Libguestfs - Aug 2015 - [PATCH v2] customize: Use setarch when running commands on i686 guest

v2: Fix problem when running multiple commands.

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
...

The use of a heredoc to solve quoting issues comes from:
http://stackoverflow.com/a/3435460

Thanks: Jan Sedlák for finding the solution.
---
 customize/customize_run.ml | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/customize/customize_run.ml b/customize/customize_run.ml
index 828c711..2283272 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 +70,18 @@ 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 <<\"__EOCMD\"
 %s
-" (quote logfile) env_vars cmd in
+__EOCMD
+" (quote logfile) env_vars setarch cmd in
 
     if verbose () then printf "running command:\n%s\n%!" cmd;
     try ignore (g#sh cmd)
-- 
2.5.0