util-linux: split mount, login and swap utils into their own outputs

pkgs/os-specific/linux/systemd/default.nix

@@ -508,9 +508,10 @@ stdenv.mkDerivation (finalAttrs: {
     "-Dsysvinit-path="
     "-Dsysvrcnd-path="
 
-    "-Dsulogin-path=${util-linux}/bin/sulogin"
-    "-Dmount-path=${util-linux}/bin/mount"
-    "-Dumount-path=${util-linux}/bin/umount"
+    "-Dsulogin-path=${util-linux.login}/bin/sulogin"
+    "-Dnologin-path=${util-linux.login}/bin/nologin"
+    "-Dmount-path=${util-linux.mount}/bin/mount"
+    "-Dumount-path=${util-linux.mount}/bin/umount"
     "-Dcreate-log-dirs=false"
 
     # Use cgroupsv2. This is already the upstream default, but better be explicit.
@@ -561,8 +562,8 @@ stdenv.mkDerivation (finalAttrs: {
             "man/systemd-makefs@.service.xml"
           ];
         }
-        { search = "/sbin/swapon"; replacement = "${lib.getBin util-linux}/sbin/swapon"; where = [ "src/core/swap.c" "src/basic/unit-def.h" ]; }
-        { search = "/sbin/swapoff"; replacement = "${lib.getBin util-linux}/sbin/swapoff"; where = [ "src/core/swap.c" ]; }
+        { search = "/sbin/swapon"; replacement = "${util-linux.swap}/sbin/swapon"; where = [ "src/core/swap.c" "src/basic/unit-def.h" ]; }
+        { search = "/sbin/swapoff"; replacement = "${util-linux.swap}/sbin/swapoff"; where = [ "src/core/swap.c" ]; }
         {
           search = "/bin/echo";
           replacement = "${coreutils}/bin/echo";

pkgs/os-specific/linux/util-linux/default.nix

@@ -50,7 +50,12 @@ stdenv.mkDerivation rec {
     })
   ];
 
-  outputs = [ "bin" "dev" "out" "lib" "man" ];
+  # We separate some of the utilities into their own outputs. This
+  # allows putting together smaller systems depending on only part of
+  # the greater util-linux toolset.
+  # Compatibility is maintained by symlinking the binaries from the
+  # smaller outputs in the bin output.
+  outputs = [ "bin" "dev" "out" "lib" "man" "mount" "login" "swap" ];
   separateDebugInfo = true;
 
   postPatch = ''
@@ -106,6 +111,18 @@ stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   postInstall = ''
+    moveToOutput bin/mount "$mount"
+    moveToOutput bin/umount "$mount"
+    ln -svf "$mount/bin/"* $bin/bin/
+
+    moveToOutput sbin/nologin "$login"
+    moveToOutput sbin/sulogin "$login"
+    ln -svf "$login/bin/"* $bin/bin/
+
+    moveToOutput sbin/swapon "$swap"
+    moveToOutput sbin/swapoff "$swap"
+    ln -svf "$swap/bin/"* $bin/bin/
+
     installShellCompletion --bash bash-completion/*
   '';