[Libguestfs] [PATCH v4 1/2] v2v: bootloaders: search grub config for all distributions

[Richard W.M. Jones]

From: Pavel Butsykin <pbutsykin at virtuozzo.com>

This patch improves the search of grub config on EFI partition. This
means that the config will be found not only for rhel but also for
many other distributions.  Tests were performed on the following
distributions: centos, fedora, ubuntu, suse. In all cases, the config
path was /boot/efi/EFI/*distname*/grub.cfg

The main purpose of the patch is to improve support for converting of
vm with UEFI for most distributions. Unfortunately this patch does not
solve the problem for all distributions, for example Debian does not
store grub config on the EFI partition, therefore for such
distributions another solution is necessary.

Signed-off-by: Pavel Butsykin <pbutsykin at virtuozzo.com>
Signed-off-by: Richard W.M. Jones <rjones at redhat.com>
---
 v2v/linux_bootloaders.ml | 83 ++++++++++++++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 31 deletions(-)

diff --git a/v2v/linux_bootloaders.ml b/v2v/linux_bootloaders.ml
index e03d22b..9160dcc 100644
--- a/v2v/linux_bootloaders.ml
+++ b/v2v/linux_bootloaders.ml
@@ -42,6 +42,10 @@ type bootloader_type =
   | Grub1
   | Grub2
 
+let string_of_bootloader_type = function
+  | Grub1 -> "Grub1"
+  | Grub2 -> "Grub2"
+
 (* Helper function for SUSE: remove (hdX,X) prefix from a path. *)
 let remove_hd_prefix path =
   let rex = Str.regexp "^(hd.*)\\(.*\\)" in
@@ -49,6 +53,10 @@ let remove_hd_prefix path =
 
 (* Grub1 (AKA grub-legacy) representation. *)
 class bootloader_grub1 (g : G.guestfs) inspect grub_config =
+  let () =
+    if grub_config = "/boot/efi/EFI/redhat/grub.conf" then
+      g#aug_transform "grub" "/boot/efi/EFI/redhat/grub.conf" in
+
   (* Grub prefix?  Usually "/boot". *)
   let grub_prefix =
     let mounts = g#inspect_get_mountpoints inspect.i_root in
@@ -191,7 +199,7 @@ type default_kernel_method =
   | MethodNone  (** No known way. *)
 
 (* Grub2 representation. *)
-class bootloader_grub2 (g : G.guestfs) grub_config =
+class bootloader_grub2 (g : G.guestfs) inspect grub_config =
 
   let grub2_mkconfig_cmd =
     let elems = [
@@ -334,33 +342,46 @@ object (self)
 end
 
 let detect_bootloader (g : G.guestfs) inspect =
-  let config_file, typ =
-    let locations = [
-      "/boot/grub2/grub.cfg", Grub2;
-      "/boot/grub/grub.cfg", Grub2;
-      "/boot/grub/menu.lst", Grub1;
-      "/boot/grub/grub.conf", Grub1;
-    ] in
-    let locations =
-      match inspect.i_firmware with
-      | I_UEFI _ ->
-        [
-          "/boot/efi/EFI/redhat/grub.cfg", Grub2;
-          "/boot/efi/EFI/redhat/grub.conf", Grub1;
-        ] @ locations
-      | I_BIOS -> locations in
-    try
-      List.find (
-        fun (config_file, _) -> g#is_file ~followsymlinks:true config_file
-      ) locations
-    with
-      Not_found ->
-        error (f_"no bootloader detected") in
-
-  match typ with
-  | Grub1 ->
-    if config_file = "/boot/efi/EFI/redhat/grub.conf" then
-      g#aug_transform "grub" "/boot/efi/EFI/redhat/grub.conf";
-
-    new bootloader_grub1 g inspect config_file
-  | Grub2 -> new bootloader_grub2 g config_file
+  (* Where to start searching for bootloaders. *)
+  let mp =
+    match inspect.i_firmware with
+    | I_BIOS -> "/boot"
+    | I_UEFI _ -> "/boot/efi/EFI" in
+
+  (* Find all paths below the mountpoint, then filter them to find
+   * the grub config file.
+   *)
+  let paths =
+    try List.map ((^) mp) (Array.to_list (g#find mp))
+    with G.Error msg ->
+      error (f_"could not find bootloader mount point (%s): %s") mp msg in
+
+  (* We can determine if the bootloader config file is grub 1 or
+   * grub 2 just by looking at the filename.
+   *)
+  let bootloader_type_of_filename path =
+    match last_part_of path '/' with
+    | Some "grub.cfg" -> Some Grub2
+    | Some ("grub.conf" | "menu.lst") -> Some Grub1
+    | Some _
+    | None -> None
+  in
+
+  let grub_config, typ =
+    let rec loop = function
+      | [] -> error (f_"no bootloader detected")
+      | path :: paths ->
+         match bootloader_type_of_filename path with
+         | None -> loop paths
+         | Some typ ->
+            if not (g#is_file ~followsymlinks:true path) then loop paths
+            else path, typ
+    in
+    loop paths in
+
+  debug "detected bootloader %s at %s"
+        (string_of_bootloader_type typ) grub_config;
+
+  (match typ with
+   | Grub1 -> new bootloader_grub1
+   | Grub2 -> new bootloader_grub2) g inspect grub_config
-- 
2.9.3