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C.4.2. Optional: Fill the Device with Random Data

Filling <device> (eg: /dev/sda3) with random data before encrypting it greatly increases the strength of the encryption. The downside is that it can take a very long time.


The commands below will destroy any existing data on the device.
  • The best way, which provides high quality random data but takes a long time (several minutes per gigabyte on most systems):
    dd if=/dev/urandom of=<device>
  • Fastest way, which provides lower quality random data:
    badblocks -c 10240 -s -w -t random -v <device>