Re: LVM and devfs (I'm intrigued)
On Mon, Mar 08, 2004 at 07:25:02PM +1000, Andrew Pollock wrote:
> Hi Patrick,
>
> I've just read #123069, and this is after I yesterday briefly had LVM up and
> running on a stock Debian kernel without devfs mount or devfsd installed.
>
> I shortly afterwards hosed the install and now have LVM on top of a RAID1
> device (again, without devfs involved, but with a stock kernel).
>
> For the brief period of time that I had the straight LVM going, the sky
> didn't fall on me.
>
> What is the exact nature of the issues with LVM1 and kernels with devfs
> enabled (but not mounted)? Does it just randomly screw up, or is it not
> supposed to work at all?
>
> I'm doing a bit of testing work for the new debian-installer, and I recently
> provided a patch for the lvmcfg udeb (it previously wasn't installing lvm10
> in the new installation if the installer had set up logical volumes).
>
> Currently, on a newly installed Debian system installed by d-i, where LVM
> has been employed, does not have devfsd installed, and it's using a stock
> Debian kernel, so devfs is enabled, but not mounted. If this is some sort of
> random time bomb, we need to address it and ensure that devfsd does get
> installed, and devfs does get mounted, because the last thing we want to do
> is have d-i spitting out unreliable sarge installs that use LVM.
That's interesting.
It was always the case that if you have devfs in the kernel but not mounted, the
partition names in /proc/partitions showed devfs names rather than "normal"
/dev/sda* type names. LVM can't reconcile those names at all so it will refuse
to create VGs, saying it can't find the devices.
I must confess I haven't tried this for some time, I know for sure that the
LVM code that deals with this hasn't changed. (very little of LVM1 has changed
for ages now and it's going to stay that way). But then, it also seems
very unlikely that devfs has changed here either. I'll have a look at it some
time and see if I can find out what's happening because it certainly didn't work
(I remember a flurry of bug reports about it!)
So, it's not a random time-bomb. If it works then it won't cause any corruption
or later problems
--
patrick
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