Libguestfs - May 2017 - Re: [PATCH] v2v: bootloaders: search grub config for all distributions

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 | 80 ++++++++++++++++++++++++++++++------------------
 1 file changed, 50 insertions(+), 30 deletions(-)

diff --git a/v2v/linux_bootloaders.ml b/v2v/linux_bootloaders.ml
index cad72a829..33a6dc4e9 100644
--- a/v2v/linux_bootloaders.ml
+++ b/v2v/linux_bootloaders.ml
@@ -49,6 +49,13 @@ let remove_hd_prefix path  
 (* Grub1 (AKA grub-legacy) representation. *)
 class bootloader_grub1 (g : G.guestfs) inspect grub_config +  let () +  (*
Apply the "grub" lens if it is not handling the file
+   * already -- Augeas < 1.7.0 will error out otherwise.
+   *)
+  if g#aug_ls ("/files" ^ grub_config) = [||] then
+    g#aug_transform "grub" grub_config in
+
   (* Grub prefix?  Usually "/boot". *)
   let grub_prefix      let mounts = g#inspect_get_mountpoints inspect.i_root in
@@ -335,33 +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
+
+  let bl +    (match typ with
+     | Grub1 -> new bootloader_grub1 g inspect grub_config
+     | Grub2 -> new bootloader_grub2 g grub_config) in
+  debug "detected bootloader %s at %s" bl#name grub_config;
+  bl
-- 
2.11.0

[PATCH v7] - Sorry, forgot to add

On Tue, May 02, 2017 at 03:35:06PM +0300, Pavel Butsykin
wrote:
> 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>
Thanks - this is pushed.

Sorry it took a bit of time, I had to run all of the virt-v2v non-free
test cases to convince myself there were no corner cases that might
regress.  They passed fine.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org