Merge pull request #17822 from abbradar/systemd-mounts

nixos filesystems: unify special filesystems handling

nixos/modules/tasks/filesystems.nix

@@ -18,6 +18,8 @@ let
 
   prioOption = prio: optionalString (prio != null) " pri=${toString prio}";
 
+  specialFSTypes = [ "proc" "sysfs" "tmpfs" "devtmpfs" "devpts" ];
+
   fileSystemOpts = { name, config, ... }: {
 
     options = {
@@ -97,11 +99,22 @@ let
         description = "Disable running fsck on this filesystem.";
       };
 
+      early = mkOption {
+        default = false;
+        type = types.bool;
+        internal = true;
+        description = ''
+	  Mount this filesystem very early during boot. At the moment of
+	  mounting no disks are exposed, so this option is primarily for
+          special file systems.
+        '';
+      };
+
     };
 
     config = {
       mountPoint = mkDefault name;
-      device = mkIf (config.fsType == "tmpfs") (mkDefault config.fsType);
+      device = mkIf (elem config.fsType specialFSTypes) (mkDefault config.fsType);
       options = mkIf config.autoResize [ "x-nixos.autoresize" ];
 
       # -F needed to allow bare block device without partitions
@@ -110,6 +123,13 @@ let
 
   };
 
+  # Makes sequence of `specialMount device mountPoint options fsType` commands.
+  # `systemMount` should be defined in the sourcing script.
+  makeSpecialMounts = mounts:
+    pkgs.writeText "mounts.sh" (concatMapStringsSep "\n" (mount: ''
+      specialMount "${mount.device}" "${mount.mountPoint}" "${concatStringsSep "," mount.options}" "${mount.fsType}"
+    '') mounts);
+
 in
 
 {
@@ -131,8 +151,7 @@ in
           "/bigdisk".label = "bigdisk";
         }
       '';
-      type = types.loaOf types.optionSet;
-      options = [ fileSystemOpts ];
+      type = types.loaOf (types.submodule fileSystemOpts);
       description = ''
         The file systems to be mounted.  It must include an entry for
         the root directory (<literal>mountPoint = "/"</literal>).  Each
@@ -177,10 +196,14 @@ in
       { assertion = ! (fileSystems' ? "cycle");
         message = "The ‘fileSystems’ option can't be topologically sorted: mountpoint dependency path ${ls " -> " fileSystems'.cycle} loops to ${ls ", " fileSystems'.loops}";
       }
+      { assertion = all (x: !x.early || (x.label == null && !x.autoFormat && !x.autoResize)) fileSystems;
+        message = "Early filesystems don't support mounting by label, auto formatting and resizing";
+      }
     ];
 
     # Export for use in other modules
     system.build.fileSystems = fileSystems;
+    system.build.earlyMountScript = makeSpecialMounts (filter (fs: fs.early) fileSystems);
 
     boot.supportedFilesystems = map (fs: fs.fsType) fileSystems;
 
@@ -211,7 +234,7 @@ in
             + " " + (if skipCheck fs then "0" else
                      if fs.mountPoint == "/" then "1" else "2")
             + "\n"
-        ) fileSystems}
+        ) (filter (fs: !fs.early) fileSystems)}
 
         # Swap devices.
         ${flip concatMapStrings config.swapDevices (sw:
@@ -258,6 +281,16 @@ in
 
       in listToAttrs (map formatDevice (filter (fs: fs.autoFormat) fileSystems));
 
+    # Sync mount options with systemd's src/core/mount-setup.c: mount_table.
+    fileSystems = mapAttrs (n: fs: fs // { early = true; }) {
+      "/proc" = { fsType = "proc"; options = [ "nosuid" "noexec" "nodev" ]; };
+      "/sys" = { fsType = "sysfs"; options = [ "nosuid" "noexec" "nodev" ]; };
+      "/run" = { fsType = "tmpfs"; options = [ "nosuid" "nodev" "strictatime" "mode=755" "size=${config.boot.runSize}" ]; };
+      "/dev" = { fsType = "devtmpfs"; options = [ "nosuid" "strictatime" "mode=755" "size=${config.boot.devSize}" ]; };
+      "/dev/shm" = { fsType = "tmpfs"; options = [ "nosuid" "nodev" "strictatime" "mode=1777" "size=${config.boot.devShmSize}" ]; };
+      "/dev/pts" = { fsType = "devpts"; options = [ "nosuid" "noexec" "mode=620" "gid=${toString config.ids.gids.tty}" ]; };
+    };
+
   };
 
 }