fdisk /mbr vs fixmbr ??

  • Thread starter Thread starter jameshanley39
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jameshanley39

after a power cut, win2k pro said "inaccessible boot device".

fdisk /mbr did not fix it

fixmbr did. I didn't get the error after fixmbr. Fixmbr did say it
"detected" an "invalid" err something.

Since it started windows, and the MBR is before that. It indicates
that fixmbr does a lot more good stuff (perhaps NT specific?) than
just replacing the MBR.

anybody got any explanation?
 
after a power cut, win2k pro said "inaccessible boot device".
Click to expand...

First, did you power off the system and leave it sit for
awhile disconnected from AC (I mean a couple minutes or so)?
A power outtage should not have touched the MBR, it would
seem more likely the system was just experiencing a glitch
in operation as when power comes back on it can be poor
quality power than jams up things until power is cut and
restored while that power is in a better state.

I'm just wondering if you needed to do anything to it, and
if so, why it happened.

fdisk /mbr did not fix it

fixmbr did. I didn't get the error after fixmbr. Fixmbr did say it
"detected" an "invalid" err something.
Click to expand...

I think you forgot the imporant detail, something.

Since it started windows, and the MBR is before that. It indicates
that fixmbr does a lot more good stuff (perhaps NT specific?) than
just replacing the MBR.

anybody got any explanation?
Click to expand...

Not why you needed to do anything to your MBR, but

http://support.microsoft.com/kb/166454
 
after a power cut, win2k pro said "inaccessible boot device".

fdisk /mbr did not fix it

fixmbr did. I didn't get the error after fixmbr. Fixmbr did say it
"detected" an "invalid" err something.

Since it started windows, and the MBR is before that. It indicates that
fixmbr does a lot more good stuff (perhaps NT specific?) than just
replacing the MBR.

anybody got any explanation?
Click to expand...

Fix /mbr places a blank mbr on the disk

Fixmbr probably replaces the master mbr record form the backup copy of
the master mbr record.
 
First, did you power off the system and leave it sit for
awhile disconnected from AC (I mean a couple minutes or so)?
A power outtage should not have touched the MBR, it would
seem more likely the system was just experiencing a glitch
in operation as when power comes back on it can be poor
quality power than jams up things until power is cut and
restored while that power is in a better state.

I'm just wondering if you needed to do anything to it, and
if so, why it happened.





I think you forgot the imporant detail, something.





Not why you needed to do anything to your MBR, but

http://support.microsoft.com/kb/166454
Click to expand...

at no point did I disconnect the power wait a few min and reconnect
it. To get the so-called "clean power" that you speak of.

I never disconnected the power. I got the error, restarted a few times
by holding the power button to turn off. Tapping it to turn on.

Each time I got the error.

I did fdisk /mbr, still got the error. Each time restarting.

Did fixmbr, it said it detected an invalid something or other. .
Restarted, bam, worked.

The error that occurred most probably was not a sudden glitch, it
occurred straight after the power cut. It was fine before.

It's a low level thing.. so difficult to say why it fixed it. That's
fixmbr. An fdisk /mbr story - and demo of this low level thing. I
knew a girl that got water in her laptop. She called the techies. One
came along and I thought he'd say "fdisk /mbr".. I said "you really
think fdisk /mbr will work ?!!" He said "oh yeah, it fixes
everything!" . We agreed it was worth a try. It worked! Her computer
wasn't starting before, and then it did.
 
after a power cut, win2k pro said "inaccessible boot device".

Tweak your BIOS to perform a self-test. I find with my Win 2K Pro machine
the extra ~15 second delay during the self-test allows everything to proceed
as expected.

PS Doesn't fdisk /mbr wipe the disk of the label of the OS, meaning that
you'll then get the more serious and dreaded message "Unable to find OS",
meaning that without a lot of hard work, you'll probably have to re-install
Windows?!
Your initial reaction I must say sounds a bit gungho!
 
Tweak your BIOS to perform a self-test. I find with my Win 2K Pro machine
the extra ~15 second delay during the self-test allows everything to proceed
as expected.
Click to expand...

interesting idea, I haven't tried it, but my solution wasn't a
workaround(however your workaround works?). Mine doesn't slow down
startup
PS Doesn't fdisk /mbr wipe the disk of the label of the OS, meaning that
you'll then get the more serious and dreaded message "Unable to find OS",
meaning that without a lot of hard work, you'll probably have to re-install
Windows?!
Your initial reaction I must say sounds a bit gungho!
Click to expand...

No, it's BEFORE lots of things. Before the OS. The master boot record
doesn't know / store anything about the OS. It is harmless.

