Hi,

I installed Debian on top of LVM and software RAID1 following this:

http://dev.jerryweb.org/raid/


Everything is fine except that I cannot boot the Debian afterwards
("Insert boot disk" message from the bios). I used /dev/sdc and
/dev/sdd. First problem is that I do not know which hdd I should enter
as the first boot device in the bios. Moreover, obviously the bios does
not see the /dev/md0 array, since I guess first the raid array should be
started in order for grub to be loaded. I explicitly issued grub-install
/dev/md0 using the recovery mode of the debian installer, but that did
not help.

Thanks in advance,
Ivan


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Ivan Glushkov wrote:
> Hi,
>
> I installed Debian on top of LVM and software RAID1 following this:
>
> http://dev.jerryweb.org/raid/
>
>
> Everything is fine except that I cannot boot the Debian afterwards
> ("Insert boot disk" message from the bios). I used /dev/sdc and
> /dev/sdd. First problem is that I do not know which hdd I should enter
> as the first boot device in the bios. Moreover, obviously the bios does
> not see the /dev/md0 array, since I guess first the raid array should be
> started in order for grub to be loaded. I explicitly issued grub-install
> /dev/md0 using the recovery mode of the debian installer, but that did
> not help.
>
> Thanks in advance,
> Ivan
>
>
>
Ivan,

you can not put grub (/boot) on an LVM. You can put /boot on a raid1.
If you made one raid1 device and made one partition on md0 you will not
be able to boot (assuming you then put LVM on top of that one
partition/used all of md0).

Redo what you did only make either two partitions to md0, one for boot
(110Mb is large enough for most) and on partition2 put the rest of your
system ontop of the LVM. Or, partition your two hds to have two mdadm
raid1 . One small md0 for /boot and one md1 for the system with LVM on it.

You will then have to install grub on to hdd or if hdc fails, you will
not be able to boot as grub will be installed onto hdc MBR. Makes sense?

HTH

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Ivan,

My response probable did not make any sense. I went and dug up a blog
entry I made and reposted it. I covers the subject of how to make a
/boot on a software raid one. It does not cover the install, but rather
how to convert to a raid1 once you are up and running and how to install
grub onto both (or all) members of the array. www.damtek.com

HTH

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Damon L. Chesser wrote:
> Ivan Glushkov wrote:
>> Hi,
>>
>> I installed Debian on top of LVM and software RAID1 following this:
>>
>> http://dev.jerryweb.org/raid/
>>
>>
>> Everything is fine except that I cannot boot the Debian afterwards
>> ("Insert boot disk" message from the bios). I used /dev/sdc and
>> /dev/sdd. First problem is that I do not know which hdd I should enter
>> as the first boot device in the bios. Moreover, obviously the bios does
>> not see the /dev/md0 array, since I guess first the raid array should be
>> started in order for grub to be loaded. I explicitly issued grub-install
>> /dev/md0 using the recovery mode of the debian installer, but that did
>> not help.
>>
>> Thanks in advance,
>> Ivan
>>
>>
>>
> Ivan,
>
> you can not put grub (/boot) on an LVM. You can put /boot on a raid1.
> If you made one raid1 device and made one partition on md0 you will not
> be able to boot (assuming you then put LVM on top of that one
> partition/used all of md0).

No, that's not the problem. I followed exactly the mentioned article.
There, two disks are used and partitioned in two partitions - the first
ones are used for one RAID1, which is formatted as ext3 and used for the
/boot directory (i.e. no lvm for /boot). The second partitions on both
disks are arranged in a second RAID1 array on which I have created
separate logical volumes for / /usr /var and so on.

>
> Redo what you did only make either two partitions to md0, one for boot
> (110Mb is large enough for most) and on partition2 put the rest of your
> system ontop of the LVM. Or, partition your two hds to have two mdadm
> raid1 . One small md0 for /boot and one md1 for the system with LVM on it.
>
> You will then have to install grub on to hdd or if hdc fails, you will
> not be able to boot as grub will be installed onto hdc MBR. Makes sense?

I taught I have to install the grub on the raid array, thus the grub
will put a copy of itself on the first partition on both hard drives,
used for the raid1, right?


