From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lists.gentoo.org (pigeon.gentoo.org [208.92.234.80]) by finch.gentoo.org (Postfix) with ESMTP id 60C4E1381F3 for ; Sun, 29 Sep 2013 19:59:04 +0000 (UTC) Received: from pigeon.gentoo.org (localhost [127.0.0.1]) by pigeon.gentoo.org (Postfix) with SMTP id C7375E0F7E; Sun, 29 Sep 2013 19:58:58 +0000 (UTC) Received: from mail-wi0-f171.google.com (mail-wi0-f171.google.com [209.85.212.171]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by pigeon.gentoo.org (Postfix) with ESMTPS id 8912BE0F39 for ; Sun, 29 Sep 2013 19:58:57 +0000 (UTC) Received: by mail-wi0-f171.google.com with SMTP id hm2so2893151wib.4 for ; Sun, 29 Sep 2013 12:58:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=4Hpo3lO5IrIPkhAkn8ZrDX4K1EA1gKzapo9liWAKDCE=; b=BQpixnhgwl9Tofr25Sp+9KWL2yS1mYAbIRk+fHsjEi1LU2lWnq/BRzZ0BBgdA3/0ek 19m69RbXEF6th0TsblUOmxK0JNwpjPtW69CxGibUEyDxFTzrzSwrtBKF6pePpTBJl/iq 2OmY9LSJSNHBsgDmlOqneR8z+I28BRId4oS8NjqcUiBH95YVM9JQErn7jRKR9Sw70XLH AouXwph2sILasi4EAWJHcUlkM33/zGlRfko3pGOTPkX0BOLmWNyz0VwAg0N3W/joMbLn yqSpH/yi2/0N4MS569/06rnWS5Zik5v6Xb3Mbe8VGH82Buo877CNnJXMsyfu/16IwKm1 3AHA== X-Received: by 10.180.20.163 with SMTP id o3mr11124932wie.1.1380484736185; Sun, 29 Sep 2013 12:58:56 -0700 (PDT) Received: from [172.20.0.40] (196-210-102-121.dynamic.isadsl.co.za. [196.210.102.121]) by mx.google.com with ESMTPSA id ev4sm18828373wib.7.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sun, 29 Sep 2013 12:58:55 -0700 (PDT) Message-ID: <52488571.9070709@gmail.com> Date: Sun, 29 Sep 2013 21:54:25 +0200 From: Alan McKinnon User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.0 Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-user@lists.gentoo.org Reply-to: gentoo-user@lists.gentoo.org MIME-Version: 1.0 To: gentoo-user@lists.gentoo.org Subject: Re: [gentoo-user] separate / and /usr to require initramfs 2013-11-01 References: <20130927222109.GD23408@server> <5246079E.7090406@gmail.com> <20130927223916.GE23408@server> <52460D42.2080109@gmail.com> <20130928003220.GF23408@server> <20130928160159.GA4247@linux1> <5247128D.3030801@gmail.com> <20130928205308.547335bf@digimed.co.uk> <5247550D.5010200@gmail.com> <20130928234621.57754558@digimed.co.uk> <524866AE.4060908@libertytrek.org> In-Reply-To: <524866AE.4060908@libertytrek.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Archives-Salt: 4ffc90fb-d409-4574-a747-f4af4c4ebf70 X-Archives-Hash: 81000573b95bcd017268914e7d4170e9 On 29/09/2013 19:43, Tanstaafl wrote: > On 2013-09-28 6:46 PM, Neil Bothwick wrote: >> Except you can never break Gentoo with a kernel update because, unlike >> some other distros, installing a new kernel does not uninstall the >> previous one. No matter how badly wrng a kernel update goes, you can >> always hit reset then select the old one from the GRUB menu - >> reinstallation doesn't come into it. > > My understanding is that this is not true, and that a USERLAND update > (LVM2, which I use, among them) can cause breakage that will cause the > CURRENT kernel+initramfs to no longer boot. > > Is my understanding flawed? No, this can happen in theory. It's quite simple to describe in somewhat abstract terms: Imagine for example that LVM makes a backwards-incompatible change to it's metadata. You are warned about this and take care to update your kernel so that it can deal with the new metadata by including support for both formats. And you forget to update the initramfs. Reboot. Oops. This is merely highly inconvenient, not the end of the world. Download a very recent rescue disk on another computer and boot with that to effect the repair. Then leave work and make your local publican's day whilst you vent your fury yet again Point is, this is not a situation unique to kernels, userlands and initramfs. That kind of error can occur in so many different ways (eg deploy a seriously broken linker and loader, or simply uninstall bash on a RHEL4 host), it's just that when it happens in the circumstances you ask about, it's one of the most inconvenient errors in a huge list. This is why we sysadmins have jobs - we are supposed to have subtantial clue and be able to predict and avoid such goofs. > Totally side question: Anyone ever hear Linus' opinion of an initramfs > being required to boot a system? Never read it myself, but I'll hazard a guess: He detests it with a passion calling it a grotesque hack, but tolerates it because binary distros need it and no-one has come up with something better (i.e. it sucks less)? -- Alan McKinnon alan.mckinnon@gmail.com