I add that I placed iso image in a vfat partition. And after, in terminal: modprobe vfat mkdir /mnt/source mount -t vfat /dev/sd?? /mnt/source
I can see iso image there but when I try mounting it through a loop device: mount -o loop /mnt/source/image.iso /cdrom it fails so installation cannot go on. It seems this second need was already reported in 785512 bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=785512 -- -- Salutacions...Josep --