SEO

My system has three IDE/ATA drives, hda is a hard disk, hdc is a
dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
disks which are sda and sdb. What order would they show up in to grub?
(ie: hd0, hd1, hd2 ?)

On Sun, 18 Feb 2007 10:22:19 -0500, ken scharf wrote:

> My system has three IDE/ATA drives, hda is a hard disk, hdc is a
> dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
> disks which are sda and sdb. What order would they show up in to grub?
> (ie: hd0, hd1, hd2 ?)

It's hard to say - it might be hd0 hd4 hd5 - how about doing a simple
install to each one. Then run grub and have it search for
/boot/grub/stage1?

ken scharf wrote:
> My system has three IDE/ATA drives, hda is a hard disk, hdc is a
> dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
> disks which are sda and sdb. What order would they show up in to grub?
> (ie: hd0, hd1, hd2 ?)

That depends on your grubs device.map, as it's there the grub devices are
translated to udev/devfs-devices.

--

//Aho

J.O. Aho wrote:
> ken scharf wrote:
>> My system has three IDE/ATA drives, hda is a hard disk, hdc is a
>> dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
>> disks which are sda and sdb. What order would they show up in to grub?
>> (ie: hd0, hd1, hd2 ?)
>
> That depends on your grubs device.map, as it's there the grub devices
> are translated to udev/devfs-devices.
>
Yes, I see the file and the translation is there.
When is the device.map file created, and can I edit it to change things?
If I boot off my sata drives I'd want /dev/sda to be hd0
If I boot off my ide drive I'd want /dev/hda to be hd0.

But in my case /dev/sda and /dev/sdb will be part of a raid1 array.
So grub won't use /dev/sdb unless /dev/sda fails and I point my bios to
boot /dev/sdb (which now becomes sda!) I'd have to install grub onto
both disks but the device mapping might be different?

I don't think grub knows about raid and boots off the raw disk, the raid
array being established AFTER the kernel loads off the raw disk.
Correct?

ken scharf <wa2mzeNOSPAMBOTS@bellsouth.net> writes:

> I don't think grub knows about raid and boots off the raw disk, the raid
> array being established AFTER the kernel loads off the raw disk.
> Correct?

In all of the systems using RAID which I have seen, the RAID
controller initialises before Grub and both Grub and the kernel see
the whole array as a single device.

ken scharf wrote:
> J.O. Aho wrote:
>> ken scharf wrote:
>>> My system has three IDE/ATA drives, hda is a hard disk, hdc is a
>>> dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
>>> disks which are sda and sdb. What order would they show up in to grub?
>>> (ie: hd0, hd1, hd2 ?)
>> That depends on your grubs device.map, as it's there the grub devices
>> are translated to udev/devfs-devices.
>>
> Yes, I see the file and the translation is there.
> When is the device.map file created

Think this is created during install of Grub, there are also options to use
with the grub-install command that would recreate it.

> and can I edit it to change things?
> If I boot off my sata drives I'd want /dev/sda to be hd0
> If I boot off my ide drive I'd want /dev/hda to be hd0.

Yes, you can edit it, but you either name the SATA drive as hd0 or the IDE,
you don't edit that between boots, you have the grub.conf where you tell what
to boot from where and you can "rename" the hard drives there too, this is
needed if you have microsoft on a secondary hard drive (microsoft is a bit
stupid and wants only boot from hd0).


> But in my case /dev/sda and /dev/sdb will be part of a raid1 array.
> So grub won't use /dev/sdb unless /dev/sda fails and I point my bios to
> boot /dev/sdb (which now becomes sda!) I'd have to install grub onto
> both disks but the device mapping might be different?

If you only have the root filesystem on the SATA raid, then you don't have to
name the harddrives for grub, as at that point it's the kernel who has taken
over things.


> I don't think grub knows about raid and boots off the raw disk, the raid
> array being established AFTER the kernel loads off the raw disk.

Easiest is always to have /boot on it's own slice which is a standard non
raided filesystem. I'm really not that sure about the raid, I never use it
myself, but in theory grub could be able to read the hardware raided device,
but not softraided, than you need the kernel for.

--

//Aho

So anyway, it was like, 19:29 CET Feb 18 2007, you know? Oh, and, yeah,
Graham Murray was all like, "Dude,
> ken scharf <wa2mzeNOSPAMBOTS@bellsouth.net> writes:

>> I don't think grub knows about raid and boots off the raw disk, the
>> raid array being established AFTER the kernel loads off the raw
>> disk. Correct?
>
> In all of the systems using RAID which I have seen, the RAID
> controller initialises before Grub and both Grub and the kernel see
> the whole array as a single device.

There's software raid too.

