nagios: various improvements

* structured config for main config file allows to launch nagios in
debug mode without having to write the whole config file by hand
* build time syntax check
* all options have types, one more example
* I find it misleading that the main nagios config file is linked in
/etc but that if you change the link in /etc/ and restart nagios, it
has no effect. Have nagios use /etc/nagios.cfg
* fix paths in example nagios config files, which allows to reuse it:
  services.nagios.objectDefs =
   (map (x: "${pkgs.nagios}/etc/objects/${x}.cfg")
   [ "templates" "timeperiods" "commands" ]) ++ [ ./main.cfg ]
* for the above reason, add mailutils to default plugins

Co-Authored-By: Aaron Andersen <aaron@fosslib.net>

nixos/modules/services/monitoring/nagios.nix

@@ -17,32 +17,39 @@ let
       preferLocalBuild = true;
     } "mkdir -p $out; ln -s $nagiosObjectDefs $out/";
 
-  nagiosCfgFile = pkgs.writeText "nagios.cfg"
+  nagiosCfgFile = let
-    ''
+    default = {
-      # Paths for state and logs.
+      log_file="${nagiosLogDir}/current";
-      log_file=${nagiosLogDir}/current
+      log_archive_path="${nagiosLogDir}/archive";
-      log_archive_path=${nagiosLogDir}/archive
+      status_file="${nagiosState}/status.dat";
-      status_file=${nagiosState}/status.dat
+      object_cache_file="${nagiosState}/objects.cache";
-      object_cache_file=${nagiosState}/objects.cache
+      temp_file="${nagiosState}/nagios.tmp";
-      temp_file=${nagiosState}/nagios.tmp
+      lock_file="/run/nagios.lock";
-      lock_file=/run/nagios.lock # Not used I think.
+      state_retention_file="${nagiosState}/retention.dat";
-      state_retention_file=${nagiosState}/retention.dat
+      query_socket="${nagiosState}/nagios.qh";
-      query_socket=${nagiosState}/nagios.qh
+      check_result_path="${nagiosState}";
-      check_result_path=${nagiosState}
+      command_file="${nagiosState}/nagios.cmd";
-      command_file=${nagiosState}/nagios.cmd
+      cfg_dir="${nagiosObjectDefsDir}";
-
+      nagios_user="nagios";
-      # Configuration files.
+      nagios_group="nagios";
-      #resource_file=resource.cfg
+      illegal_macro_output_chars="`~$&|'\"<>";
-      cfg_dir=${nagiosObjectDefsDir}
+      retain_state_information="1";
-
+    };
-      # Uid/gid that the daemon runs under.
+    lines = mapAttrsToList (key: value: "${key}=${value}") (default // cfg.extraConfig);
-      nagios_user=nagios
+    content = concatStringsSep "\n" lines;
-      nagios_group=nagios
+    file = pkgs.writeText "nagios.cfg" content;
-
+    validated =  pkgs.runCommand "nagios-checked.cfg" {preferLocalBuild=true;} ''
-      # Misc. options.
+      cp ${file} nagios.cfg
-      illegal_macro_output_chars=`~$&|'"<>
+      # nagios checks the existence of /var/lib/nagios, but
-      retain_state_information=1
+      # it does not exists in the build sandbox, so we fake it
-    ''; # "
+      mkdir lib
+      lib=$(readlink -f lib)
+      sed -i s@=${nagiosState}@=$lib@ nagios.cfg
+      ${pkgs.nagios}/bin/nagios -v nagios.cfg && cp ${file} $out
+    '';
+    defaultCfgFile = if cfg.validateConfig then validated else file;
+  in
+  if cfg.mainConfigFile == null then defaultCfgFile else cfg.mainConfigFile;
 
   # Plain configuration for the Nagios web-interface with no
   # authentication.
@@ -77,16 +84,11 @@ in
     (mkRemovedOptionModule [ "services" "nagios" "urlPath" ] "The urlPath option has been removed as it is hard coded to /nagios in the nagios package.")
   ];
 
