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Old 04-04-2012, 10:57 AM
Karanbir Singh
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 04/04/2012 11:46 AM, Emmanuel Noobadmin wrote:
> just does not seem to be able to find the USB drives. e.g. commands
> like root (hd0,0) just says device not found. This is despite grub

hd0,0 represents the bios device id, are you sure thats what your bios
thinks the usb disk is at ?

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Old 04-04-2012, 04:38 PM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 4/4/12, Karanbir Singh <mail-lists@karan.org> wrote:
> On 04/04/2012 11:46 AM, Emmanuel Noobadmin wrote:
>> just does not seem to be able to find the USB drives. e.g. commands
>> like root (hd0,0) just says device not found. This is despite grub
>
> hd0,0 represents the bios device id, are you sure thats what your bios
> thinks the usb disk is at ?

I can't be sure which is part of the problem. Because when I read the
grub documentation, it said that hitting tab at the prompt after
typing the command will produce a list of possible devices/drives.
However, in my case, nothing happens which seemingly implies grub
could not find any device.

I also did try manually doing (hd0,1), (hd1,0) but none of it seemed
to be a "findable" device. For what it's worth, the installer did see
them as sda and sdb. I also disabled the onboard SATA controller
during my attempts in order to eliminate it from showing up as a
possible device, since grub doc says the (hdx,x) number usually
matches the order in which the devices were discovered.
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Old 04-07-2012, 09:51 AM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 4/5/12, Lamar Owen <lowen@pari.edu> wrote:
> The grub order and names and the linux kernel/udev order and names should
> not be assumed to have any correlation of any kind, since they are
> discovered differently.

Yes, that is what I understand from the grub manual. However, from
that I also understand and expect the first and only device grub could
find would be hd0

> If you can boot a USB live media on this box, you could bring up a grub
> shell and see how grub sees the disks from that (at a root prompt, type
> 'grub' and you'll be greeted with the grub shell, and then you can do
> detection or whatever from that). This also works in the rescue environment
> given by the install media; you do want to do a 'chroot /mnt/sysimage' in
> that shell before entering the grub shell, though.

I've done this previously from the rescue environment but got no
closer to resolving this.

I've tried it again with a default install of CentOS 6.2, using
default drive layout and all.
On first boot, I get the grub shell but I have not been able to find
any command that would list valid devices grub can find, apart from
the tab button.

Rebooting into the rescue environment, chrooting into the drive,
grub-install generates the map to hd(0) which was expected. Runing
grub shell and trying root (hd0) also works.

However, rebooting after updating the grub device map always results
in "Booting from local disk... Error 21" which indicates grub couldn't
find the drive specified.

Any ideas how I can probe/list devices within grub shell? I've done
the stupid method of root(hd0,x) all the way up to root(hd8,3) without
luck.
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Old 04-10-2012, 06:19 AM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

In trying to solve this problem, I came across these two articles
regarding GRUB and USB booting.

http://vlinux-freak.blogspot.com/2011/01/how-to-create-grub-boot-floppy-usb.html
http://bootloader.wikidot.com/linux:boot:usb-grub

The floppy drive issue appears to be the situation as booting the
rescue environment from a USB DVD does show up as /dev/fd0.

However, the solutions in those articles did not work. In the first,
the GRUB command/options are different, although changing the option
from boot-directory to root-directory appear to work, there was no
option to force floppy drive.

In the second, the python script thinks the grub install has already
been patched for floppy boot so couldn't do anything.

I've also tried editing menu.lst to use (fd0) but also didn't work.
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Old 04-10-2012, 11:19 AM
Phil Schaffner
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

Emmanuel Noobadmin wrote on 04/07/2012 05:51 AM:
>
> Any ideas how I can probe/list devices within grub shell? I've done
> the stupid method of root(hd0,x) all the way up to root(hd8,3) without
> luck.
>

Have you tried the grub "find" command?
find /grub/stage1
find /boot/grub/stage1
etc.

http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB

Phil

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Old 04-10-2012, 11:47 AM
Patrick DERWAEL
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

Emmanuel,
I used a totally different approach by using VMware: the trick is to
install on a physical device which is the USB drive.
When the installation requests a reboot, simply boot on your USB and off
you go!

