1 files changed, 27 insertions, 0 deletions
diff --git a/nixpkgs/nixos/lib/utils.nix b/nixpkgs/nixos/lib/utils.nix
new file mode 100644
index 000000000000..b68e55a40b90
--- /dev/null
+++ b/nixpkgs/nixos/lib/utils.nix
@@ -0,0 +1,27 @@
+pkgs: with pkgs.lib;
+
+rec {
+
+  # Check whenever fileSystem is needed for boot
+  fsNeededForBoot = fs: fs.neededForBoot
+                     || elem fs.mountPoint [ "/" "/nix" "/nix/store" "/var" "/var/log" "/var/lib" "/etc" ];
+
+  # Check whenever `b` depends on `a` as a fileSystem
+  fsBefore = a: b: a.mountPoint == b.device
+                || hasPrefix "${a.mountPoint}${optionalString (!(hasSuffix "/" a.mountPoint)) "/"}" b.mountPoint;
+
+  # Escape a path according to the systemd rules, e.g. /dev/xyzzy
+  # becomes dev-xyzzy.  FIXME: slow.
+  escapeSystemdPath = s:
+   replaceChars ["/" "-" " "] ["-" "\\x2d" "\\x20"]
+    (if hasPrefix "/" s then substring 1 (stringLength s) s else s);
+
+  # Returns a system path for a given shell package
+  toShellPath = shell:
+    if types.shellPackage.check shell then
+      "/run/current-system/sw${shell.shellPath}"
+    else if types.package.check shell then
+      throw "${shell} is not a shell package"
+    else
+      shell;
+}