diff --git a/daemon/inspect.ml b/daemon/inspect.ml
index fb75b4a6c..20217c025 100644
--- a/daemon/inspect.ml
+++ b/daemon/inspect.ml
@@ -335,6 +335,12 @@ and inspect_get_hostname root =
   | Some v -> v
   | None -> "unknown"
 
+and inspect_get_build_id root =
+  let root = search_for_root root in
+  match root.inspection_data.build_id with
+  | Some v -> v
+  | None -> "unknown"
+
 and inspect_get_windows_systemroot root =
   let root = search_for_root root in
   match root.inspection_data.windows_systemroot with
diff --git a/daemon/inspect_fs_unix.ml b/daemon/inspect_fs_unix.ml
index 8045ef0d4..811e23b18 100644
--- a/daemon/inspect_fs_unix.ml
+++ b/daemon/inspect_fs_unix.ml
@@ -96,6 +96,8 @@ let rec parse_os_release release_file data =
            data.product_name <- Some value
          else if key = "VERSION_ID" then
            parse_os_release_version_id value data
+         else if key = "BUILD_ID" then
+           data.build_id <- Some value
        ) values;
 
      (* If we haven't got all the fields, exit right away. *)
diff --git a/daemon/inspect_fs_windows.ml b/daemon/inspect_fs_windows.ml
index c4a05bc38..7bc5de7f7 100644
--- a/daemon/inspect_fs_windows.ml
+++ b/daemon/inspect_fs_windows.ml
@@ -263,6 +263,20 @@ and check_windows_software_registry software_hive data =
          with
            Not_found -> ()
         );
+
+        (* CurrentBuildNumber (build_id).
+         *
+         * In modern Windows, the "CurrentBuild" and "CurrentBuildNumber"
+         * keys are the same.  But in Windows XP, "CurrentBuild"
+         * contained something quite different.  So always use
+         * "CurrentBuildNumber".
+         *)
+        (try
+           let v = List.assoc "CurrentBuildNumber" values in
+           data.build_id <- Some (Hivex.value_string h v)
+         with
+           Not_found -> ()
+        );
       with
       | Not_found ->
          if verbose () then
diff --git a/daemon/inspect_types.ml b/daemon/inspect_types.ml
index 9395c51f9..328a2146b 100644
--- a/daemon/inspect_types.ml
+++ b/daemon/inspect_types.ml
@@ -48,6 +48,7 @@ and inspection_data = {
   mutable version : version option;
   mutable arch : string option;
   mutable hostname : string option;
+  mutable build_id : string option;
   mutable fstab : fstab_entry list;
   mutable windows_systemroot : string option;
   mutable windows_software_hive : string option;
@@ -167,6 +168,8 @@ and string_of_inspection_data data =
              data.arch;
   Option.may (fun v -> bpf "    hostname: %s\n" v)
              data.hostname;
+  Option.may (fun v -> bpf "    build ID: %s\n" v)
+             data.build_id;
   if data.fstab <> [] then (
     let v = List.map (
       fun (a, b) -> sprintf "(%s, %s)" (Mountable.to_string a) b
@@ -272,6 +275,7 @@ let null_inspection_data = {
   version = None;
   arch = None;
   hostname = None;
+  build_id = None;
   fstab = [];
   windows_systemroot = None;
   windows_software_hive = None;
@@ -294,6 +298,7 @@ let merge_inspection_data child parent =
   parent.version <-         merge child.version parent.version;
   parent.arch <-            merge child.arch parent.arch;
   parent.hostname <-        merge child.hostname parent.hostname;
+  parent.build_id <-        merge child.build_id parent.build_id;
   parent.fstab <-           child.fstab @ parent.fstab;
   parent.windows_systemroot <-
     merge child.windows_systemroot parent.windows_systemroot;
diff --git a/daemon/inspect_types.mli b/daemon/inspect_types.mli
index 29c76e8ab..05a3ffd4e 100644
--- a/daemon/inspect_types.mli
+++ b/daemon/inspect_types.mli
@@ -51,6 +51,7 @@ and inspection_data = {
   mutable version : version option;
   mutable arch : string option;
   mutable hostname : string option;
+  mutable build_id : string option;
   mutable fstab : fstab_entry list;
   mutable windows_systemroot : string option;
   mutable windows_software_hive : string option;
diff --git a/generator/actions_inspection.ml b/generator/actions_inspection.ml
index f8b744993..70de22ec0 100644
--- a/generator/actions_inspection.ml
+++ b/generator/actions_inspection.ml
@@ -529,6 +529,25 @@ hive is a valid Windows Registry hive.
 
 You can use C<guestfs_hivex_open> to read or write to the hive.
 
+Please read L<guestfs(3)/INSPECTION> for more details." };
+
+  { defaults with
+    name = "inspect_get_build_id"; added = (1, 49, 8);
+    style = RString (RPlainString, "buildid"), [String (Mountable, "root")], [];
+    impl = OCaml "Inspect.inspect_get_build_id";
+    shortdesc = "get the system build ID";
+    longdesc = "\
+This returns the build ID of the system, or the string
+C<\"unknown\"> if the system does not have a build ID.
+
+For Windows, this gets the build number.  Although it is
+returned as a string, it is (so far) always a number.  See
+L<https://en.wikipedia.org/wiki/List_of_Microsoft_Windows_versions>
+for some possible values.
+
+For Linux, this returns the C<BUILD_ID> string from
+F</etc/os-release>, although this is not often used.
+
 Please read L<guestfs(3)/INSPECTION> for more details." };
 
   { defaults with
diff --git a/generator/proc_nr.ml b/generator/proc_nr.ml
index edd9bd99d..0f17b1c06 100644
--- a/generator/proc_nr.ml
+++ b/generator/proc_nr.ml
@@ -514,7 +514,8 @@ let proc_nr = [
 509, "cryptsetup_close";
 510, "internal_list_rpm_applications";
 511, "internal_readdir";
-512, "clevis_luks_unlock"
+512, "clevis_luks_unlock";
+513, "inspect_get_build_id";
 ]
 
 (* End of list.  If adding a new entry, add it at the end of the list
diff --git a/lib/MAX_PROC_NR b/lib/MAX_PROC_NR
index 4d0e90cbc..31cf34b8d 100644
--- a/lib/MAX_PROC_NR
+++ b/lib/MAX_PROC_NR
@@ -1 +1 @@
-512
+513