To make matters even more interesting: as a sort of variation of (A) an option exists to create a kind of "companion" initrd. That is described in this wiki page. In which case an additional initrd gets created, and the boot loader is instructed to extract those multiple archives into RAM at boot time. Choosing this option makes probably only sense when one wants to add to the Core system and not when a file of the Core system is meant to be changed. As in this latter case you would depend on the order of the extractions to end up with the expected result, I for one would not want to take a bet on this.
After an intense search of documentation didn't lead to any clue about the subject, I addressed a syslinux dev on IRC.
He had to do quite some testing with various variables, to come to the following conclusions:
- With older versions (e.g. 3.61 which is included in base of TC 2.10) multiple initrd's appear to be loaded in the reverse of order specified, but extracted in the order specified
- With recent versions multiple initrd's get loaded and extracted in the order specified
Quintessence: It should be predictable that multiple initrd's always get
extracted in the order specified, regardless of variables.