248 lines
9.2 KiB
Nix
248 lines
9.2 KiB
Nix
{ config
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, lib
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, pkgs
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, cfg ? config.services.github-runner
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, svcName
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, systemdDir ? "${svcName}/${cfg.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/${systemdDir}"
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# Name of file stored in service state directory
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, currentConfigTokenFilename ? ".current-token"
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, ...
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}:
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with lib;
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{
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description = "GitHub Actions runner";
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wantedBy = [ "multi-user.target" ];
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wants = [ "network-online.target" ];
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after = [ "network.target" "network-online.target" ];
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environment = {
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HOME = runtimeDir;
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RUNNER_ROOT = stateDir;
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} // cfg.extraEnvironment;
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path = (with pkgs; [
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bash
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coreutils
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git
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gnutar
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gzip
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]) ++ [
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config.nix.package
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] ++ cfg.extraPackages;
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serviceConfig = rec {
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ExecStart = "${cfg.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, runtime 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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RUNTIME_DIRECTORY="$2"
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LOGS_DIRECTORY="$3"
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${lines}
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'';
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currentConfigPath = "$STATE_DIRECTORY/.nixos-current-config.json";
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runnerRegistrationConfig = getAttrs [ "name" "tokenFile" "url" "runnerGroup" "extraLabels" "ephemeral" ] cfg;
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newConfigPath = builtins.toFile "${svcName}-config.json" (builtins.toJSON runnerRegistrationConfig);
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newConfigTokenFilename = ".new-token";
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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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differs=
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if [[ "$(ls -A "$STATE_DIRECTORY")" ]]; then
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# State directory is not empty
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# Set `differs = 1` if current and new runner config differ or if `currentConfigPath` does not exist
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${pkgs.diffutils}/bin/diff -q '${newConfigPath}' "${currentConfigPath}" >/dev/null 2>&1 || differs=1
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# Also trigger a registration if the token content changed
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${pkgs.diffutils}/bin/diff -q \
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"$STATE_DIRECTORY"/${currentConfigTokenFilename} \
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${escapeShellArg cfg.tokenFile} \
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>/dev/null 2>&1 || differs=1
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# If .credentials does not exist, assume a previous run de-registered the runner on stop (ephemeral mode)
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[[ ! -f "$STATE_DIRECTORY/.credentials" ]] && differs=1
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fi
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if [[ -n "$differs" ]]; then
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echo "Config has changed, removing old runner state."
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# In ephemeral mode, the runner deletes the `.credentials` file after de-registering it with GitHub
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[[ -f "$STATE_DIRECTORY/.credentials" ]] && 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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find "$STATE_DIRECTORY/" -mindepth 1 -delete
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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 ${escapeShellArg cfg.tokenFile} "$STATE_DIRECTORY/${newConfigTokenFilename}"
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# Also copy current file to allow for a diff on the next start
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install --mode=600 ${escapeShellArg cfg.tokenFile} "$STATE_DIRECTORY/${currentConfigTokenFilename}"
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fi
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'';
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configureRunner = writeScript "configure" ''
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if [[ -e "$STATE_DIRECTORY/${newConfigTokenFilename}" ]]; then
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echo "Configuring GitHub Actions Runner"
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args=(
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--unattended
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--disableupdate
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--work "$RUNTIME_DIRECTORY"
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--url ${escapeShellArg cfg.url}
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--labels ${escapeShellArg (concatStringsSep "," cfg.extraLabels)}
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--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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)
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# If the token file contains a PAT (i.e., it starts with "ghp_"), 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=$(<"$STATE_DIRECTORY/${newConfigTokenFilename}")
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if [[ "$token" =~ ^ghp_* ]]; 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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${cfg.package}/bin/config.sh "''${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 "$STATE_DIRECTORY/${newConfigTokenFilename}"
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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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setupRuntimeDir = writeScript "setup-runtime-dirs" ''
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# Link _diag dir
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ln -s "$LOGS_DIRECTORY" "$RUNTIME_DIRECTORY/_diag"
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# Link the runner credentials to the runtime dir
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ln -s "$STATE_DIRECTORY"/{${lib.concatStringsSep "," runnerCredFiles}} "$RUNTIME_DIRECTORY/"
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'';
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in
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map (x: "${x} ${escapeShellArgs [ stateDir runtimeDir logsDir ]}") [
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"+${unconfigureRunner}" # runs as root
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configureRunner
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setupRuntimeDir
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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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# 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 = runtimeDir;
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InaccessiblePaths = [
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# Token file path given in the configuration
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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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# By default, use a dynamically allocated user
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DynamicUser = true;
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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 = "";
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CapabilityBoundingSet = "";
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# ProtectClock= adds DeviceAllow=char-rtc r
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DeviceAllow = "";
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NoNewPrivileges = true;
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PrivateDevices = true;
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PrivateMounts = true;
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PrivateTmp = true;
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PrivateUsers = true;
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ProtectClock = true;
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ProtectControlGroups = true;
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ProtectHome = true;
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ProtectHostname = true;
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ProtectKernelLogs = true;
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ProtectKernelModules = true;
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ProtectKernelTunables = true;
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ProtectSystem = "strict";
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RemoveIPC = true;
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RestrictNamespaces = true;
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RestrictRealtime = true;
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RestrictSUIDSGID = true;
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UMask = "0066";
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ProtectProc = "invisible";
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SystemCallFilter = [
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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 = [ "AF_INET" "AF_INET6" "AF_UNIX" "AF_NETLINK" ];
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# Needs network access
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PrivateNetwork = false;
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# Cannot be true due to Node
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MemoryDenyWriteExecute = 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 = "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 = false;
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} // (
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if cfg.user == null then { DynamicUser = true; } else { User = cfg.user; }
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) // cfg.serviceOverrides;
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}
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