[linux-lvm] DM: Possible disk corruption?

Jan-Benedict Glaw jbglaw at lug-owl.de
Tue Jan 7 09:50:02 UTC 2003

On Tue, 2003-01-07 14:52:49 +0000, Alasdair G Kergon <agk at uk.sistina.com>
wrote in message <20030107145249.A13660 at uk.sistina.com>:
> On Tue, Jan 07, 2003 at 10:28:50AM +0100, Jan-Benedict Glaw wrote:
> > The first 512 byted of mentioned boot HDD where overwritten by some
> > Samba log! This is followed by some KB of 0x00.
> If you read/write directly to /dev/hda do you see any corruption?

I've not seen any. The system is quite busy at at some time swapping.
Swapspace is on hda so I would have seen killed processes. But despite
not booting at some time, the box is rock solid.

> Do you see any errors for the device in the system logs?


> Nevertheless, you can block LVM2 userspace from reading/writing
> to/from /dev/hda and its partitions by adding a filter to lvm.conf 
> (see example.conf) e.g. "r|^/dev/hda|"
> and then running vgscan to apply the new filter.
> [Personally I recommend using a positive filter though - (a)ccept
> the devices you want to use with LVM2 and (r)eject everything else.]

As the box isn't really productive, I can continue to play with it. I'll
do some DM/LVM activity and occassionally sfdisk -l /dev/hda.

> Did you keep a complete log of the commands you ran so you can check
> retrospectively for typos?  (e.g. "/dev/hda" where "/dev/hda2" was
> intended)  [Always a good idea to set shell history to a big number,
> or (esp. on a shared box) to use 'sudo' to record all commands 
> run as root.]

Sorry, nothing there:
mirror:~# cat .bash_history |egrep '(vg|lv|pv)'
pvdisplay -v |less -S
cat /etc/resolv.conf 

This has been the second scribbled boot sector on this box. Using LVM on
daily basis (and on more than only that one box) I don't think that I
did the same mistake twice.

Well, I have to do some LVM administration in near future, I'll pay
attention to my /dev/hda:-)

Basically, I liked to know if there are known bugs which could have lead
to such a corruption.

Oh, the samba los snipplet should have gone to
/var/log/samba/<some_file_name>, which is on /dev/hda3. /dev/hda2 is
swap and /dev/hda1 is /boot. So the block ended up in a wrong partition,
at a wrong offset but on the right device (hey, at least one out of
three is right:-)

I'll have an eye on it.


   Jan-Benedict Glaw       jbglaw at lug-owl.de    . +49-172-7608481
   "Eine Freie Meinung in  einem Freien Kopf    | Gegen Zensur
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