Add service for exporting journalctl logs

- Export logs every five minutes to /output/logs
- Attempt to export logs on shutdown, not fully functional yet
- Change audio-recorder service unitConfig after target to multi-user

Signed-off-by: Satu Koskinen <satu.a.koskinen@gmail.com>

flake.nix

@@ -42,6 +42,7 @@
         modules = [
           ./targets/raspberry-pi-4
           ./modules/audio-recorder
+          ./modules/logging
           ./modules/real-time-clock/i2c-rtc.nix
           ./modules/shutdown-button/service.nix
           nixos-hardware.nixosModules.raspberry-pi-4

modules/audio-recorder/default.nix

@@ -73,7 +73,7 @@
         Restart = "always";
       };
       unitConfig = {
-        After = "sound.target";
+        After = ["multi-user.target"];
       };
       startLimitIntervalSec = 0;
     };

modules/logging/default.nix

@@ -0,0 +1,61 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}: {
+  options = with lib; {
+    services.journalctl-log-export = {
+      enable = mkEnableOption "Enable exporting journalctl logs to a file.";
+
+      output-folder = mkOption {
+        type = types.str;
+        default = "/output/logs";
+        description = "The folder to save logs to.";
+      };
+    };
+  };
+
+  config = lib.mkIf config.services.journalctl-log-export.enable {
+    systemd.services.journalctl-log-export-on-shutdown = {
+      description = "Journalctl log export on shutdown service";
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        User = "root";
+        Type = "oneshot";
+        RemainAfterExit = true;
+        ExecStart = "${pkgs.coreutils}/bin/mkdir -p ${config.services.journalctl-log-export.output-folder}";
+        ExecStop = ''${pkgs.bash}/bin/bash -c "echo 'Exporting logs at shutdown' && journalctl --boot 0 > ${config.services.journalctl-log-export.output-folder}/$(date +\"%Y_%m_%d-%H_%M_%S\")_journalctl_on_shutdown.txt"'';
+      };
+    };
+
+    systemd.services.journalctl-log-export = {
+      description = "Journalctl log export service";
+      script = ''
+        #!/usr/bin/env bash
+        set -x
+        ${pkgs.coreutils}/bin/echo "Exporting journalctl logs"
+        ${pkgs.coreutils}/bin/mkdir -p ${config.services.journalctl-log-export.output-folder}
+        # if environment variable for output file name is not set, set it with systemctl set-environment
+        if [ -z "$JOURNALCTL_LOG_EXPORT_OUTPUT_FILE" ]; then
+          JOURNALCTL_LOG_EXPORT_OUTPUT_FILE=$(${pkgs.coreutils}/bin/date +"%Y_%m_%d-%H_%M_%S")_journalctl.txt
+          ${pkgs.systemd}/bin/systemctl set-environment JOURNALCTL_LOG_EXPORT_OUTPUT_FILE=$JOURNALCTL_LOG_EXPORT_OUTPUT_FILE
+        fi
+        ${pkgs.systemd}/bin/journalctl --boot 0 > ${config.services.journalctl-log-export.output-folder}/$JOURNALCTL_LOG_EXPORT_OUTPUT_FILE
+      '';
+      serviceConfig = {
+        User = "root";
+        Type = "oneshot";
+      };
+    };
+
+    systemd.timers.journalctl-log-export = {
+    wantedBy = [ "timers.target" ];
+    partOf = [ "journalctl-log-export.service" ];
+    timerConfig = {
+        OnCalendar = "*:0/5"; # every five minutes
+        Unit = "journalctl-log-export.service";
+    };
+};
+  };
+}

targets/raspberry-pi-4/default.nix

@@ -45,6 +45,11 @@ in {
     max-file-time-secs = 60;
   };
 
+  services.journalctl-log-export = {
+    enable = true;
+    output-folder = "/output/logs";
+  };
+
   services.gps-recorder = {
     enable = true;
     output-path = "/output/gps";