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This command produced the error mentioned above after 9 h (preparing a 2 TB hdd for encryption):

time openssl enc -aes-256-ctr -pass pass:"$(dd if=/dev/urandom \
bs=128 count=1 2>/dev/null | base64)" -nosalt </dev/zero \
| pv -bartpes 1884183960000  | dd bs=512 count=1840023391 of=/dev/sdc3

I got at 50% (9 h) a total written GB count as well as a bs/count information.

Is it possible to resume this process?

1 Answer 1

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I think you need the seek=BLOCKS which should make dd start writing at the block next to BLOCKS of your disk address space.

Supposedly you should also decrease count by that number of blocks as well.

10
  • You again. And another perfect answer for me. TYSM all the best from a German questioner.
    – John Jane
    Feb 27, 2015 at 20:06
  • I found another explanation regarding my question to obs/ibs: unix.stackexchange.com/questions/108858/… What I didn't found was a real difference between bs and obs/ibs together with seek. The man isn't clear frmpov.
    – John Jane
    Feb 27, 2015 at 20:23
  • I found something about seek/skip: skip=SKIPBLOCKS | Skip blocks (bs/ibs) of the INPUT-device(!) seek=SEEKBLOCKS | Skip blocks (bs/obs) of the OUTPUT-device(!)
    – John Jane
    Feb 27, 2015 at 20:37
  • @JohnJane, keep in mind that your source device is not really a device but rather a stream: skipping N bytes from it would litreally mean reading them (or failing with "blah blah the device is not seekable" -- depending on how smart dd is; both cases are unacceptable. In either case, skipping a part of random input has no sense. Seeking in the destination device, conversely, has sense: it will position the file pointer to the correct address using appropriate syscall.
    – kostix
    Feb 27, 2015 at 22:56
  • Yes, I am aware of that. But I run into the same error after 9 h (50%) again today. Would you do me a favor and try to replicate the dd values to check if I may use/calculated the wrong ones?
    – John Jane
    Feb 28, 2015 at 9:23

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