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To: Colin Percival <cperciva@FreeBSD.org>,
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From: Julian Elischer <julian@freebsd.org>
Subject: amazon/xen... any way at all to pass a
 message/signal/semaphoere/morse-code to the boot loader?
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Date: Wed, 12 Apr 2017 12:03:30 +0800
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In Amazon ec2 they have no console access (though I heard rumors that 
it was available I have not seen any sign of it) so I'd like to put a 
"recovery partition" into an AMI.
The trick is how to convince it to boot to that instead of the regular 
action.


The ideal thing would be if there was  way to 'influence' one of the 
smbios values in some way, and have the boot code see it, but I'm open 
to any suggestions.
I really need only 1 bit of information to get through.

Possibilties include "changing the VM to have only 2G of ram" (we'd 
never do that in a real machine).
or maybe temporarily removing all the disks other than the root drive? 
Almost anything I could do to signal the boot code to behave differently.