>
> HTH
>




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snip
>
> I taught I have to install the grub on the raid array, thus the grub
> will put a copy of itself on the first partition on both hard drives,
> used for the raid1, right?
>

Wrong AFAIK. You can do that IF you have a boot loader on the MBR
pointing to grub. BIOS does not read software raid and knows nothing
about software raid. Software raid does not come into play until the
kernel via initrd is loaded. Install to the MBR of the first HD of the
array, then use grub to install into the MBR of the other members. If I
am wrong, then it is news to me, but hey, I will learn new things! See
my old "howto" on Linux, grub and raid at damtek.com for the exact
commands. It is not pretty, but it will work.

HTH

--
Damon L. Chesser
damon@damtek.com
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Damon L. Chesser wrote:
> snip
>>
>> I taught I have to install the grub on the raid array, thus the grub
>> will put a copy of itself on the first partition on both hard drives,
>> used for the raid1, right?
>>
>
> Wrong AFAIK. You can do that IF you have a boot loader on the MBR
> pointing to grub.

Now I am confused. Isn't grub a boot loader? Why would I need another
boot loader pointing to grub? I want to put grub on the MBR of both hard
drives from which my raid1 array consist of.

BIOS does not read software raid and knows nothing
> about software raid.

Indeed, but I do not expect from the bios to read my raid array. I
merely want it to look for boot record in the MBR of one of the two hard
drives on which I have my raid arrays.

Software raid does not come into play until the
> kernel via initrd is loaded. Install to the MBR of the first HD of the
> array, then use grub to install into the MBR of the other members.

What I meant with the paragraph you are referring to is exactly that:
issuing:

grub-install /dev/md0

should install (as fas as I understand it) a copy of grub in each hdd
from which the raid1 consist of (note: the partitions from both hard
drives included in md0 are both 512 MB and starting from the beginning
of the hard drives).

If I
> am wrong, then it is news to me, but hey, I will learn new things! See
> my old "howto" on Linux, grub and raid at damtek.com for the exact
> commands. It is not pretty, but it will work.

I tried that. Thanks.

Basically the problem was easily solved. I had to tag both partitions to
be used for my /boot raid1 array as primary and bootable (stupid of me,
I know). But there is now another problem:

I see already the grub initial screen, but when I hit enter, I get the
following:

Booting 'Debian GNU/Linux, kernel 2.6.24-1-amd64'

root (hd5,0)
Filesystem type unknown, partition type 0x7
kernel //vmlinuz-2.6.24-1-amd64 root=/dev/mapper/vg00-root ro linux26 quiet

Error 17: Cannot mount selected partition

Press any key to continue...

I suppose grub does not know anything about LVM and the partitions on
that. If I am right, I have to rebuild initrd, right? But how do I tell
it to enable the lvm?

Cheers,
Ivan


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Ivan Glushkov wrote:
> Damon L. Chesser wrote:
>
>> snip
>>
>>> I taught I have to install the grub on the raid array, thus the grub
>>> will put a copy of itself on the first partition on both hard drives,
>>> used for the raid1, right?
>>>
>>>
>> Wrong AFAIK. You can do that IF you have a boot loader on the MBR
>> pointing to grub.
>>
>
> Now I am confused. Isn't grub a boot loader? Why would I need another
> boot loader pointing to grub? I want to put grub on the MBR of both hard
> drives from which my raid1 array consist of.
>
> BIOS does not read software raid and knows nothing
>
>> about software raid.
>>
>
> Indeed, but I do not expect from the bios to read my raid array. I
> merely want it to look for boot record in the MBR of one of the two hard
> drives on which I have my raid arrays.
>
> Software raid does not come into play until the
>
>> kernel via initrd is loaded. Install to the MBR of the first HD of the
>> array, then use grub to install into the MBR of the other members.
>>
>
> What I meant with the paragraph you are referring to is exactly that:
> issuing:
>
> grub-install /dev/md0
>
> should install (as fas as I understand it) a copy of grub in each hdd
> from which the raid1 consist of (note: the partitions from both hard
> drives included in md0 are both 512 MB and starting from the beginning
> of the hard drives).
>

