[Libguestfs] [PATCH] v2v: bootloaders: search grub config for all distributions

[Pavel Butsykin]

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>
---
 v2v/linux_bootloaders.ml | 56 +++++++++++++++++++++++++++++-------------------
 1 file changed, 34 insertions(+), 22 deletions(-)

diff --git a/v2v/linux_bootloaders.ml b/v2v/linux_bootloaders.ml
index e03d22b..210c273 100644
--- a/v2v/linux_bootloaders.ml
+++ b/v2v/linux_bootloaders.ml
@@ -335,32 +335,44 @@ 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;
+    let grub_configs = [
+      "grub.cfg", Grub2;
+      "grub.conf", Grub1;
+      "menu.lst", Grub1;
     ] in
-    let locations =
+
+    let boot_location =
       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
+      | I_BIOS -> "/boot/"
+      | I_UEFI _ -> "/boot/efi/EFI/"
+    in
+
+    let rec find_grub dirs configs =
+      let rec config_check dir configs =
+        match configs with
+        | [] -> None
+        | (config, typ) :: configs ->
+          let cfg_path = boot_location ^ dir ^ "/" ^ config in
+          if g#is_file ~followsymlinks:true cfg_path then (
+            Some (cfg_path, typ)
+          ) else config_check dir configs;
+      in
+      match dirs with
+      | [] -> error (f_"no bootloader detected")
+      | dir :: dirs ->
+        let res = config_check dir configs in
+        match res with
+        | None -> find_grub dirs configs
+        | Some (cfg_path, typ) -> cfg_path, typ
+    in
+
+  find_grub (Array.to_list (g#ls boot_location)) grub_configs 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";
-
+    (match inspect.i_firmware with
+    | I_BIOS -> ()
+    | I_UEFI _ -> g#aug_transform "grub" config_file
+    );
     new bootloader_grub1 g inspect config_file
   | Grub2 -> new bootloader_grub2 g config_file
-- 
2.8.3