grub on lvm2

grub on lvm2

[Mark Hannessen]

Hi list,

I have read on some websites that grub1.95 can boot from lvm
So I thought I'd give it a try.
I am quite new to grub2, so please forgive me my noobischness.
This is what i did:

1) I added /dev/hda to the physical extents ( pvcreate /dev/hda )
2) created a volume group on it ( vgcreate lvm2_core /dev/hda )
3) and created a boot partition on it ( lvcreate -L100M boot lvm2_core )
4) and wrote a partition on it: ( mkfs.reiserfs /dev/lvm2_core/boot )
5) mounted it on /boot and copied a bunch of grub .mod files to /boot/grub
6) created a config file called grub.cfg in /boot/grub/grub.cfg that 
looks like this:

# begin grub.cfg
set timeout=10
set default=0

menuentry "My Linux Kernel on (lvm2_core-boot)" {
    set root=(lvm2_core_boot)
    linux /boot/vmlinuz root=/dev/ram
    initrd /initrd

# end grub.cfg

so far so good (i hope..)
I now tried various combinations of grub-setup and grub-install but I 
can't seem to get it right...

could anyone give me a syntax that should work here?
or perhaps some documentation so I could figure it out myself..

thanks a lot!

Mark Hannessen

Re: grub on lvm2

[Hollis Blanchard]

On Sat, 2007-02-03 at 04:15 -0800, Mark Hannessen wrote:
> Hi list,
> 
> I have read on some websites that grub1.95 can boot from lvm
> So I thought I'd give it a try.
> I am quite new to grub2, so please forgive me my noobischness.
> This is what i did:
> 
> 1) I added /dev/hda to the physical extents ( pvcreate /dev/hda )
> 2) created a volume group on it ( vgcreate lvm2_core /dev/hda )
> 3) and created a boot partition on it ( lvcreate -L100M boot lvm2_core )
> 4) and wrote a partition on it: ( mkfs.reiserfs /dev/lvm2_core/boot )
> 5) mounted it on /boot and copied a bunch of grub .mod files to /boot/grub
> 6) created a config file called grub.cfg in /boot/grub/grub.cfg that 
> looks like this:
> 
> # begin grub.cfg
> set timeout=10
> set default=0
> 
> menuentry "My Linux Kernel on (lvm2_core-boot)" {
>     set root=(lvm2_core_boot)
>     linux /boot/vmlinuz root=/dev/ram
>     initrd /initrd
> 
> # end grub.cfg

I don't believe "set root" behaves properly. If that's the problem, you
will need to duplicate that value into both following lines.

> so far so good (i hope..)
> I now tried various combinations of grub-setup and grub-install but I 
> can't seem to get it right...

Perhaps you could be a little more specific.

> could anyone give me a syntax that should work here?
> or perhaps some documentation so I could figure it out myself..

All GRUB2 documentation is in the wiki: http://grub.enbug.org/

-Hollis

Re: grub on lvm2

[Michael Guntsche]

On Feb 7, 2007, at 2:00 PM, Mark Hannessen wrote:

>
> ok I now made it look like this:
>
> menuentry "My Linux Kernel on (lvm2_core-boot)" {
>     set root=(lvm2_core_boot)
>     linux (lvm2_core_boot)/boot/vmlinuz root=/dev/ram
>     initrd (lvm2_core_boot)/boot/initrd
> }
>

My config with lvm looks pretty similar but I am using an initramfs  
image and its looking like this

menuentry "Debian GNU/Linux, linux 2.6.20" {
   set root=(fatoftheland-main)
   linux /boot/vmlinuz-2.6.20 root=/dev/mapper/fatoftheland-main ro
   initrd  /boot/initrd.img-2.6.20
}


> this I used for my core.img
>
> grub-mkimage -d /boot/grub -v -o /boot/grub/core.img ls ext2 gpt pc  
> linux
> _linux boot chain configfile fshelp help lvm
>

As far as I remember (it has been a long time since I last created  
the core.img file) the order is important. Try

grub-mkimage -o /boot/grub/core.img pc lvm ext2 _chain

> and this is the most far I got:
>
> grub-setup -d /boot/grub -v -r '(lvm2_core-boot)' -m /boot/grub/ 
> device.map '(lvm2_core-boot)'
>

Use the real disk here and not the lvm VG.

grub-setup -r '(fatoftheland-main)' '(hd0)'.


This works for me.

Kind regards,
Michael

Re: grub on lvm2

[Mark Hannessen]

> > # begin grub.cfg
> > set timeout=10
> > set default=0
> >
> > menuentry "My Linux Kernel on (lvm2_core-boot)" {
> >     set root=(lvm2_core_boot)
> >     linux /boot/vmlinuz root=/dev/ram
> >     initrd /initrd
> >
> > # end grub.cfg
>
> I don't believe "set root" behaves properly. If that's the problem, you
> will need to duplicate that value into both following lines.

ok I now made it look like this: 

menuentry "My Linux Kernel on (lvm2_core-boot)" {
    set root=(lvm2_core_boot)
    linux (lvm2_core_boot)/boot/vmlinuz root=/dev/ram
    initrd (lvm2_core_boot)/boot/initrd
}

> > I now tried various combinations of grub-setup and grub-install but I
> > can't seem to get it right...
>
> Perhaps you could be a little more specific.

this I used for my core.img

grub-mkimage -d /boot/grub -v -o /boot/grub/core.img ls ext2 gpt pc linux 
_linux boot chain configfile fshelp help lvm

and this is the most far I got:

grub-setup -d /boot/grub -v -r '(lvm2_core-boot)' -m /boot/grub/device.map '(lvm2_core-boot)'

grub-setup: info: prefix = /grub
grub-setup: info: getting the size of /boot/grub/boot.img
grub-setup: info: reading /boot/grub/boot.img
grub-setup: info: getting the size of /boot/grub/boot.img
grub-setup: info: getting the size of /boot/grub/core.img
grub-setup: info: reading /boot/grub/core.img
grub-setup: info: getting the size of /boot/grub/core.img
grub-setup: error: unknown device

why I grub probe I get the same:

grub-probe -v /boot/grub
grub-probe: info: changing current directory to /dev
grub-probe: info: changing current directory to i2c
grub-probe: info: changing current directory to lvm2_server1
grub-probe: info: changing current directory to lvm2_core
grub-probe: info: changing current directory to shm
grub-probe: info: changing current directory to pts
grub-probe: info: changing current directory to bus
grub-probe: info: changing current directory to usb
grub-probe: info: changing current directory to 004
grub-probe: info: changing current directory to 003
grub-probe: info: changing current directory to 002
grub-probe: info: changing current directory to 001
grub-probe: info: changing current directory to snd
grub-probe: info: changing current directory to sound
grub-probe: info: changing current directory to net
grub-probe: info: changing current directory to misc
grub-probe: info: changing current directory to pktcdvd
grub-probe: info: changing current directory to xen
grub-probe: info: changing current directory to mapper
cannot find a GRUB drive for lvm2_core-boot.

Mark