[linux-lvm] LVM, lilo and MBR?

[linux-lvm] LVM, lilo and MBR?

[Urs Thuermann]

I think this was asked on this list before but I couldn't find it
anymore.

I would like to make my 3 SCSI harddisk drives into PVs without
partitioning them, i.e.

    pvcreate /dev/sda; pvcreate /dev/sdb; pvcreate /dev/sdc

But I need the MBR on /dev/sda to boot the system and I want to use
lilo.  Thus, I have 2 questions:

1. Is the first sector of a PV volume use by LVM or can I pvcreate
   /dev/sda and still use the MBR of /dev/sda to boot the system?
   Where does the VGDA start and how large is it?

2. IIRC, someone had a patch for lilo to load the kernel and initrd
   image from a LV.  Where can I get it?  And will it go into the
   standard lilo package?

These questions should probably go into the FAQ.


urs

Re: [linux-lvm] LVM, lilo and MBR?

[Patrick Caulfield]

On Tue, Mar 27, 2001 at 11:34:08AM +0200, Urs Thuermann wrote:
> 
> 1. Is the first sector of a PV volume use by LVM or can I pvcreate
>    /dev/sda and still use the MBR of /dev/sda to boot the system?
>    Where does the VGDA start and how large is it?

Yes it is. Don't run LILO on /dev/sda if it's a PV because it will destroy it.
You should partition the disk into /dev/sda1 (that way the PV will start further
in and leave space for LILO)
 
> 2. IIRC, someone had a patch for lilo to load the kernel and initrd
>    image from a LV.  Where can I get it?  And will it go into the
>    standard lilo package?

Andreas will be along in a moment !

patrick

Re: [linux-lvm] LVM, lilo and MBR?

[Urs Thuermann]

Patrick Caulfield <caulfield@sistina.com> writes:

> Yes it is. Don't run LILO on /dev/sda if it's a PV because it will
> destroy it.  You should partition the disk into /dev/sda1 (that way
> the PV will start further in and leave space for LILO)

Hm, I hoped I could get rid of the broken partitioning scheme of the
PC and C/H/S addressing used in the partition table.

Are there objections to change LVM so that the VGDA is placed at some
fixed offset (say 1 sector or 1 block (1K)) from the beginning of the
PV?  This is how many file systems also use block devices to avoid
conflicts with MBR, boot sectors and so on.

BTW, are the other partitioning schemes that I could use than the one
that the standard MBR and MSDOS use?  Can the linux kernel recognize
other partition tables which only use absolut, linear sector numbers?


urs

Re: [linux-lvm] LVM, lilo and MBR?

[Patrick Caulfield]

On Tue, Mar 27, 2001 at 03:43:07PM +0200, Urs Thuermann wrote:
> Patrick Caulfield <caulfield@sistina.com> writes:
> 
> > Yes it is. Don't run LILO on /dev/sda if it's a PV because it will
> > destroy it.  You should partition the disk into /dev/sda1 (that way
> > the PV will start further in and leave space for LILO)
> 
> Hm, I hoped I could get rid of the broken partitioning scheme of the
> PC and C/H/S addressing used in the partition table.
> 
> Are there objections to change LVM so that the VGDA is placed at some
> fixed offset (say 1 sector or 1 block (1K)) from the beginning of the
> PV?  This is how many file systems also use block devices to avoid
> conflicts with MBR, boot sectors and so on.

There are no plans to do this for the near future

 
> BTW, are the other partitioning schemes that I could use than the one
> that the standard MBR and MSDOS use?  Can the linux kernel recognize
> other partition tables which only use absolut, linear sector numbers?

LVM works quite happily with any of Linux's supported disk labelling systems,
but I think Sun and IRIX disk labels still use cylinders.

If you're really worried about broken partitioning systems then perhaps you
should use a less broken platform than a PC :-) Alphas are very nice, and you
could use the BSD disklabel utility to slice up the disk.


patrick

Re: [linux-lvm] LVM, lilo and MBR?

[Andreas Dilger]

Urs Thuermann wrote:
> Patrick Caulfield <caulfield@sistina.com> writes:
> > 2. IIRC, someone had a patch for lilo to load the kernel and initrd
> >    image from a LV.  Where can I get it?  And will it go into the
> >    standard lilo package?
> 
> Andreas will be along in a moment !

Yes, patch for LILO has already been sent to LVM mailing lists a
couple of times.  I found a copy at:

http://marc.theaimsgroup.com/?l=linux-lvm&m=98451699131728&w=4

I have not yet submitted it to the LILO maintainer, because if you try
to run it on older LVM kernel code (i.e. what's in the official 2.4.2
kernel), it will immediately crash your system.  The Sistina folks have
told me they will submit an LVM kernel patch with the fix...

> > Don't run LILO on /dev/sda if it's a PV because it will destroy
> > it.  You should partition the disk into /dev/sda1 (that way
> > the PV will start further in and leave space for LILO)
> 
> Hm, I hoped I could get rid of the broken partitioning scheme of the
> PC and C/H/S addressing used in the partition table.

But then again, your MBR has the same problems, so why worry?  Even so,
you only need the partition table on the boot disk, so no big deal.

> Are there objections to change LVM so that the VGDA is placed at some
> fixed offset (say 1 sector or 1 block (1K)) from the beginning of the
> PV?  This is how many file systems also use block devices to avoid
> conflicts with MBR, boot sectors and so on.

Yes, because it will break every LVM setup around.  Too bad it wasn't
in the original design, but it is too late to change.

Cgeers, Andreas
-- 
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

Re: [linux-lvm] LVM, lilo and MBR?

[Heinz Mauelshagen]

On Tue, Mar 27, 2001 at 11:11:28AM -0700, Andreas Dilger wrote:
> Urs Thuermann wrote:
> > Patrick Caulfield <caulfield@sistina.com> writes:
> > > 2. IIRC, someone had a patch for lilo to load the kernel and initrd
> > >    image from a LV.  Where can I get it?  And will it go into the
> > >    standard lilo package?
> > 
> > Andreas will be along in a moment !
> 
> Yes, patch for LILO has already been sent to LVM mailing lists a
> couple of times.  I found a copy at:
> 
> http://marc.theaimsgroup.com/?l=linux-lvm&m=98451699131728&w=4
> 
> I have not yet submitted it to the LILO maintainer, because if you try
> to run it on older LVM kernel code (i.e. what's in the official 2.4.2
> kernel), it will immediately crash your system.  The Sistina folks have
> told me they will submit an LVM kernel patch with the fix...
> 

Which is already history now.
Linus has it since 10 days or something...

Regards,
Heinz      -- The LVM guy --


> > > Don't run LILO on /dev/sda if it's a PV because it will destroy
> > > it.  You should partition the disk into /dev/sda1 (that way
> > > the PV will start further in and leave space for LILO)
> > 
> > Hm, I hoped I could get rid of the broken partitioning scheme of the
> > PC and C/H/S addressing used in the partition table.
> 
> But then again, your MBR has the same problems, so why worry?  Even so,
> you only need the partition table on the boot disk, so no big deal.
> 
> > Are there objections to change LVM so that the VGDA is placed at some
> > fixed offset (say 1 sector or 1 block (1K)) from the beginning of the
> > PV?  This is how many file systems also use block devices to avoid
> > conflicts with MBR, boot sectors and so on.
> 
> Yes, because it will break every LVM setup around.  Too bad it wasn't
> in the original design, but it is too late to change.
> 
> Cgeers, Andreas
> -- 
> Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
>                  \  would they cancel out, leaving him still hungry?"
> http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm

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