boot error with backport jessie

[David Ansart <dansart@utec-tic.org>]

Hi

I have a problem and after a lot of search I don't find solution.

I use "Live Build" since 7 years to create "Live Raizo" where stable and 
backport have the same preference.

Since Septembre, iso is created but it don't boot.

I use live-build 4.0.3-1 (I believe to have tested live-build 5.x with 
the same result)

Here is an example of configuration :
>-------------------------------------------------------------
lb config noauto --distribution jessie --binary-images iso-hybrid 
--architectures amd64 --linux-flavours amd64 \
--archive-areas "main contrib" --apt-indices false --backports true 
--updates true \
--memtest memtest86+ \
--mirror-bootstrap http://ftp.fr.debian.org/debian/ --mirror-binary 
http://ftp.fr.debian.org/debian/ \
--bootappend-live "boot=live components locales=en_US.UTF-8 
hostname=minimal \
username=user noautologin"

cat /dev/null > config/package-lists/my.list.chroot
echo task-english >> config/package-lists/my.list.chroot
echo task-ssh-server >> config/package-lists/my.list.chroot

echo '! Packages Priority standard' > 
config/package-lists/standard.list.chroot

cat > config/archives/backport.pref.chroot <<EOF
Package: *
Pin: release n=jessie
Pin-Priority: 500

Package: *
Pin: release n=jessie-backports
Pin-Priority: 500
EOF
>-------------------------------------------------------------

When it boot, it stop into initramfs with error message :
mount: mounting aufs on /root/ failed: no such failed

Could you help me : what package is absent or outdated ? which option 
must I add or change ?

Thanks

David