+  meta.maintainers = with lib.maintainers; [ symphorien ];
+
   options = {
     services.nagios = {
-      enable = mkOption {
+      enable = mkEnableOption "<link xlink:href='http://www.nagios.org/'>Nagios</link> to monitor your system or network.";
-        default = false;
-        description = "
-          Whether to use <link
-          xlink:href='http://www.nagios.org/'>Nagios</link> to monitor
-          your system or network.
-        ";
-      };
 
       objectDefs = mkOption {
         description = "
@@ -94,12 +96,14 @@ in
           the hosts, host groups, services and contacts for the
           network that you want Nagios to monitor.
         ";
+        type = types.listOf types.path;
+        example = literalExample "[ ./objects.cfg ]";
       };
 
       plugins = mkOption {
         type = types.listOf types.package;
-        default = [pkgs.nagiosPluginsOfficial pkgs.ssmtp];
+        default = with pkgs; [ nagiosPluginsOfficial ssmtp mailutils ];
-        defaultText = "[pkgs.nagiosPluginsOfficial pkgs.ssmtp]";
+        defaultText = "[pkgs.nagiosPluginsOfficial pkgs.ssmtp pkgs.mailutils]";
         description = "
           Packages to be added to the Nagios <envar>PATH</envar>.
           Typically used to add plugins, but can be anything.
@@ -107,14 +111,29 @@ in
       };
 
       mainConfigFile = mkOption {
-        type = types.package;
+        type = types.nullOr types.package;
-        default = nagiosCfgFile;
+        default = null;
-        defaultText = "nagiosCfgFile";
         description = "
-          Derivation for the main configuration file of Nagios.
+          If non-null, overrides the main configuration file of Nagios.
         ";
       };
 
+      extraConfig = mkOption {
+        type = types.attrsOf types.str;
+        example = {
+          debug_level = "-1";
+          debug_file = "/var/log/nagios/debug.log";
+        };
+        default = {};
+        description = "Configuration to add to /etc/nagios.cfg";
+      };
+
+      validateConfig = mkOption {
+        type = types.bool;
+        default = pkgs.stdenv.hostPlatform == pkgs.stdenv.buildPlatform;
+        description = "if true, the syntax of the nagios configuration file is checked at build time";
+      };
+
       cgiConfigFile = mkOption {
         type = types.package;
         default = nagiosCGICfgFile;
@@ -126,6 +145,7 @@ in
       };
 
       enableWebInterface = mkOption {
+        type = types.bool;
         default = false;
         description = "
           Whether to enable the Nagios web interface.  You should also
@@ -165,7 +185,7 @@ in
     # This isn't needed, it's just so that the user can type "nagiostats
     # -c /etc/nagios.cfg".
     environment.etc = [
-      { source = cfg.mainConfigFile;
+      { source = nagiosCfgFile;
         target = "nagios.cfg";
       }
     ];
@@ -173,7 +193,7 @@ in
     environment.systemPackages = [ pkgs.nagios ];
     systemd.services.nagios = {
       description = "Nagios monitoring daemon";
-      path     = [ pkgs.nagios ];
+      path     = [ pkgs.nagios ] ++ cfg.plugins;
       wantedBy = [ "multi-user.target" ];
       after    = [ "network.target" ];
 
@@ -184,14 +204,9 @@ in
         RestartSec = 2;
         LogsDirectory = "nagios";
         StateDirectory = "nagios";
+        ExecStart = "${pkgs.nagios}/bin/nagios /etc/nagios.cfg";
+        X-ReloadIfChanged = nagiosCfgFile;
       };
-
-      script = ''
-        for i in ${toString cfg.plugins}; do
-          export PATH=$i/bin:$i/sbin:$i/libexec:$PATH
-        done
-        exec ${pkgs.nagios}/bin/nagios ${cfg.mainConfigFile}
-      '';
     };
 
     services.httpd.virtualHosts = optionalAttrs cfg.enableWebInterface {

pkgs/servers/monitoring/nagios/default.nix

@@ -20,6 +20,13 @@ stdenv.mkDerivation rec {
     substituteInPlace Makefile --replace '$(MAKE) install-basic' ""
   '';
   installTargets = "install install-config";
+  postInstall = ''
+    # don't make default files use hardcoded paths to commands
+    sed -i 's@command_line *[^ ]*/\([^/]*\) @command_line \1 @'  $out/etc/objects/commands.cfg
+    sed -i 's@/usr/bin/@@g' $out/etc/objects/commands.cfg
+    sed -i 's@/bin/@@g' $out/etc/objects/commands.cfg
+  '';
+
 
   meta = {
     description = "A host, service and network monitoring program";