6d8391a3ce
Similar to the `user` option, the added `group` option sets the group of the executing process. If not `null`, it also sets `DynamicUser=false`. In case `user` is set to `null` (the default), systemd would run the service as root implicitly. As this is dangerous and most certainly not what users want, we force them to set `user = "root"` explicitly if that's really their intention. That's achieved through an assertion.
300 lines
13 KiB
Nix
300 lines
13 KiB
Nix
{ config
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, lib
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, pkgs
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, ...
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}:
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with lib;
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{
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config.assertions = flatten (
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flip mapAttrsToList config.services.github-runners (name: cfg: map (mkIf cfg.enable) [
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{
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assertion = !cfg.noDefaultLabels || (cfg.extraLabels != [ ]);
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message = "`services.github-runners.${name}`: The `extraLabels` option is mandatory if `noDefaultLabels` is set";
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}
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{
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assertion = cfg.group == null || cfg.user != null;
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message = ''`services.github-runners.${name}`: Setting `group` while leaving `user` unset runs the service as `root`. If this is really what you want, set `user = "root"` explicitly'';
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}
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])
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);
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config.systemd.services = flip mapAttrs' config.services.github-runners (name: cfg:
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let
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svcName = "github-runner-${name}";
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systemdDir = "github-runner/${name}";
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# %t: Runtime directory root (usually /run); see systemd.unit(5)
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runtimeDir = "%t/${systemdDir}";
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# %S: State directory root (usually /var/lib); see systemd.unit(5)
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stateDir = "%S/${systemdDir}";
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# %L: Log directory root (usually /var/log); see systemd.unit(5)
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logsDir = "%L/${systemdDir}";
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# Name of file stored in service state directory
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currentConfigTokenFilename = ".current-token";
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workDir = if cfg.workDir == null then runtimeDir else cfg.workDir;
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# Support old github-runner versions which don't have the `nodeRuntimes` arg yet.
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package = cfg.package.override (old: optionalAttrs (hasAttr "nodeRuntimes" old) { inherit (cfg) nodeRuntimes; });
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in
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nameValuePair svcName {
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description = "GitHub Actions runner";
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wantedBy = [ "multi-user.target" ];
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wants = [ "network-online.target" ];
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after = [ "network.target" "network-online.target" ];
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environment = {
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HOME = workDir;
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RUNNER_ROOT = stateDir;
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} // cfg.extraEnvironment;
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path = (with pkgs; [
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bash
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coreutils
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git
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gnutar
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gzip
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]) ++ [
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config.nix.package
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] ++ cfg.extraPackages;
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serviceConfig = mkMerge [
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{
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ExecStart = "${package}/bin/Runner.Listener run --startuptype service";
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# Does the following, sequentially:
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# - If the module configuration or the token has changed, purge the state directory,
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# and create the current and the new token file with the contents of the configured
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# token. While both files have the same content, only the later is accessible by
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# the service user.
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# - Configure the runner using the new token file. When finished, delete it.
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# - Set up the directory structure by creating the necessary symlinks.
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ExecStartPre =
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let
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# Wrapper script which expects the full path of the state, working and logs
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# directory as arguments. Overrides the respective systemd variables to provide
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# unambiguous directory names. This becomes relevant, for example, if the
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# caller overrides any of the StateDirectory=, RuntimeDirectory= or LogDirectory=
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# to contain more than one directory. This causes systemd to set the respective
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# environment variables with the path of all of the given directories, separated
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# by a colon.
