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Using efi image on USB stick

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Using efi image on USB stick
Date: Mon, 17 May 2010 23:48:12 +0200
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Thanks to Seth Goldberg's and Jordan Uggla's testing it was discovered
how to make same iso bootable on EFI as both cdrom and usb stick. For
this it's needed in addition to el-torito to add a partition table with
a partition type 0xef pointing to the EFI image. What do you think the
best way to make it work with protective partition? Perhaps we should
have 3 partitions: protective1, EFI image, protective2. Perhaps we'll
need to have a fat partition with a stadard FAT partition type for
i386-ieee1275 (pure speculation, nothing checked yet). And MBR has space
only for 4 entries. I see following possibilities for this case:
1) Forcing FAT partitions to follow each other. It will probably be
tricky to implement and will mainly offset the problem
2) Leaving some space unprotected. Not good because it won't be possible
to safely add partitions to stick after DD'ing
3) Using GPT. Tricky because of backup GPT copy at disk end and doesn't
solve all the problems.
4) Using extened partition. IMHO it's the best way. We can have one
extended partition spanning accross the whole iso (marked as bootable to
workaround bugs in some BIOSes).  EBR will be placed into 2 sector which
is currently occupied by kernel.img but kernel.img can be moved anywhere
on iso9660. This way we have unlimited number of partitions available
for usage and leace the user 3 primary slots and unlimited number of
secondary partitions.

Vladimir 'φ-coder/phcoder' Serbinenko

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