From owner-freebsd-xen@freebsd.org Wed Apr 12 04:34:25 2017 Return-Path: Delivered-To: freebsd-xen@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 642C1D3A644 for ; Wed, 12 Apr 2017 04:34:25 +0000 (UTC) (envelope-from 0100015b6070ce13-1ed22322-147b-4596-b049-bfb58e7b591e-000000@amazonses.com) Received: from a8-52.smtp-out.amazonses.com (a8-52.smtp-out.amazonses.com [54.240.8.52]) (using TLSv1 with cipher ECDHE-RSA-AES128-SHA (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 2A3FEC2F for ; Wed, 12 Apr 2017 04:34:25 +0000 (UTC) (envelope-from 0100015b6070ce13-1ed22322-147b-4596-b049-bfb58e7b591e-000000@amazonses.com) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=ae7m2yrxjw65l2cqdpjxuucyrvy564tn; d=tarsnap.com; t=1491971657; h=Subject:To:References:From:Reply-To:Message-ID:Date:MIME-Version:In-Reply-To:Content-Type:Content-Transfer-Encoding; bh=OIbNsX9lOIof4jp7uxrUQFYykbr+wdze1M/lls57iI4=; b=qYwTyesHbFCiamZChrN576r8KUYSjt/5L5JyyqukBk3Me1lpD1Ka9vOb+ofRmnj6 sjSjCOOYnfyAQXdhIHdWkwqLyBO0gS4le8Ot6Kw+I23y+ypG3Z2UElN7bdGCLxyowBF GHOWXehJeiEtXqbUK2onvlH0BA74VH+eT17Wohp8= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple; s=224i4yxa5dv7c2xz3womw6peuasteono; d=amazonses.com; t=1491971657; h=Subject:To:References:From:Reply-To:Message-ID:Date:MIME-Version:In-Reply-To:Content-Type:Content-Transfer-Encoding:Feedback-ID; bh=OIbNsX9lOIof4jp7uxrUQFYykbr+wdze1M/lls57iI4=; b=QOLngKdBAruHzKHvgHDFcMXtR/eWzB+uJXeczB1SlvtjChtHYXEyQ46ncmVWhkYq CLaJoJzZcMwoP6JEfH0KkYslOWA9ws7NnPQ/q+6Psa0mGq1wbiGqWdGYnOhrSYcLZYS P7jyD6RiarhvSxrQuexD4D0IvcJeJixd8KSiZ3fU= Subject: Re: amazon/xen... any way at all to pass a message/signal/semaphoere/morse-code to the boot loader? To: Julian Elischer , FreeBSD Lists , Toomas Soome , freebsd-cloud@freebsd.org References: From: Colin Percival Reply-To: freebsd-cloud@freebsd.org Message-ID: <0100015b6070ce13-1ed22322-147b-4596-b049-bfb58e7b591e-000000@email.amazonses.com> Date: Wed, 12 Apr 2017 04:34:17 +0000 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SES-Outgoing: 2017.04.12-54.240.8.52 Feedback-ID: 1.us-east-1.Lv9FVjaNvvR5llaqfLoOVbo2VxOELl7cjN0AOyXnPlk=:AmazonSES X-BeenThere: freebsd-xen@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussion of the freebsd port to xen - implementation and usage List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Apr 2017 04:34:25 -0000 [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? > 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...? -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid