Comment 10 for bug 1914587

The construction of the iso is buried in https://people.canonical.com/~ubuntu-archive/cd-build-logs/ubuntu-server/focal/daily-live-20210209.log, for ppc64el it seems to be:

/usr/bin/mkisofs -r -V Ubuntu-Server\ 20.04.2\ LTS\ ppc64 -o /srv/cdimage.ubuntu.com/scratch/ubuntu-server/focal/daily-live/debian-cd/ppc64el/focal-live-server-ppc64el.raw --netatalk -hfs -probe -map /srv/cdimage.ubuntu.com/debian-cd/data/hfs.map -chrp-boot -iso-level 4 -part -no-desktop -hfs-bless CD1/install -hfs-volid Ubuntu-Server_PPC64EL_focal -sort /srv/cdimage.ubuntu.com/scratch/ubuntu-server/focal/daily-live/tmp/focal-ppc64el/1.weights CD1

I don't know why we use mkisofs rather than xorriso for ppc64el. Maybe we should switch.

I proposed https://github.com/CanonicalLtd/subiquity/pull/892 to fail if -report_el_torito fails.