Re: Kernel panic : VFS : unable to mount root fr on 03:05

Theodore Y. Ts'o (tytso@mit.edu)
Fri, 18 Oct 1996 09:03:59 -0400


Date: Fri, 18 Oct 1996 11:53:01 +0200
From: stephane@lituus.fr (Stephane Legrand)

When i restart the PC, i discovered that Linux don't boot (see the error
message below) AND Windows 95 don't boot also !!

...
hda: read_intr : status = 0x51 {DriveReady SeekComplete Error}
hda: read_intr : error = 0x04 {DriveStatusError}
...

You know, even though Windows 95's error message isn't much better:

DRIVE NOT READY ERROR
Insert BOOT diskette in A:
Press any key when ready

Perhaps in 2.1 we should work on making some error messages a bit more
comprehensible to users? For example something like:

hda: hardware disk failure: <current debugging information>

might help many confused users figure out what the heck is going on.
I've gotten (and linux-kernel has also gotten) a lot of questions about
users not understanding what's going wrong when they start seeing those
messages. I will admit that I'm baised, because since the disk is going
bad, there is also the presumption by users that it's an ext2 problem,
when in reality there's very little we can do when the hard disk is
going kaput.

Stephane, the problem is that your hard disk has developed a bad spot in
a very critical place --- in the partition table of your main disk, to
be specific. There's little you can do to recover from this situation,
except to get the disk replaced.

There's one very last ditch thing you can try doing, which is to remap
the bad block --- *IF* your disk's hardware supports that. Boot a Linux
repair disk, and then try running the command:

dd if=/dev/zero of=/dev/hda bs=1k count=1

This will *wipe out* your partition table, but it's already been wiped
out because of a disk failure on this block. If you're lucky though,
your hard disk *may* remap the block. If so, you will be able to
recreate your partition table using fdisk (again, use the one off of
your Linux hard disk). This assumes that you know the original
partition layout; if you do not, you may have to reinstall from
scratch. (Which you would have had to do anyway; this procedure is
basically a last ditch attempt to try to save you a little money by not
requiring you to replace the disk.)

If you think this is too complicated, you can do what the Microsoft
support people probably would tell you --- just replace the disk
outright. Actually, if you have the money, that's probably the safer
course of action, actually. Once a disk starts developing a bad block
or two, the chances are very much higher that it will develop more bad
blocks, and then very shortly thereafter, fail catastrophically.

Good luck.

- Ted