Gene Heskett wrote:

On Thu May 1 2003 03:40, Paul Bijnens wrote:

  $ mt compression off
  $ mt status
       (verify compression status and blocksize (0 = var, is
best)) $ dd bs=32k count=10 if=/dev/zero of=/dev/your/tape
  $ amlabel YouConfig OLDLABEL45
      (probably add -f to force)

I use dd to extract the label block, turn the compression off, and dd the label block back to the tape, all using the rewinding version of the device. That way one isn't messing with the old girls mind by calling amlabel, which in turn messes with the tapelist order.

That's indeed a better approach. Thus it becomes something like:

   $ dd bs=32k count=1 if=/dev/st0 of=/tmp/tapelbl
   $ mt -f /dev/st0 compression off
   $ dd bs=32k count=1 if=/tmp/tapelbl of=/dev/st0
   $ mt -f /dev/st0 status

(all comands for Linux and DAT-like tapes and all commands unverified :-)

I just realize that the latest "amtapetype" will also write without reading,
so a "amtapetype -c ..." will fill the first part of your tape with garbage
and keep the hardware compression setting that you just issued before.
The "-c" options takes only a few minutes.