On 29/09/2013 19:43, Tanstaafl wrote: > On 2013-09-28 6:46 PM, Neil Bothwick <n...@digimed.co.uk> 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.mckin...@gmail.com