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writeScript = name: lines: pkgs.writeShellScript "${svcName}-${name}.sh" ''
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set -euo pipefail
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STATE_DIRECTORY="$1"
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WORK_DIRECTORY="$2"
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LOGS_DIRECTORY="$3"
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${lines}
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'';
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runnerRegistrationConfig = getAttrs [
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"ephemeral"
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"extraLabels"
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"name"
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"noDefaultLabels"
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"runnerGroup"
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"tokenFile"
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"url"
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"workDir"
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]
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cfg;
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newConfigPath = builtins.toFile "${svcName}-config.json" (builtins.toJSON runnerRegistrationConfig);
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currentConfigPath = "$STATE_DIRECTORY/.nixos-current-config.json";
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newConfigTokenPath = "$STATE_DIRECTORY/.new-token";
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currentConfigTokenPath = "$STATE_DIRECTORY/${currentConfigTokenFilename}";
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runnerCredFiles = [
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".credentials"
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".credentials_rsaparams"
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".runner"
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];
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unconfigureRunner = writeScript "unconfigure" ''
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copy_tokens() {
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# Copy the configured token file to the state dir and allow the service user to read the file
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install --mode=666 ${escapeShellArg cfg.tokenFile} "${newConfigTokenPath}"
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# Also copy current file to allow for a diff on the next start
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install --mode=600 ${escapeShellArg cfg.tokenFile} "${currentConfigTokenPath}"
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}
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clean_state() {
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find "$STATE_DIRECTORY/" -mindepth 1 -delete
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copy_tokens
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}
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diff_config() {
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changed=0
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# Check for module config changes
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[[ -f "${currentConfigPath}" ]] \
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&& ${pkgs.diffutils}/bin/diff -q '${newConfigPath}' "${currentConfigPath}" >/dev/null 2>&1 \
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|| changed=1
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# Also check the content of the token file
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[[ -f "${currentConfigTokenPath}" ]] \
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&& ${pkgs.diffutils}/bin/diff -q "${currentConfigTokenPath}" ${escapeShellArg cfg.tokenFile} >/dev/null 2>&1 \
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|| changed=1
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# If the config has changed, remove old state and copy tokens
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if [[ "$changed" -eq 1 ]]; then
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echo "Config has changed, removing old runner state."
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echo "The old runner will still appear in the GitHub Actions UI." \
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"You have to remove it manually."
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clean_state
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fi
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}
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if [[ "${optionalString cfg.ephemeral "1"}" ]]; then
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# In ephemeral mode, we always want to start with a clean state
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clean_state
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elif [[ "$(ls -A "$STATE_DIRECTORY")" ]]; then
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# There are state files from a previous run; diff them to decide if we need a new registration
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diff_config
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else
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# The state directory is entirely empty which indicates a first start
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copy_tokens
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fi
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# Always clean workDir
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find -H "$WORK_DIRECTORY" -mindepth 1 -delete
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'';
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configureRunner = writeScript "configure" ''
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if [[ -e "${newConfigTokenPath}" ]]; then
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echo "Configuring GitHub Actions Runner"
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args=(
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--unattended
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--disableupdate
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--work "$WORK_DIRECTORY"
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--url ${escapeShellArg cfg.url}
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--labels ${escapeShellArg (concatStringsSep "," cfg.extraLabels)}
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${optionalString (cfg.name != null ) "--name ${escapeShellArg cfg.name}"}
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${optionalString cfg.replace "--replace"}
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${optionalString (cfg.runnerGroup != null) "--runnergroup ${escapeShellArg cfg.runnerGroup}"}
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${optionalString cfg.ephemeral "--ephemeral"}
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${optionalString cfg.noDefaultLabels "--no-default-labels"}
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)
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# If the token file contains a PAT (i.e., it starts with "ghp_" or "github_pat_"), we have to use the --pat option,
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# if it is not a PAT, we assume it contains a registration token and use the --token option
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token=$(<"${newConfigTokenPath}")
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if [[ "$token" =~ ^ghp_* ]] || [[ "$token" =~ ^github_pat_* ]]; then
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args+=(--pat "$token")
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else
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args+=(--token "$token")
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fi
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${package}/bin/Runner.Listener configure "''${args[@]}"
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# Move the automatically created _diag dir to the logs dir
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mkdir -p "$STATE_DIRECTORY/_diag"
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cp -r "$STATE_DIRECTORY/_diag/." "$LOGS_DIRECTORY/"
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rm -rf "$STATE_DIRECTORY/_diag/"
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# Cleanup token from config
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rm "${newConfigTokenPath}"
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# Symlink to new config
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ln -s '${newConfigPath}' "${currentConfigPath}"
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fi
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'';
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setupWorkDir = writeScript "setup-work-dirs" ''
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# Link _diag dir
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ln -s "$LOGS_DIRECTORY" "$WORK_DIRECTORY/_diag"
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# Link the runner credentials to the work dir
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ln -s "$STATE_DIRECTORY"/{${lib.concatStringsSep "," runnerCredFiles}} "$WORK_DIRECTORY/"
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'';
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in
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map (x: "${x} ${escapeShellArgs [ stateDir workDir logsDir ]}") [
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"+${unconfigureRunner}" # runs as root
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configureRunner
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setupWorkDir
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];
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# If running in ephemeral mode, restart the service on-exit (i.e., successful de-registration of the runner)
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# to trigger a fresh registration.
