[TUHS] PDP-7 UNIX filesystem

Warner Losh imp at bsdimp.com
Sat Oct 26 08:54:43 AEST 2019

On Fri, Oct 25, 2019, 3:35 PM Arthur Krewat <krewat at kilonet.net> wrote:

> On 10/25/2019 5:08 PM, Michael Kjörling wrote:
> > The only thing resembling "deprecation" of dd that I'm aware of is the
> > recommendation I saw many years ago to not use it to copy potentially
> > problematic storage media (for data recovery), but to use ddrescue for
> > that purpose instead. The reason for this is that with conv=noerror
> > (without which it'd simply abort if it encounters an I/O error), dd
> > would simply skip past data in the input that it can't read, but not
> > adjust any offsets in the output, which wreaks havoc with anything
> > where offsets matter (such as in file system metadata).
> Which is where conv=sync,noerror comes in. Of course, I have no freakin'
> idea what version of UNIX that came into being. ;)

Ddrescue tries multiple times with different sizes, which dd doesn't do.


art k.
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