[Libguestfs] [PATCH v3] 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 | 78 +++++++++++++++++++++++++++++-------------------
 1 file changed, 47 insertions(+), 31 deletions(-)

diff --git a/v2v/linux_bootloaders.ml b/v2v/linux_bootloaders.ml
index e03d22b..0c236e1 100644
--- a/v2v/linux_bootloaders.ml
+++ b/v2v/linux_bootloaders.ml
@@ -49,6 +49,14 @@ let remove_hd_prefix path =
 
 (* Grub1 (AKA grub-legacy) representation. *)
 class bootloader_grub1 (g : G.guestfs) inspect grub_config =
+  (* We expect Augeas to parse the grub_config file.  However
+   * the upstream lens only lists a subset of the possible
+   * locations for this file.  Therefore tell Augeas that
+   * grub_config is a grub file (this apparently doesn't affect
+   * Augeas if it already parsed the file).
+   *)
+  let () = g#aug_transform "grub" grub_config 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 = [
@@ -333,34 +341,42 @@ object (self)
     ignore (g#command [| grub2_mkconfig_cmd; "-o"; grub_config |])
 end
 
+(* 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 =
+  if String.is_suffix path "/grub.cfg" then
+    Some Grub2
+  else if String.is_suffix path "/grub.conf" ||
+          String.is_suffix path "/menu.lst" then
+    Some Grub1
+  else
+    None
+
+(* Where to start searching for bootloaders. *)
+let bootloader_mountpoint = function
+  | { i_firmware = I_BIOS } -> "/boot"
+  | { i_firmware = I_UEFI _ } -> "/boot/efi/EFI"
+
 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
+  let mp = bootloader_mountpoint inspect in
+  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
+
+  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
+
+  (match typ with
+   | Grub1 -> new bootloader_grub1
+   | Grub2 -> new bootloader_grub2) g inspect grub_config
-- 
2.9.3