The only time i've ever heard of it being harmful - making data
inaccessible! - is in some weird circumstance that i've never
encountered, and neither has anybody I know. I think the circumstance
is when the partition is encrypted or something.

It's not gungho at all. It's very safe. It's actually more gungho to
do the next possibilities, such as backing up all the data(asking the
whole family where they keep their data). holding your breath.
Reinstalling windows or doing a windows repair(safer regarding
data!).. It's hours.

This is 2min and safe. Though I did chkdsk after it (a bit
iunnecessary since windows did it anyway. I just didn't know what
switch windows used, so I did /r myself)

Here are 2 links I read a little of a while back. I didn't understand
them all but they helped.

I'm far from an expert and i'm probably wrong but i'll try

The MBR is on a hard drive with a partition one might intend to boot
off of. It looks for the Active partition.

I guess it is exactly the same regardless of your OS (or, differences
are irrelevant). Hence win98's fdisk /mbr doesn't write one that only
works for windows 98. It will work for windows xp too, and probably
linux. There may be different ways to write the MBR, and different OSs
have utilities to do it different ways, but they are all doing the
same function, and are interchangeable.

here are 2 links

Disassembly of a Master Boot Record (MBR)
http://www.ata-atapi.com/hiwmbr.htm

Troubleshooting the startup process (windows xp resource kit)
http://www.microsoft.com/technet/prodtechnol/winxppro/reskit/c29621675.mspx
 
interesting idea, I haven't tried it, but my solution wasn't a
workaround(however your workaround works?). Mine doesn't slow down
startup
Click to expand...

You can normally press esc or some other button during the self-test - the
idea being that for whatever reason the timing's out and the extra second or
two it takes to start a self-test is all it takes to resolve this issue.
No, it's BEFORE lots of things. Before the OS. The master boot record
doesn't know / store anything about the OS. It is harmless.
Click to expand...

I wouldn't say it was harmless! If you didn't have one, your computer would
just be a big metal box with flashing lights! The MBR is an area on the
physical disk that contains a record of where to look for the OS(es)
installed. If that record is lost / wrongly altered / destroyed, then you
effectively have to wipe the disk and start again.
It's not gungho at all. It's very safe.
Click to expand...
This is 2min and safe. Though I did chkdsk after it (a bit
iunnecessary since windows did it anyway. I just didn't know what
switch windows used, so I did /r myself)
Click to expand...

If you don't know what a command does in relation to the MBR, my advice is
to leave well alone until someone can explain properly what the command
does. If you have a multi-booting machine for instance, a "very safe", "2
minute" play with some randomly generated command can effectively destroy
the setup, in the process ruining hours of configuration. And yes, you may
be able to tell, I speak from experience!
 
You can normally press esc or some other button during the self-test - the
idea being that for whatever reason the timing's out and the extra second or
two it takes to start a self-test is all it takes to resolve this issue.



I wouldn't say it was harmless! If you didn't have one, your computer would
just be a big metal box with flashing lights!
Click to expand...

you didn't understand what I was saying

Besides. As useless as a trying to boot a computer off a disk with no
MBR is. I don't see why you consider such a metal box with flashing
lights useless, since your head is clearly only a box with a pair of
eyeballs in it.
The MBR is an area on the
physical disk that contains a record of where to look for the OS(es)
installed. If that record is lost / wrongly altered / destroyed, then you
effectively have to wipe the disk and start again.
Click to expand...

As has been said.
fdisk /mbr or FIXMBR rewrites the MBR . It does not wipe the disk.

It sounds like you've never done it.
If you don't know what a command does in relation to the MBR, my advice is
to leave well alone until someone can explain properly what the command
does. If you have a multi-booting machine for instance, a "very safe", "2
minute" play with some randomly generated command can effectively destroy
the setup, in the process ruining hours of configuration. And yes, you may
be able to tell, I speak from experience!
Click to expand...

I know many people with lots of experience in screwing their computer
up. They're smart enough not to offer advice. They are more likely to
ask me for my advice.

If you even claim to have experience in screwing it up, give me an
example of when you've screwed it up.

It sounds like you've screwed up lots of things and so you've been
afraid of running fdisk /mbr or FIXMBR. So you assume you'd screw it
up, and your arrogance makes you think that everybody else would too.

I'd put it to you that even you wouldn't be able to screw up a
computer with those commands.
 
I wouldn't say it was harmless! If you didn't have one, your computer
you didn't understand what I was saying

Besides. As useless as a trying to boot a computer off a disk with no
MBR is. I don't see why you consider such a metal box with flashing
lights useless, since your head is clearly only a box with a pair of
eyeballs in it.
Right...

As has been said.
fdisk /mbr or FIXMBR rewrites the MBR . It does not wipe the disk.
Click to expand...

