4 ms·

You can use head as stated in the article: sudo dd if=/dev/sda of=/tmp/boot.1 bs=512 count=1 sudo head -c 512 /dev/sda > /tmp/boot.2 md5sum /tmp/boot.1 06d6

• merlincorey 4y ago
  You missed a nuance in the GP's problem set: > dd if=random-linux-image.img of=/dev/mmcblk0 bs=512 count=62499 seek=1 skip=1 is not the same as: > sudo dd if=/dev/sda of=/tmp/boot.1 bs=512 count=1 You are missing the "seek" and "skip" arguments which the GP challenges you to make `head` do.
  • fbn79 4y ago
    You right. To skip you can pipe tail. sudo head -c 1024 /dev/sda | tail -zc 512 > /tmp/boot.2 Read 1024, keep last 512
    • jstimpfle 4y ago
      What if the position is not at 512 but at 512G?
      • fbn79 4y ago
        Not tested, by I think the performance will be in the same order. Would be nice to do a benchmark test.
        • jstimpfle 4y ago
          No, it is O(n) vs O(1). Why would you read 512G + 512 bytes if you only need to read 512 bytes at offset 512G?
          • fbn79 4y ago
            I think you can just invert and do tail first sudo tail -zc +513 /dev/sda | head -c 512 > /tmp/boot.2
            • jstimpfle 4y ago
              Well now you're seeking to the offset (tail is).
• knorker 4y ago
  That "sudo head" only works for reading, not writing though. I use dd when redirect doesn't have permission.
  • guenthert 4y ago
    I've seen tee used for that, but I myself stick to dd (out of habbit or because I belong to said cult).