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Restart = if cfg.ephemeral then "on-success" else "no";
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# If the runner exits with `ReturnCode.RetryableError = 2`, always restart the service:
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# https://github.com/actions/runner/blob/40ed7f8/src/Runner.Common/Constants.cs#L146
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RestartForceExitStatus = [ 2 ];
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# Contains _diag
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LogsDirectory = [ systemdDir ];
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# Default RUNNER_ROOT which contains ephemeral Runner data
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RuntimeDirectory = [ systemdDir ];
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# Home of persistent runner data, e.g., credentials
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StateDirectory = [ systemdDir ];
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StateDirectoryMode = "0700";
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WorkingDirectory = workDir;
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InaccessiblePaths = [
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# Token file path given in the configuration, if visible to the service
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"-${cfg.tokenFile}"
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# Token file in the state directory
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"${stateDir}/${currentConfigTokenFilename}"
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];
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KillSignal = "SIGINT";
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# Hardening (may overlap with DynamicUser=)
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# The following options are only for optimizing:
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# systemd-analyze security github-runner
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AmbientCapabilities = mkBefore [ "" ];
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CapabilityBoundingSet = mkBefore [ "" ];
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# ProtectClock= adds DeviceAllow=char-rtc r
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DeviceAllow = mkBefore [ "" ];
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NoNewPrivileges = mkDefault true;
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PrivateDevices = mkDefault true;
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PrivateMounts = mkDefault true;
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PrivateTmp = mkDefault true;
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PrivateUsers = mkDefault true;
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ProtectClock = mkDefault true;
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ProtectControlGroups = mkDefault true;
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ProtectHome = mkDefault true;
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ProtectHostname = mkDefault true;
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ProtectKernelLogs = mkDefault true;
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ProtectKernelModules = mkDefault true;
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ProtectKernelTunables = mkDefault true;
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ProtectSystem = mkDefault "strict";
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RemoveIPC = mkDefault true;
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RestrictNamespaces = mkDefault true;
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RestrictRealtime = mkDefault true;
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RestrictSUIDSGID = mkDefault true;
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UMask = mkDefault "0066";
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ProtectProc = mkDefault "invisible";
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SystemCallFilter = mkBefore [
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"~@clock"
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"~@cpu-emulation"
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"~@module"
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"~@mount"
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"~@obsolete"
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"~@raw-io"
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"~@reboot"
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"~capset"
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"~setdomainname"
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"~sethostname"
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];
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RestrictAddressFamilies = mkBefore [ "AF_INET" "AF_INET6" "AF_UNIX" "AF_NETLINK" ];
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BindPaths = lib.optionals (cfg.workDir != null) [ cfg.workDir ];
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# Needs network access
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PrivateNetwork = mkDefault false;
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# Cannot be true due to Node
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MemoryDenyWriteExecute = mkDefault false;
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# The more restrictive "pid" option makes `nix` commands in CI emit
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# "GC Warning: Couldn't read /proc/stat"
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# You may want to set this to "pid" if not using `nix` commands
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ProcSubset = mkDefault "all";
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# Coverage programs for compiled code such as `cargo-tarpaulin` disable
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# ASLR (address space layout randomization) which requires the
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# `personality` syscall
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# You may want to set this to `true` if not using coverage tooling on
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# compiled code
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LockPersonality = mkDefault false;
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DynamicUser = mkDefault true;
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}
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(mkIf (cfg.user != null) {
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DynamicUser = false;
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User = cfg.user;
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})
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(mkIf (cfg.group != null) {
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DynamicUser = false;
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Group = cfg.group;
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})
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cfg.serviceOverrides
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];
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}
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);
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}
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