From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <390F5449.5C1238EC@t-online.de> Date: Wed, 03 May 2000 00:18:49 +0200 From: Heinz Mauelshagen MIME-Version: 1.0 Subject: Re: [linux-lvm] SuSE/LVM boot problem References: <20000502052139.AAA12301@quartz.nbnet.nb.ca@Lxxxx.nbtel.nb.ca> <200005020951.LAA07870@e35.marxmeier.com> <20000502114113.C1608@archimedes.suse.com> <20000502232221.A20803@gondor.com> Content-Transfer-Encoding: 7bit Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" To: Jan Niehusmann Cc: dgould@suse.com, linux-lvm@msede.com Jan Niehusmann wrote: > > On this topic, what is needed to make lvm work for both / and /boot with > > full lilo support? I think it somewhat limits the utility of lvm not to > > be able to make a fully lvm system, and might be tempted to do some of > > the heavy lifting if it is not too gruesome. > > As lilo doesn't parse filesystems, it has to know the sector numbers of > the disk blocks that contain the kernel (and the second stage boot loader). > > I can imagine two ways to make lilo work with lvm: > > 1) at install time (when you run /sbin/lilo), lilo maps the logical (lvm) > locations to physical locations and writes these to the boot block. The boot > code doesn't need to be changed. > > 2) lilo writes logical locations to the boot block (trivial). The boot > code needs to understand lvm. > > Option 2 is probably very difficult to do, as it requires to implement > lvm handling in 16 bit code. Only read-only access is needed, but still, > it's probably a major project. > > Option 1 is way easier to implement, but has one big disadvantage: Whenever > you move physical extents, you have to re-run lilo. > > Both ways, you may end up with the kernel (or parts of it) moved to > a drive that's not accessible by lilo. (while the 1024-cylinder-limit > is gone, there are still drives that are accessible by linux but not by > the bios, for example scsi drives on a controller without bios) > > So, while I think it's fairly easy to make booting from lvm possible, there > are problems, and I don't know a solution for some of them. Actually some of them are not solvable at all :-{( LVM actually could try to deal with BIOS constraints but this would be a real mess regarding multiple platforms. IMHO it's not worth to put root on a logical volume because of the above mentioned problems and because of the fact, that a root filesystem of 300MB is only a fraction of a typical disks size of today and that it is big enough and therefore never has to be resized. BTW: all of the commercial solutions i'm aware of just 'fake' root in a logical volume to eanble mirroring. This can be done in Linux with MD anyway. Heinz