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Hi all,
I have an external disk with Linux, and Windows on the internal disk
of my laptop. I have GRUB installed on the external disk, so I can
boot either Linux or Windows. This used to work just fine.
Lately I have been having lots of problems in loading GRUB. Most of
the time it doesn't load and the machine just boots Windows from the
internal disk. It seems to be getting worse with time.

When I boot another linux on a different machine, I can read and write
on this external disk, so the disk is not broken. I don't think it's
a problem with the BIOS either (boot order seems fine, plus I tried
with another laptop and got the same problem).

Questions (I've googled around but I still can't figure them out):

1. could it be a software problem with the MBR? If so, how do I fix
it?

2. if it's a hardware problem (heads cannot read the MBR?), is it
possible to install GRUB on a USB key and from the USB key boot
Linux on the external disk and Windows on the internal disk?

3. If the answer to 2. is yes, how do I do it? For example, should I
reformat the USB key?


Thank you.

"eric" <questermocolle@hotmail.com> wrote
> Hi all,
> I have an external disk with Linux, and Windows on the internal disk
> of my laptop. I have GRUB installed on the external disk, so I can
> boot either Linux or Windows. This used to work just fine.
> Lately I have been having lots of problems in loading GRUB. Most of
> the time it doesn't load and the machine just boots Windows from the
> internal disk. It seems to be getting worse with time.

The problem is unlikely to be time-related. Either the machine boots from
the external disk or it doesn't. If it does so but only intermittently, the
problem is far more likely to be cable-related than anything to do with the
contents of the MBR or the disk itself. IME of course.

> When I boot another linux on a different machine, I can read and write
> on this external disk, so the disk is not broken. I don't think it's
> a problem with the BIOS either (boot order seems fine, plus I tried
> with another laptop and got the same problem).

So you cannot boot from this disk at all? Or you can on another machine? Or
it boots intermittently on either machine?

> Questions (I've googled around but I still can't figure them out):
>
> 1. could it be a software problem with the MBR? If so, how do I fix
> it?

I guess it's not impossible. You fix it by re-installing GRUB to that MBR
(grub /dev/sdx where sdx is the external disk).

> 2. if it's a hardware problem (heads cannot read the MBR?), is it
> possible to install GRUB on a USB key and from the USB key boot
> Linux on the external disk and Windows on the internal disk?

AFAICT there is no way to do this, because when GRUB is run from the USB
key, it is only aware of the USB device, so it cannot boot a partition on
another device. This could be wrong - but I have never seen or heard of a
solution.

You could consider installing GRUB on the laptop's *internal* disk though.
It should then offer you the ability to boot from either disk, as you
choose. This would not solve the problem of why you can no longer boot
(consistently) from the external disk, but would work around it.

CC

On Mar 19, 3:04 pm, "Magnate" <n...@receiving.here> wrote:
> "eric" <questermoco...@hotmail.com> wrote
>
> > Hi all,
> > I have an external disk with Linux, and Windows on the internal disk
> > of my laptop. I have GRUB installed on the external disk, so I can
> > boot either Linux or Windows. This used to work just fine.
> > Lately I have been having lots of problems in loading GRUB. Most of
> > the time it doesn't load and the machine just boots Windows from the
> > internal disk. It seems to be getting worse with time.
>
> The problem is unlikely to be time-related. Either the machine boots from
> the external disk or it doesn't. If it does so but only intermittently, the
> problem is far more likely to be cable-related than anything to do with the
> contents of the MBR or the disk itself. IME of course.
>

Thanks a lot for your reply. I was able to load GRUB on the external
disk on two other
machines. I only made one attempt on each machine and it worked for
both, while on
the laptop it's still intermittent. I begin to think it's a power
problem, namely the USB
port doesn't give enough power to the disk at the beginning. I tried
also to use the
extra USB power cable (in addition to the data cable) but it's still
intermittent.


> > When I boot another linux on a different machine, I can read and write
> > on this external disk, so the disk is not broken. I don't think it's
> > a problem with the BIOS either (boot order seems fine, plus I tried
> > with another laptop and got the same problem).
>
> So you cannot boot from this disk at all? Or you can on another machine? Or
> it boots intermittently on either machine?

See above.
>
> > Questions (I've googled around but I still can't figure them out):
>
> > 1. could it be a software problem with the MBR? If so, how do I fix
> > it?
>
> I guess it's not impossible. You fix it by re-installing GRUB to that MBR
> (grub /dev/sdx where sdx is the external disk).
>
> > 2. if it's a hardware problem (heads cannot read the MBR?), is it
> > possible to install GRUB on a USB key and from the USB key boot
> > Linux on the external disk and Windows on the internal disk?
>
> AFAICT there is no way to do this, because when GRUB is run from the USB
> key, it is only aware of the USB device, so it cannot boot a partition on
> another device. This could be wrong - but I have never seen or heard of a
> solution.
>

I was under the impression that once GRUB is loaded into the computer
memory,
it doesn't matter where it was residing. For example when I manage to
load GRUB
residing on the ext. disk, I can boot the Windows installation
residing on the internal disk.
Am I missing something?

