Bug#61065: Adam Di Carlo: Re: Bug#61065: Need /dev/md0 for boot/install RAID support in root.bin
Mike Bilow <mikebw@colossus.bilow.com> writes:
> I'm not sure what the mail problem is. If it is something on our end, let
> me know and I'll look into it as I serve as postmaster here.
No, it was on my end.
> > Note that the standard, "vanilla" kernel has changed in the following way:
[...]
> > Is this enough? I guess not... it doesn't have md support?
>
> I will have to check into this. The start of the problem is that there is
> no proper software RAID support in the kernel source tree. The software
> RAID support which is present is years old and is referenced as v0.4x
> RAID. The newer code, which completely replaces the earlier code and is
> currently being distributed as kernel source patches by Ingo Molnar (at
> http://people.redhat.com/mingo) which is referenced as v0.90 RAID.
Ok -- you're asking for kernel patching. This is not for us to
decide. This is for the kernel-source maintainer (Herbert Xu) to
decide. I would assume it's too late in the freeze process to change
this in potato. I've CC'd him.
[...]
> > > drop to fdisk manually to set partition types to
> > > 0xFD (RAID autodetect),
> >
> > Can't cfdisk set this partition type? If not, please file a bug
> > against cfdisk.
>
> There is no problem with fdisk/cfdisk as far as know. (I used fdisk and
> did not test cfdisk.) The issue is that the Debian install program does
> not seem to understand how to make any use of /dev/md? devices even after
> they exist, so what I meant by "manually" is that I had to drop out to a
> shell to run fdisk, mkraid, mke2fs, and mount before I could continue the
> regular install. Whether this is appropriate behavior for the
> installation program is a matter of opinion, and at worst is a wishlist
> bug. One could argue that, if one is installing onto RAID for the boot
> volume, then one ought to know what one is doing with a shell prompt.
> On the other hand, there is also no good reason that the install program
> should not be able to handle this, at least all but mkraid.
I thought if you are *booting* into a RAID system, you really really
need a initrd/linuxrc system. Since we don't support this in the
boot-floppies, doesn't that mean by definition we don't support
booting on a RAID fs?
> > > run mkraid (from a mounted floppy) to unite the partitions,
> >
> > mkraid isn't part of root.bin, is it? I think we have room on i386 at
> > least to add it, btw.
>
> Well, raidstart would be nice, too, especially if the rescue disk is
> really expected to be able to serve as a "rescue" disk. Most of the other
> RAID components in raidtool2 are actually just symlinks to either mkraid
> or raidstart, anyway, so they consume essentially no space in root.bin.
Well, see the above question.
> I am not sure if /dev/md? devices are created in the base file system. I
> suspect they are not, and that this is currently the responsibility of the
> raidtools2 package rather than the base installation. This would be
> consistent with Debian Policy, I think, except that it is now possible to
> boot on software RAID and therefore the responsibility should be moved.
>
> As long as the /proc filesystem is in the kernel, you can do an existence
> check for /proc/mdstat. If it exists, then the kernel has RAID support
> and the /dev/md? devices should probably be created during base install.
So long as raidtools2 currently handles it and everything works, I'm
perfectly happy to let it stay that way. We're trying to release very
soon and we simply cannot embark on coordinated changes like this at
this phase.
> > > In general, support for installing to bootable software RAID should
> > > probably be added to boot-floppies at some point for the 2.4 kernel.
> >
> > There are limitations on what we can add to the kernel. But I think
> > this is in the cards for woody.
>
> Once software RAID is in the mainstream 2.4 kernel, combined with the fact
> that it was added to mainstream Lilo last week, this is going to be an
> expected part of a Linux distribution and we absolutely must provide it.
> The fact that I was actually able to do it successfully with potato by
> replacing the kernel and Lilo is an indication that we are very close.
Yes, I understand. I'm happy to do whatever is pretty easy to do
(such as creating the md devices in root.bin). I don't think RAID
will be fully supported in potato, however -- too many changes are
required and we are too far into the freeze.
--
.....Adam Di Carlo....adam@onShore.com.....<URL:http://www.onShore.com/>
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