Truly, I don't know if you install grub onto a raid1 if it will install
it onto the MBR of both physical HDs. I just always made partitions for
the /boot, installed to one, moved the data around and made a mdX out of
it and installed grub onto the other member. Re-inventing the wheel?
Probably.
> If I
>
>> am wrong, then it is news to me, but hey, I will learn new things! See
>> my old "howto" on Linux, grub and raid at damtek.com for the exact
>> commands. It is not pretty, but it will work.
>>
>
> I tried that. Thanks.
>
> Basically the problem was easily solved. I had to tag both partitions to
> be used for my /boot raid1 array as primary and bootable (stupid of me,
> I know). But there is now another problem:
>
> I see already the grub initial screen, but when I hit enter, I get the
> following:
>
> Booting 'Debian GNU/Linux, kernel 2.6.24-1-amd64'
>
> root (hd5,0)
> Filesystem type unknown, partition type 0x7
> kernel //vmlinuz-2.6.24-1-amd64 root=/dev/mapper/vg00-root ro linux26 quiet
>
> Error 17: Cannot mount selected partition
>
> Press any key to continue...
>
> I suppose grub does not know anything about LVM and the partitions on
> that. If I am right, I have to rebuild initrd, right? But how do I tell
> it to enable the lvm?
>

You have me there, it should have done it automagicaly when it
installed. Use rescue mode, but I am not sure what command you should
use to re-generate it. Perhaps chroot to your /, then try to run mkinitrd.

do you have a line in grub like this?

title Debian GNU/Linux, kernel 2.6.25-1-amd64
root (hd0,5)
kernel /boot/vmlinuz-2.6.25-1-amd64 root=/dev/hda6 ro quiet
------->>>>>>> initrd /boot/initrd.img-2.6.25-1-amd64
<<<<<<<<<<<-------

If not, that would seem to mean you don't have an intrd.


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http://www.linkedin.com/in/dchesser


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Ivan Glushkov wrote:
> Damon L. Chesser wrote:
>
>> snip
>>
>>> I taught I have to install the grub on the raid array, thus the grub
>>> will put a copy of itself on the first partition on both hard drives,
>>> used for the raid1, right?
>>>
>>>
>> Wrong AFAIK. You can do that IF you have a boot loader on the MBR
>> pointing to grub.
>>
>
> Now I am confused. Isn't grub a boot loader? Why would I need another
> boot loader pointing to grub? I want to put grub on the MBR of both hard
> drives from which my raid1 array consist of.
>
You could use Windows boot loader to point to grub, for example. It
would give you a menu in Windows boot to pick Windows or Debian. Have
not done that in years.

> grub-install /dev/md0
> should install (as fas as I understand it) a copy of grub in each hdd
> from which the raid1 consist of (note: the partitions from both hard
> drives included in md0 are both 512 MB and starting from the beginning
> of the hard drives).
>
Ivan,

I looked quickly on google and so far articles I see refer to installing
grub onto the 2nd HD using the grub command. I will go back and look at
the howto you posted and see if they say anything different. I am NOT
the raid/grub master and sure not the final word on the subject.
>
>
> Cheers,
> Ivan
>
>
>

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> I looked quickly on google and so far articles I see refer to
> installing grub onto the 2nd HD using the grub command. I will go
> back and look at the howto you posted and see if they say anything
> different. I am NOT the raid/grub master and sure not the final word
> on the subject.
From http://dev.jerryweb.org/raid/ :

> You may now continue by first installing GRUB on the boot sector and
> proceed with the complete installation of Debian which will be written
> symmetrically on the two disks in RAID.
>
> Enjoy Debian with the RAID set up for both boot and data such that
> even if one disk crashes you will be able to restore your
> configuration (do not forget to give to your new disk partitions
> identical to the old disk and to copy GRUB to the boot partition if
> necessary).
>

This seems to be saying install GRUB onto the MBR of a disk (md devices
don't have an MBR) and note that part where it says to copy GRUB to the
boot partition. I don't know exactly what he meant by that since the
only way I know to copy GRUB is to run the grub command and install it
onto a MBR. By definition, a raid1 that is restored will copy all it's
data to the replaced HD, leaving no reason to "copy GRUB to the boot
partition" unless he is meaning the grub command.

If anybody knows different, please educate me.


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On Wed, May 07, 2008 at 02:48:57PM -0400, Damon L. Chesser wrote:
> Truly, I don't know if you install grub onto a raid1 if it will install
> it onto the MBR of both physical HDs.

I have not done this recently, but I am sure that some yeras ago it was
not so. I had to install separately grub on the MBR of both disks (say,
sda and sdb, or hd0 and hd1 in grub language). And since then I have not
changed method. Moreover with

Linkname: grub raid1 mdadm - Google Search
URL:
http://www.google.com/search?num=100...dm&btnG=Search

I do not see in the first hits really different methods.

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