucket" \
+    --par-id "$par_id"
+fi
+
+oci os object delete -bn "$bucket" --object-name nixos.qcow2 --force

nixos/modules/virtualisation/oci-common.nix

@@ -0,0 +1,39 @@
+{ lib, pkgs, ... }:
+
+with lib;
+{
+  imports = [ ../profiles/qemu-guest.nix ];
+
+  # Taken from /proc/cmdline of Ubuntu 20.04.2 LTS on OCI
+  boot.kernelParams = [
+    "console=tty1"
+    "console=ttyS0"
+    "nvme.shutdown_timeout=10"
+    "libiscsi.debug_libiscsi_eh=1"
+    "crash_kexec_post_notifiers"
+  ];
+
+  boot.growPartition = true;
+
+  fileSystems."/" = {
+    device = "/dev/disk/by-label/nixos";
+    fsType = "ext4";
+    autoResize = true;
+  };
+
+  boot.loader.grub = {
+    version = 2;
+    device = "/dev/sda";
+    splashImage = null;
+    extraConfig = ''
+      serial --unit=0 --speed=115200 --word=8 --parity=no --stop=1
+      terminal_input --append serial
+      terminal_output --append serial
+    '';
+  };
+
+  # https://docs.oracle.com/en-us/iaas/Content/Compute/Tasks/configuringntpservice.htm#Configuring_the_Oracle_Cloud_Infrastructure_NTP_Service_for_an_Instance
+  networking.timeServers = [ "169.254.169.254" ];
+
+  services.openssh.enable = true;
+}

nixos/modules/virtualisation/oci-config-user.nix

@@ -0,0 +1,12 @@
+{ modulesPath, ... }:
+
+{
+  # To build the configuration or use nix-env, you need to run
+  # either nixos-rebuild --upgrade or nix-channel --update
+  # to fetch the nixos channel.
+
+  # This configures everything but bootstrap services,
+  # which only need to be run once and have already finished
+  # if you are able to see this comment.
+  imports = [ "${modulesPath}/virtualisation/oci-common.nix" ];
+}

nixos/modules/virtualisation/oci-image.nix

@@ -0,0 +1,49 @@
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  imports = [ ./oci-common.nix ];
+
+  config = {
+    system.build.OCIImage = import ../../lib/make-disk-image.nix {
+      inherit config lib pkgs;
+      name = "oci-image";
+      configFile = ./oci-config-user.nix;
+      format = "qcow2";
+      diskSize = 8192;
+    };
+
+    systemd.services.fetch-ssh-keys = {
+      description = "Fetch authorized_keys for root user";
+
+      wantedBy = [ "sshd.service" ];
+      before = [ "sshd.service" ];
+
+      after = [ "network-online.target" ];
+      wants = [ "network-online.target" ];
+
+      path  = [ pkgs.coreutils pkgs.curl ];
+      script = ''
+        mkdir -m 0700 -p /root/.ssh
+        if [ -f /root/.ssh/authorized_keys ]; then
+          echo "Authorized keys have already been downloaded"
+        else
+          echo "Downloading authorized keys from Instance Metadata Service v2"
+          curl -s -S -L \
+            -H "Authorization: Bearer Oracle" \
+            -o /root/.ssh/authorized_keys \
+            http://169.254.169.254/opc/v2/instance/metadata/ssh_authorized_keys
+          chmod 600 /root/.ssh/authorized_keys
+        fi
+      '';
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        StandardError = "journal+console";
+        StandardOutput = "journal+console";
+      };
+    };
+  };
+}