[Libguestfs] [PATCH] customize: Use setarch when running commands on i686 guest (RHBZ#1256405).

[Richard W.M. Jones]

On Thu, Aug 27, 2015 at 05:32:31PM +0100, Richard W.M. Jones wrote:
> When running (eg) dnf on a 32 bit i686 guest when the host is 64 bit
> x86_64, dnf believes it is running on a 64 bit machine and so tries to
> install x86_64 packages.  We can 'trick' dnf into believing it's a 32
> bit machine using the setarch program.
> 
> $ virt-builder fedora-22 --arch i686 --install 'gperf'
> ...
> [  27.4] Installing packages: gperf
> ...
> Running transaction test
> Error: Transaction check error:
>   package libgcc-5.1.1-4.fc22.x86_64 is intended for a different architecture
> ...
> 
> Thanks: Jan Sedlák for finding the solution.
> ---
>  customize/customize_run.ml | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/customize/customize_run.ml b/customize/customize_run.ml
> index 828c711..2a4c71e 100644
> --- a/customize/customize_run.ml
> +++ b/customize/customize_run.ml
> @@ -59,6 +59,7 @@ let run (g : Guestfs.guestfs) root (ops : ops) =
>       * - Pass environment variables through from the host.
>       * - Send stdout and stderr to a log file so we capture all output
>       *   in error messages.
> +     * - Use setarch when running x86_64 host + i686 guest.
>       * Also catch errors and dump the log file completely on error.
>       *)
>      let env_vars =
> @@ -69,11 +70,16 @@ let run (g : Guestfs.guestfs) root (ops : ops) =
>        ) [ "http_proxy"; "https_proxy"; "ftp_proxy"; "no_proxy" ] in
>      let env_vars = String.concat "\n" env_vars ^ "\n" in
>  
> +    let setarch =
> +      match Config.host_cpu, guest_arch with
> +      | "x86_64", ("i386"|"i486"|"i586"|"i686") -> "setarch i686"
> +      | _ -> "" in
> +
>      let cmd = sprintf "\
>  exec >>%s 2>&1
>  %s
> -%s
> -" (quote logfile) env_vars cmd in
> +%s %s
> +" (quote logfile) env_vars setarch cmd in

Unfortunately this doesn't work if the 'cmd' is actually
multiple commands.  For example if the command was:

  uname -m ; uname -m

then this would be turned into:

  setarch i686 uname -m ; uname -m

and that would print:

  i686
  x86_64

It's tricky because setarch always wants to create a new shell.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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