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Bug#353679: linux-image-2.6.15-1-686 can't boot from partitioned RAID1 (partitions not discovered)



On Mon, Feb 20, 2006 at 10:43:20AM +0100, Helge Hafting wrote:
> 
> 
> Problem:
> For a file server, we want to have everything on sw RAID1.
> Having /home on a raid1 made from /dev/sda and /dev/sdb works fine.
> ?(Note that I used the whole devices not partitions.  So no
> "raid autodetect" partition type)
> 
> The machine in question also have /dev/hda and /dev/hdb on
> which I want to install linux on raid1, with several partitions.
> 
> The cumbersome way is to use partitions and create one md device for /, 
> one for /usr, one for /var, one for swap, and one for /usr/src.  
> I know this will work though.
> 
> The ideal way is to create a partitionable md device from /dev/hda+/dev/hdb,
> and then partition this md device into several components.
> 
> The problem with this, is that the initrd does not sufficiently recognize
> such a setup, so I can't have root on the partitioned md device.
> 
> While testing, I have been using a plain root on /dev/hda1, and a
> raid1 in degraded mode on /dev/hdb.  I have noticed that the
> initrd seems to detect the raid1 on hdb, but does not run mdadm
> in the way required to detect the partitions on the md device.
> 
> Therefore, I can't have root on /dev/md1p1 as I hope.
> 
> 
> The problem will probably not be solved in time for this server,
> which will use a more cumbersome setup lots of little md devices instead.
> 
> But I am interested in working with debian developers to improve this
> for the future.  I have a home machine where I can experiment with
> partitionable md device and even try booting from them. (That machine
> will have to use a amd64 kernel though.)
> 
> I could use some advice on changing an initrd - the simple and 
> hurried approach of unpacking the existing one with gzip+cpio, 
> adding an mdadm command and repacking with cpio+gzip didn't work.  

how about installing mdadm and then regenerating the initramfs with
update-initramfs -t -u

the md hooks from initramfs-tools are currently not in the mdadm
package so currently there is a race between the linux-image
installation, the later mdadm installation, which doesn't yet update
the initramfs.
 
> Anyway, a general solution for this problem probably shouldn't 
> hardcode an mdadm command either.  Ideally, the partitionable
> md device(s) should be detected and have the partitions recognized
> because they exist.  I am interested in looking at this,
> unless someone else already is busy doing it.  Is there
> some documentation on the proper way to change the initrd,
> so that the changes might get merged back for the benefit
> of others?
> 
> 
> Helge Hafting
> 
> -- System Information:
> Removed, for we don't run email on the server in question. Reportbug
> ran on a different machine. The server has kernel 2.6.15-1-686 
> from debian, and runs debian testing.  The risk of running 'testing'
> on this server is ok.
> 
> 
> -- 
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--
maks



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