Date: Wed, 12 Apr 2017 09:09:45 +0300 From: Toomas Soome <tsoome@me.com> To: Julian Elischer <julian@freebsd.org> Cc: freebsd-cloud@freebsd.org, FreeBSD Lists <freebsd-xen@freebsd.org> Subject: Re: amazon/xen... any way at all to pass a message/signal/semaphoere/morse-code to the boot loader? Message-ID: <3A0FDF0B-B3CC-4CB7-AF9F-DC7CB60A6B5A@me.com> In-Reply-To: <6f1c694d-1bb7-cdcc-daed-fd2e25dc2a28@freebsd.org> References: <bf761b5c-63ad-bb14-4a9b-4e1fedced5bd@freebsd.org> <0100015b6070d24d-a23d7d90-11c0-4065-9bd0-0fc71b5874d6-000000@email.amazonses.com> <6f1c694d-1bb7-cdcc-daed-fd2e25dc2a28@freebsd.org>
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> On 12. apr 2017, at 9:04, Julian Elischer <julian@freebsd.org> wrote: > > On 12/4/17 12:34 pm, Colin Percival wrote: >> [CCing freebsd-cloud, which is the right place for discussions of FreeBSD/EC2] >> >> On 04/11/17 21:03, Julian Elischer wrote: >>> 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. >> Can you get what you want via gptboot's support for selecting the partition >> to boot via "bootonce" and "bootme" flags? > not if you can't get onto to the machine. > When I talk about a recovery partition I mean it in the same way that apple means it.. > "system won't boot? press the power button and hold down the 'option' key. > it will give you the option to boot to a recovery mode" > (* actually I can't remember the keys but you get the idea..) > > in our case we would like to be able to recover a customer's AMI by giving a simple set of instructions over the phone. > We can assume they know how to get into the amazon menus, but we would like to not have to assume much more. > >> >>> 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. >> I don't think adding/removing disks will be useful, since the extra disks will >> be Xen blkfront devices; AFAIK the boot loader doesn't know anything about >> these. (The boot device is also a blkfront device but gets ATA emulation for >> the benefit of boot loaders.) >> >> Maybe you can repurpose some of the logic used for booting over NFS? I've >> never heard of people booting over NFS when the initial bootstrap comes from >> disk rather than PXE, but I assume it's possible...? > > Oh I've done it, in the past but you still have the same issue.. > how do you signal the boot code to do this? > > (does an AMI have a bios capable of doing network operations?) I was thinking > about whether we could add a really simple xn driver into the bootcode to allow > us to have an console of sorts (accessible from an adjacent machine only??) > > > basically you want what zfsbootcfg does but in reverse — with fallback to recovery… rgds, toomas
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