I clearly said that if the mbr is mangled, you effectively have to wipe the
disk, i.e., reinstall the operating system again. At no point did I say that
it wiped the disk.
If you even claim to have experience in screwing it up, give me an
example of when you've screwed it up.

It sounds like you've screwed up lots of things and so you've been
afraid of running fdisk /mbr or FIXMBR. So you assume you'd screw it
up, and your arrogance makes you think that everybody else would too.

I'd put it to you that even you wouldn't be able to screw up a
computer with those commands.
Click to expand...

I will repeat here again that you certainly appear to be gungho with your
rather amateurish attitude to fixing IT problems. Unfortunately you are
making a lot of potentially crucial assumptions about the way a system may
be configured to start with.

For example. if you were to tell someone who has a dual-boot Windows and
Linux OS to "harmlessly" perform the fdisk /mbr command, they run the
possibility of corrupting / deleting their boot manager program and
subsequently may not be able to boot back into either system.

The effectiveness or harmlessness of performing it also depends which upon
which partitions and which drives your OS(es) are on.

Just because you tried it with your system, does not mean that others are
likely to experience no bad side-effects as well. Its rather irresponsible
for you to claim otherwise.

If anyone is reading this debate and is wonder what to believe, my best
advice is to not rush into doing anything that you are unsure about.
Research, research, research.
 
As has been said.
fdisk /mbr or FIXMBR rewrites the MBR . It does not wipe the disk.

It sounds like you've never done it.
Click to expand...


There should never be a reason to rewrite the MBR from the
fault you had. You are describing a solution that is not
universal, and should not have been required. It would be
best to find the cause of the problem now.
 
I clearly said that if the mbr is mangled, you effectively have to wipe the
disk, i.e., reinstall the operating system again. At no point did I say that
it wiped the disk.
Click to expand...

I'm looking at this logically, you tell me where i'm going wrong.
An assumption? Reasoning?

fdisk /mbr rewrites the MBR
FIXMBR rewrites the MBR


You bring up an interesting case of where a user might have to
reinstall windows.. But this time you bring some information to back
yourself up. You suggest that there are boot managers that modify the
MBR. Google agrees with you. I never really got round to meddling with
those.

Interesting

Note-
I think the windows boot manager doesn't touch the MBR. I recall from
a link I mentioned here that it uses NTLDR which reads boot.ini
So,
If a user has no 3rd party boot manager. They install windows on a
system, they even have a few partitions from installing windows a few
times. They use boot.ini (or perhaps it's NTLDR reading boot.ini) as
their boot manager.

If they run fdisk /mbr or fixboot they don't have to reinstall their
operating system.

I've tried this on systems like this, of my own, of friends, family,
clients. And technical friends have tried it on their systems, and
their friends, and thier clients!

I will repeat here again that you certainly appear to be gungho with your
rather amateurish attitude to fixing IT problems. Unfortunately you are
making a lot of potentially crucial assumptions about the way a system may
be configured to start with.

For example. if you were to tell someone who has a dual-boot Windows and
Linux OS to "harmlessly" perform the fdisk /mbr command, they run the
possibility of corrupting / deleting their boot manager program and
subsequently may not be able to boot back into either system.

The effectiveness or harmlessness of performing it also depends which upon
which partitions and which drives your OS(es) are on.

Just because you tried it with your system, does not mean that others are
likely to experience no bad side-effects as well. Its rather irresponsible
for you to claim otherwise.

If anyone is reading this debate and is wonder what to believe, my best
advice is to not rush into doing anything that you are unsure about.
Research, research, research.
Click to expand...

Your example (Boot managers that change the MBR) is interesting. I
haven't tested your claim.
Furthermore, technically, if all the MBR does is chooses the partition
to boot. Then I don't see why windows would need to be reinstalled
after it.

I don't have a problem with your claim if it's a technical claim.
You've got more technical - GOOD. This is a technical newsgroup.

I'm currently questioning your claim. It is not a debate. I'm not
disagreeing with you.

I was only critical of you when you provided no remotely technical
backup for your claim.
 
There should never be a reason to rewrite the MBR from the
fault you had. You are describing a solution that is not
universal, and should not have been required. It would be
best to find the cause of the problem now.
Click to expand...

How do you suggest I do that?

Note: I'm not in front of that machine and won't be for a while. But I
will take note of what you write and try it when I get the
opportunity.
 
fdisk /mbr rewrites the MBR
FIXMBR rewrites the MBR
Click to expand...


fdisk does more than rewrites the code. It also writes a new disk
signature. Windows uses disk and partition signatures to identity drives
and assign drive letteres. So depending on your setup, this can have an
unwanted effect
 
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