[linux-lvm] Boot Mgr support for '/boot' on LVM2 volumes ?

[linux-lvm] Boot Mgr support for '/boot' on LVM2 volumes ?

[John Smith]

Hi.


I was wondering if booting from an LVM2 volume group is supposed to be
supported with lilo (preferred) or GRUB. For example, is it supported
to use a '/boot' device, when that is a LVM2 volume residing in an
LVM2 volume group ?

Last time I checked, having /boot on a LVM2 device using lilo was
still considered 'unsupported', or at least considered to be "not a
very good idea". If I recall correctly, this had something to do with
the fact that "/boot" had to be located on a linear, contiguous volume
for bootloaders like lilo and grub to be able to read it.  And that
with something like LVM, it's on very easy for a volume to be
non-contiguous.

Is this still the case with the current release of LVM2, or has this
been worked-around in current releases ?


Sincerely,


John Smith.

Re: [linux-lvm] Boot Mgr support for '/boot' on LVM2 volumes ?

[Luca Berra]

On Sun, Mar 05, 2006 at 05:46:45PM +0100, John Smith wrote:
>still considered 'unsupported', or at least considered to be "not a
Christophe Saout made some patches to lilo to be able to boot from a
lvm2 /boot (http://www.saout.de/misc/), this patch has been adopted into
major distributions.
>very good idea". If I recall correctly, this had something to do with
>the fact that "/boot" had to be located on a linear, contiguous volume
>for bootloaders like lilo and grub to be able to read it.  And that
this is correct, the lv for /boot is to be linear and contiguus, it is
user responsability to ensure this.

L.

-- 
Luca Berra -- bluca@comedia.it
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Re: [linux-lvm] Boot Mgr support for '/boot' on LVM2 volumes ?

[John Smith]

On 3/7/06, Luca Berra <bluca@comedia.it> wrote:
>
> Christophe Saout made some patches to lilo to be able to boot from a
> lvm2 /boot (http://www.saout.de/misc/), this patch has been adopted into
> major distributions.
>
Cool, I didnt know that.

>
> this is correct, the lv for /boot is to be linear and contiguus, it is
> user responsability to ensure this.
>
UUhhmm...Ok, now im confused. If 'the user' still has to make sure
that /boot is linear and contiguous, then :
1.) Exactly, what, does the patch *do* then ?
2.) How does 'the user' (me, in this case) ensure this ?


Sincerely,

John Smith.

Re: [linux-lvm] Boot Mgr support for '/boot' on LVM2 volumes ?

[Luca Berra]

On Tue, Mar 07, 2006 at 10:21:49PM +0100, John Smith wrote:
>On 3/7/06, Luca Berra <bluca@comedia.it> wrote:
>>
>> Christophe Saout made some patches to lilo to be able to boot from a
>> lvm2 /boot (http://www.saout.de/misc/), this patch has been adopted into
>> major distributions.
>>
>Cool, I didnt know that.
>
>>
>> this is correct, the lv for /boot is to be linear and contiguus, it is
>> user responsability to ensure this.
>>
>UUhhmm...Ok, now im confused. If 'the user' still has to make sure
>that /boot is linear and contiguous, then :
>1.) Exactly, what, does the patch *do* then ?
it allows lilo to query device mapper and map a dm device to physical
sectors on the disk.
>2.) How does 'the user' (me, in this case) ensure this ?
>
make /boot a separate logical volume than /
do not extend it.

L.

-- 
Luca Berra -- bluca@comedia.it
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[linux-lvm] Re: Boot Mgr support for '/boot' on LVM2 volumes ?

[Claus Färber]

Luca Berra schrieb:
> this is correct, the lv for /boot is to be linear and contiguus, it is
> user responsability to ensure this.

What about adding a "boot" flag to LVs? It set, it could have the 
following effect:

. Tools will ensure that the LV remains linear and contiguus and at the 
beginning of a PV.
. (Later) the LV is mirrored into every PV marked "bootable".

With these features, an OS could be booted from any disk. With mirroring 
(RAID-on-LVM) you could boot a system even if your primary disk fails.

Claus

Re: [linux-lvm] Re: Boot Mgr support for '/boot' on LVM2 volumes ?

[Alasdair G Kergon]

On Sat, Mar 25, 2006 at 06:31:41PM +0100, Claus F�rber wrote:
> What about adding a "boot" flag to LVs? It set, it could have the 
> following effect:
 
Well we already have --alloc contiguous which comes close.

This would be a subset: contiguous and not striped etc., but could
be mirrored to similarly-contiguous space.

--alloc bootable perhaps.

Alasdair
-- 
agk@redhat.com