Hi I am just thinking of one more problem that turned up. You suppose that I am running a RAID1 as you say I should install the boot-image of lilo to my root partition because Install-Mbr checks for it there. My problem: My Root-Partition is a RAID5. I would like to boot from a RAID1 and get my RAID5 going from there. Any hints? Zeno On Tue, 05 Oct 2004 13:08:19 +0400 Michael Tokarev <mjt@xxxxxxxxxx> wrote: > [I'm getting quite some questions similar to this > one -- so instead of replying to every and each, > I'm posting to linux-raid@, to be able to refer to > this post in the future... ;)] > > Zeno R.R. Davatz wrote: > > Hi! > > > > I am just reading a post of yours regarding using 'install-mbr' for linux-raid. > > > > Something I do not understand about the post: > > http://lists.debian.org/debian-testing/2004/04/msg00054.html > > > > is following: > > "mark your boot raid partitions active...". What do you mean by that? > > Set the partitions (single partition on every disk) where your root raid > device resides to be active with fdisk. > > > Do you mean to mark all the first partitions of all the disks /dev/sd[abcd]1 as boot with fdisk? > > Not necessary first ones, but it is simpler to have your root fs on > first partition. Again, it is the root-raid partition that should > be active. > > > In that case I would have to do install-mbr /dev/md0 --force > > No, you would have to use boot=/dev/md0 in your lilo.conf, > and install-mbr /dev/sd[abcd]1. > > > Is that correct? > > Basically, the scenario is as follows. > > Standard mbr (master boot record) from mbr package (note lilo also > have it, see lilo -M) is installed into standard place (where BIOS > will expect it to be) into all your disks once (don't forget to > install the same mbr when you plug new disk). The mbr code (it > resides on the first sector of the disk) works by reading partition > table, finding partition marked as "active" (or "boot" -- the same > flag but different terminology), loading boot record from that > partition and executing it. Mbr code is stable and you don't have > to change it -- the first sector of your disks will never change. > In contrast, you will do eg kernel upgrades and similar stuff, > for which lilo boot tables needs to be refreshed, and that should > be done on all disks (to be able to boot off any disk in case > first one fails). For this to work, you set up lilo to write > it's boot record into the device where your root filesystem is -- > it is raid1 array created off all active (boot) partitions of > all your disks. Lilo writes boot record into the beginning of > md0, and raid code propagates that boot record into your disks, > all of them -- remember, md0 is composed of active partitions > on all your disks -- this is exactly the place where mbr code > will look for the bootloader. > > So, you have the same mbr code on all your disks (installed > once when you configure each disk), and "second-stage" boot > record, installed by lilo into md0 and again propagated to > all disks (into active or boot partition of each), which will > be loaded by mbr -- this boot record will be updated -- on > all disks -- when you re-run lilo. In case any disk fails, > you have the same boot code and sequence on every other disk, > so you could boot off any working, non-failed disk. > > But be warned -- boot (active) partition on every disk should > be at the exactly same place, or else file offsets written by > lilo will be valid for one disk but not valid for other. > > /mjt > -- Mit freundlichen Grüssen / best regards Zeno Davatz Verkauf & Akquisition +41 1 350 85 86 www.ywesee.com > intellectual capital connected > www.oddb.org - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