Thanks again.

> You could consider installing GRUB on the laptop's *internal* disk though.
> It should then offer you the ability to boot from either disk, as you
> choose. This would not solve the problem of why you can no longer boot
> (consistently) from the external disk, but would work around it.
>
> CC

On Mar 19, 3:04 pm, "Magnate" <n...@receiving.here> wrote:
> "eric" <questermoco...@hotmail.com> wrote
>
> > Hi all,
> > I have an external disk with Linux, and Windows on the internal disk
> > of my laptop. I have GRUB installed on the external disk, so I can
> > boot either Linux or Windows. This used to work just fine.
> > Lately I have been having lots of problems in loading GRUB. Most of
> > the time it doesn't load and the machine just boots Windows from the
> > internal disk. It seems to be getting worse with time.
>
> The problem is unlikely to be time-related. Either the machine boots from
> the external disk or it doesn't. If it does so but only intermittently, the
> problem is far more likely to be cable-related than anything to do with the
> contents of the MBR or the disk itself. IME of course.
>
> > When I boot another linux on a different machine, I can read and write
> > on this external disk, so the disk is not broken. I don't think it's
> > a problem with the BIOS either (boot order seems fine, plus I tried
> > with another laptop and got the same problem).
>
> So you cannot boot from this disk at all? Or you can on another machine? Or
> it boots intermittently on either machine?
>
> > Questions (I've googled around but I still can't figure them out):
>
> > 1. could it be a software problem with the MBR? If so, how do I fix
> > it?
>
> I guess it's not impossible. You fix it by re-installing GRUB to that MBR
> (grub /dev/sdx where sdx is the external disk).
>
> > 2. if it's a hardware problem (heads cannot read the MBR?), is it
> > possible to install GRUB on a USB key and from the USB key boot
> > Linux on the external disk and Windows on the internal disk?
>
> AFAICT there is no way to do this, because when GRUB is run from the USB
> key, it is only aware of the USB device, so it cannot boot a partition on
> another device. This could be wrong - but I have never seen or heard of a
> solution.
>
> You could consider installing GRUB on the laptop's *internal* disk though.
> It should then offer you the ability to boot from either disk, as you
> choose. This would not solve the problem of why you can no longer boot
> (consistently) from the external disk, but would work around it.
>
> CC

New evidence it's a power problem:
if I plug the additional USB power cable into the laptop, the ext
disk works (very) intermittently.
HOWEVER, if I plug the USB data cable in the laptop and the additional
USB power cable
into a desktop computer, the laptop IS able to start GRUB. I tried
three times and got
100% success.

How can I solve the problem of the insufficient power (assuming this
is really what's going on?) other than plugging the power cable into
another computer
(which clearly defeats the point of having a laptop in the first
place).

On 2008-03-20, eric <questermocolle@hotmail.com> wrote:
>
>
> New evidence it's a power problem:
> if I plug the additional USB power cable into the laptop, the ext
> disk works (very) intermittently.
> HOWEVER, if I plug the USB data cable in the laptop and the additional
> USB power cable
> into a desktop computer, the laptop IS able to start GRUB. I tried
> three times and got
> 100% success.
>
> How can I solve the problem of the insufficient power (assuming this
> is really what's going on?) other than plugging the power cable into
> another computer
> (which clearly defeats the point of having a laptop in the first
> place).
>
Get a powered USB hub.

On Mar 20, 9:33 pm, Bill Marcum <marcumb...@bellsouth.net> wrote:
> On 2008-03-20, eric <questermoco...@hotmail.com> wrote:
>
>
>
> > New evidence it's a power problem:
> > if I plug the additional USB power cable into the laptop, the ext
> > disk works (very) intermittently.
> > HOWEVER, if I plug the USB data cable in the laptop and the additional
> > USB power cable
> > into a desktop computer, the laptop IS able to start GRUB. I tried
> > three times and got
> > 100% success.
>
> > How can I solve the problem of the insufficient power (assuming this
> > is really what's going on?) other than plugging the power cable into
> > another computer
> > (which clearly defeats the point of having a laptop in the first
> > place).
>
> Get a powered USB hub.

Thanks. As soon as I posted the last post I realized that a powered
USB hub had to
exist, so I went out and bought one. Duh. Now everything works.