--
Time flies like an arrow, fruit flies like a banana. Perth ---> *
11:50:01 up 102 days, 9:31, 5 users, load average: 0.28, 0.23, 0.15
Linux 2.6.18.1 x86_64 GNU/Linux Registered Linux user #261729

J.O. Aho wrote:
> ken scharf wrote:
>> J.O. Aho wrote:
>>> ken scharf wrote:
>>>> My system has three IDE/ATA drives, hda is a hard disk, hdc is a
>>>> dvd+/-RW drive and hdd is a dvd-ram drive. I also have two sata hard
>>>> disks which are sda and sdb. What order would they show up in to grub?
>>>> (ie: hd0, hd1, hd2 ?)
>>> That depends on your grubs device.map, as it's there the grub devices
>>> are translated to udev/devfs-devices.
>>>
>> Yes, I see the file and the translation is there.
>> When is the device.map file created
>
> Think this is created during install of Grub, there are also options to
> use with the grub-install command that would recreate it.
>
>> and can I edit it to change things?
>> If I boot off my sata drives I'd want /dev/sda to be hd0
>> If I boot off my ide drive I'd want /dev/hda to be hd0.
>
> Yes, you can edit it, but you either name the SATA drive as hd0 or the
> IDE, you don't edit that between boots, you have the grub.conf where you
> tell what to boot from where and you can "rename" the hard drives there
> too, this is needed if you have microsoft on a secondary hard drive
> (microsoft is a bit stupid and wants only boot from hd0).
>
>
>> But in my case /dev/sda and /dev/sdb will be part of a raid1 array.
>> So grub won't use /dev/sdb unless /dev/sda fails and I point my bios to
>> boot /dev/sdb (which now becomes sda!) I'd have to install grub onto
>> both disks but the device mapping might be different?
>
> If you only have the root filesystem on the SATA raid, then you don't
> have to name the harddrives for grub, as at that point it's the kernel
> who has taken over things.
>
>
>> I don't think grub knows about raid and boots off the raw disk, the raid
>> array being established AFTER the kernel loads off the raw disk.
>
> Easiest is always to have /boot on it's own slice which is a standard
> non raided filesystem. I'm really not that sure about the raid, I never
> use it myself, but in theory grub could be able to read the hardware
> raided device, but not softraided, than you need the kernel for.
>
Raid1 isn't a problem for grub. Because I have three disks, two sata in
raid and one ide from my current install I need to know how to tell grub
where the root (kernel) is located. Also I'd like the sata disks to be
hd0 when I boot from the sata raid and the ide to be hd0 if I boot from
the ide. I change the boot disk in the bios of course. Eventually I'll
probably remove the IDE disk and just use the sata raid disks since the
raid1 pair will hold 320gb and the ide drive is only 80.

ken scharf wrote:

> Raid1 isn't a problem for grub. Because I have three disks, two sata in
> raid and one ide from my current install I need to know how to tell grub
> where the root (kernel) is located.

Assume your raid is /dev/md0

in device.map
(hd0) /dev/md0
(hd1) /dev/hda

in grub.conf
boot=/dev/md0
title Linux on Raid
root (hd0,0)
kernel /kernel-2.6.20 root=/dev/md0
initrd /initrd-2.6.20.img

title Linux on IDE
root (hd1,0)
kernel /kernel-2.4.33 root=/dev/hda2
initrd /initrd-2.4.33.img

> Also I'd like the sata disks to be
> hd0 when I boot from the sata raid and the ide to be hd0 if I boot from
> the ide.

I don't see the point why both has to be hd0, if you must, then you have to
select boot order in the BIOS each time and have it's own grub installed on
both of the MBR's, but thats just stupid. The best solution is to have one
/boot and keep all the kernels and initrd images there.


--

//Aho

J.O. Aho wrote:
> ken scharf wrote:
>
>> Raid1 isn't a problem for grub. Because I have three disks, two sata in
>> raid and one ide from my current install I need to know how to tell grub
>> where the root (kernel) is located.
>
> Assume your raid is /dev/md0
>
> in device.map
> (hd0) /dev/md0
> (hd1) /dev/hda
>
> in grub.conf
> boot=/dev/md0
> title Linux on Raid
> root (hd0,0)
> kernel /kernel-2.6.20 root=/dev/md0
> initrd /initrd-2.6.20.img
>
> title Linux on IDE
> root (hd1,0)
> kernel /kernel-2.4.33 root=/dev/hda2
> initrd /initrd-2.4.33.img
>
>> Also I'd like the sata disks to be
>> hd0 when I boot from the sata raid and the ide to be hd0 if I boot from
>> the ide.
>
> I don't see the point why both has to be hd0, if you must, then you have
> to select boot order in the BIOS each time and have it's own grub
> installed on both of the MBR's, but thats just stupid. The best solution
> is to have one /boot and keep all the kernels and initrd images there.
>
>
Normally correct. However in the event that one of the disks and or
controllers fail I can still boot via the other disk by changing the
bios boot order. What I meant was that I wanted to have the option of
forcing a boot via the MBA of the IDE disk should the raid array fail
(or visa versa).