bug#33639: ISO installer image is broken on i686

["pelzflorian (Florian Pelz)" <pelzflorian@pelzflorian.de>]

I have what may be the same problem on my x86_64 machine building for
x86_64 when creating an ISO install image by running

guix system disk-image --file-system-type=iso9660 gnu/system/install.scm

Since commit 45c0d1d790f01ebc020fc4b2787a6abcdaa3f383 increased the
RAM for the VM that builds the iso image from 256 to 512, iso files
consistently were corrupt, until I added an lstat call, see below.  On
a second and third attempt to build with lstat I got a corrupt image
again.  Guix install iso files I tested from before that commit were
fine.


florian@florianmacbook ~$ fdisk /gnu/store/4nrwajlpab4s8pdph4d77ww7716sa3ir-image.iso
[…]
GPT PMBR size mismatch (3231107 != 3200391) will be corrected by write.

xorriso is sorry exactly like in Ludo’s message from December 06.  The
numbers reported and file sizes are not consistent between corrupt
rebuilds.



On Fri, Dec 21, 2018 at 10:42:14PM +0100, Thomas Schmitt wrote:
> […]
> Next time you make an ISO, retrieve the last size messages of xorriso:
>   ISO image produced: 500069 sectors
>   Written to medium : 500069 sectors at LBA 0

For the corrupt iso with lstat call:

ISO image produced: 807777 sectors
Written to medium : 807777 sectors at LBA 0



> the new message about the ISO image file size in bytes,

Within the VM lstat consistently reports 1654327296 for non-corrupt
and corrupt images alike.



> and the size of
> the ISO image file size when it is finally ready for exposure in the web.
>

ls -l on the result reports 1638600704.

On the non-corrupt image after adding the lstat call, both lstat
within the VM and ls -l outside the VM print the same size: 1654327296
in this case, i.e. the same as lstat reported on the corrupt images
within the VM.


(To be precise, for lstat I added the following local git commit to my
copy of the Guix repo at the end of the G-expression executed by the
VM:

diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index db9b1707d7..18ccb8970e 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -309,7 +309,8 @@ INPUTS is a list of inputs (as for packages)."
                                  #:closures graphs
                                  #:volume-id #$file-system-label
                                  #:volume-uuid #$(and=> file-system-uuid
-                                                        uuid-bytevector))))))
+                                                        uuid-bytevector))
+             (error (lstat "/xchg/guixsd.iso"))))))
    #:system system
 
    ;; Keep a local file system for /tmp so that we can populate it directly as



and then reconfigured the system after customizing the guix package to
use said commit and disabling tests on the guix package.  This
reported an lstat Scheme object as an error.  Note that the error
procedure does not cause a failed build.)

Regards,
Florian