2012/4/10 Phil Schaffner <Philip.R.Schaffner@nasa.gov>

> Emmanuel Noobadmin wrote on 04/07/2012 05:51 AM:
> >
> > Any ideas how I can probe/list devices within grub shell? I've done
> > the stupid method of root(hd0,x) all the way up to root(hd8,3) without
> > luck.
> >
>
> Have you tried the grub "find" command?
> find /grub/stage1
> find /boot/grub/stage1
> etc.
>
> http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB
>
> Phil
>
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
>



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Old 04-10-2012, 03:28 PM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 4/10/12, Phil Schaffner <Philip.R.Schaffner@nasa.gov> wrote:

> Have you tried the grub "find" command?
> find /grub/stage1
> find /boot/grub/stage1
> etc.
>
> http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB

I'm deeply embarrassed and stunned by why I did not stumble across
that googling or how I could miss seeing the command in grub shell and
doc. I'll try this the next time I get to that machine again.

Thank you very much!
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Old 04-10-2012, 03:31 PM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 4/10/12, Patrick DERWAEL <patrick@derwael.be> wrote:
> Emmanuel,
> I used a totally different approach by using VMware: the trick is to
> install on a physical device which is the USB drive.
> When the installation requests a reboot, simply boot on your USB and off
> you go!

That is pretty much what I did. Boot DVD 1 with a USB DVD drive,
install to /dev/sda which is the USB flash drive. When the
installation requests a reboot, shutdown, remove as well as leave the
DVD drive around and reboot... and only grub prompt or Error 21.

Maybe there's a minor but critical step I'm missing so I'll appreciate
it if you could outline in greater details how you did it.

I've tried installing grub to both MBR i.e. /dev/sda as well as first
partition /dev/sda1 but neither works.
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Old 04-10-2012, 03:34 PM
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

Emmanuel Noobadmin wrote:
> On 4/10/12, Patrick DERWAEL <patrick@derwael.be> wrote:
>> Emmanuel,
>> I used a totally different approach by using VMware: the trick is to
>> install on a physical device which is the USB drive.
>> When the installation requests a reboot, simply boot on your USB and off
>> you go!
>
> That is pretty much what I did. Boot DVD 1 with a USB DVD drive,
> install to /dev/sda which is the USB flash drive. When the
> installation requests a reboot, shutdown, remove as well as leave the
> DVD drive around and reboot... and only grub prompt or Error 21.
>
> Maybe there's a minor but critical step I'm missing so I'll appreciate
> it if you could outline in greater details how you did it.
>
> I've tried installing grub to both MBR i.e. /dev/sda as well as first
> partition /dev/sda1 but neither works.

Two questions: a) are you sure that the USB key is /dev/sda, and b) does
your system offer a boot menu, or only go into setup to tell it to boot
off the USB key?

Oh, and in fdisk, is the partition flagged bootable?

mark

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Old 04-12-2012, 04:59 PM
Emmanuel Noobadmin
 
Default Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

On 4/10/12, m.roth@5-cent.us <m.roth@5-cent.us> wrote:
> Two questions: a) are you sure that the USB key is /dev/sda,
Yes, I've verified this before and again after you asked that it is
seen as /dev/sda, at least through the installation DVD. fdisk also
does not find a sdb/c/d if I try that.

>and b) does your system offer a boot menu, or only go into setup to tell it to boot
> off the USB key?

Both, I can set the boot sequence in BIOS, which is currently to boot
USB first. And I can also hit F10 to choose.

> Oh, and in fdisk, is the partition flagged bootable?
Yes, definitely
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