[wellylug] DD no go

David Chord gnome at gnome.co.nz
Sat Apr 5 23:45:26 NZDT 2008


Hi

> >  Command line is dd if=/dev/sda of=/dev/sdb

> >  Error is "dd: writing to `/dev/sdb' : Input/output error


> >  After the 2nd time I formatted sdb to fat32 (was a blank disk on the
> > first run), no luck.
>
> First of all, you shouldn't format a DISK device (e.g. sdb) at all -
> you should only ever format PARTITIONS (which are subdivisions of a
> disk, e.g. sdb1, sdb2). That said, if you dd to the disk device you
> overwrite anything that was there anyway, so it's redundant formatting
> it with anything.

Sorry. I formatted SDB1, as a single partition.

Am aware that dd overwrites, supposedly.. But dd doesn't want to run, is 
complaining about not being able to write to the disk. Well, maybe it's 
choking on something so a format will hopefully do a bad sector scan, and 
fix/mark out any bad sectors.,

> Thirdly, there's nothing special that comes to mind about the number
> 4298739712, in case you were wondering.

Sorry, used to dealing with tech support with certain firms who won't help you 
unless you give absolutely every single little detail of the error/messages, 
just in case the window title or something is somehow important to helping 
them.. (Usually the other way round with a certain business software firm 
these days)

> Stated for clarity: a record size is 512 bytes (by default).

> Try this and see if it does the same thing (make sure your 'of' device
> is correct as it will overwrite anything there!):
>
> # dd if=/dev/zero of=/dev/sdb seek=8395975 count=5

Same error, 2+0 in 1+0 out, 512 bytes copied.

> That skips to somewhere near the place you have a problem, so it won't
> take so long to fail if it's going to.
> Might be worth trying to write beyond that sector too:
>
> # dd if=/dev/zero of=/dev/sdb seek=8395978 count=100

Also fails. But if I skip along a bit further, it starts to go again. So some 
sort of damage? How do I fix that? (Ah yes, now I recall why I formatted it - 
when I tried to check the disk for errors, libparted gave a "grow filesystem 
to fill partition" message right before failing - I thought formatting it 
might help it work and maybe find/deal with the errors for me)

> I'd be worried about the integrity of your backup device...

> Can you try a different destination disk?

Nope. Disk is "cheap" by some peoples standards.. But not mine atm :(  
Unfortunaltey this disk is my only current backup option.. 

Have tried reformatting to ext2 and running a disk check, which gave no errors 
(but somehow I doubt it did a surface scan), and tried to run it again - 
still failed at 4.3 gig.. 

(I don't know how to get a check done on un-allocated space, which is why I 
format, in case anyone wants to ask...)

Thanks and bye for now,
David




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