diff options
Diffstat (limited to 'nixos/modules/virtualisation/amazon-init.nix')
-rw-r--r-- | nixos/modules/virtualisation/amazon-init.nix | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/nixos/modules/virtualisation/amazon-init.nix b/nixos/modules/virtualisation/amazon-init.nix new file mode 100644 index 00000000000..4f2f8df90eb --- /dev/null +++ b/nixos/modules/virtualisation/amazon-init.nix @@ -0,0 +1,87 @@ +{ config, lib, pkgs, ... }: + +with lib; + +let + cfg = config.virtualisation.amazon-init; + + script = '' + #!${pkgs.runtimeShell} -eu + + echo "attempting to fetch configuration from EC2 user data..." + + export HOME=/root + export PATH=${pkgs.lib.makeBinPath [ config.nix.package pkgs.systemd pkgs.gnugrep pkgs.git pkgs.gnutar pkgs.gzip pkgs.gnused pkgs.xz config.system.build.nixos-rebuild]}:$PATH + export NIX_PATH=nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixos:nixos-config=/etc/nixos/configuration.nix:/nix/var/nix/profiles/per-user/root/channels + + userData=/etc/ec2-metadata/user-data + + # Check if user-data looks like a shell script and execute it with the + # runtime shell if it does. Otherwise treat it as a nixos configuration + # expression + if IFS= LC_ALL=C read -rN2 shebang < $userData && [ "$shebang" = '#!' ]; then + # NB: we cannot chmod the $userData file, this is why we execute it via + # `pkgs.runtimeShell`. This means we have only limited support for shell + # scripts compatible with the `pkgs.runtimeShell`. + exec ${pkgs.runtimeShell} $userData + fi + + if [ -s "$userData" ]; then + # If the user-data looks like it could be a nix expression, + # copy it over. Also, look for a magic three-hash comment and set + # that as the channel. + if sed '/^\(#\|SSH_HOST_.*\)/d' < "$userData" | grep -q '\S'; then + channels="$(grep '^###' "$userData" | sed 's|###\s*||')" + while IFS= read -r channel; do + echo "writing channel: $channel" + done < <(printf "%s\n" "$channels") + + if [[ -n "$channels" ]]; then + printf "%s" "$channels" > /root/.nix-channels + nix-channel --update + fi + + echo "setting configuration from EC2 user data" + cp "$userData" /etc/nixos/configuration.nix + else + echo "user data does not appear to be a Nix expression; ignoring" + exit + fi + else + echo "no user data is available" + exit + fi + + nixos-rebuild switch + ''; +in { + + options.virtualisation.amazon-init = { + enable = mkOption { + default = true; + type = types.bool; + description = '' + Enable or disable the amazon-init service. + ''; + }; + }; + + config = mkIf cfg.enable { + systemd.services.amazon-init = { + inherit script; + description = "Reconfigure the system from EC2 userdata on startup"; + + wantedBy = [ "multi-user.target" ]; + after = [ "multi-user.target" ]; + requires = [ "network-online.target" ]; + + restartIfChanged = false; + unitConfig.X-StopOnRemoval = false; + + serviceConfig = { + Type = "oneshot"; + RemainAfterExit = true; + }; + }; + }; +} |