You can do it with a really easy way :
Install the package syslinux
Put your usb key and do not mount it and do :
# isohybrid /path/to/file.iso
# dd if=/path/to/file.iso of=/dev/sdXstatus=progress
Une note conservée dans les archives. Les versions et commandes évoquées correspondent à sa date de publication.
You can do it with a really easy way :
Install the package syslinux
Put your usb key and do not mount it and do :
# isohybrid /path/to/file.iso
# dd if=/path/to/file.iso of=/dev/sdXstatus=progress