[Libguestfs] [PATCH 2/2] v2v: ilnux: detect name of grub2-mkconfig

[Tomáš Golembiovský]

On Thu, 11 Aug 2016 11:51:20 +0200
Pino Toscano <ptoscano at redhat.com> wrote:

> On Thursday, 11 August 2016 00:35:55 CEST Tomáš Golembiovský wrote:
> > On Debian family of OSes Grub2 tools are prefixed with 'grub-', not with
> > 'grub2-'. We have to detect the correct name of the tool to use it.
> > 
> > Signed-off-by: Tomáš Golembiovský <tgolembi at redhat.com>
> > ---
> >  v2v/convert_linux.ml | 21 +++++++++++++++++++--
> >  1 file changed, 19 insertions(+), 2 deletions(-)
> > 
> > diff --git a/v2v/convert_linux.ml b/v2v/convert_linux.ml
> > index 103728b..1f5f12c 100644
> > --- a/v2v/convert_linux.ml
> > +++ b/v2v/convert_linux.ml
> > @@ -109,6 +109,23 @@ let rec convert ~keep_serial_console (g : G.guestfs) inspect source rcaps =
> >        Not_found ->
> >          error (f_"no grub1/grub-legacy or grub2 configuration file was found") in
> >  
> > +  let grub2_mkconfig_cmd =
> > +    if grub = `Grub2 then
> > +      try
> > +        (* Red Hat and Suse families *)
> > +        ignore (g#command [| "grub2-mkconfig"; "--version" |]);
> > +        "grub2-mkconfig"
> > +      with G.Error _ ->
> > +        try
> > +          (* Debian family *)
> > +          ignore (g#command [| "grub-mkconfig"; "--version" |]);
> > +          "grub-mkconfig"
> > +        with G.Error _ ->
> > +          error (f_"failed to find grub2-mkconfig binary (but Grub2 was detected on guest)")
> > +    else
> > +      ""
> > +  in  
> 
> Maybe it would be worth to put the elements in a list, and iterate
> using List.find:
> 
>   let elems = [ "grub2-mkconfig"; "grub-mkconfig" ] in
>   let elem =
>     try
>       List.find (
>         let e ->
>           try ignore (g#command [| e; "--version" |]); true
>           with G.Error _ -> false
>       ) elems
>     with Not_found ->
>       error "not found" in

Yes, we can do it that way.

> 
> Also, what I've seen usually done is checking for the existance of the
> executable, eg: if g#file_exists "/usr/sbin/grub2-mkconfig" then ...

I tried to avoid that, because I wasn't sure if the tool is always in
/usr/sbin (vs. e.g. in /sbin) on all supported guests. If you can
confirm it is always in /usr/sbin we can use g#file_exists. Also, even
if we cannot confirm that, we can enumerate multiple paths if we use
your method with list above.

> this way, even if requiring to specify the exact locations of the tools,
> would avoid ignoring a tool just because it cannot run for some reason,
> while we need to fail because of that.

I'm not sure I understand. I doubt you can find multiple versions of the
tool on single host. That means if the tool is not working the check
will fail, because it won't find any usable tool.


-- 
Tomáš Golembiovský <tgolembi at redhat.com>