CompTIA Linux+ XK0-006 (V8) Practice Question

The correct command is dd if=/dev/urandom of=/dev/sdb. This command reads pseudorandom data from the special device file /dev/urandom (the input file or if) and writes it directly to the target block device /dev/sdb (the output file or of), overwriting all existing data. Overwriting a drive with random data is a secure method to make the original data unrecoverable.

• dd if=/dev/zero of=/dev/sdb is incorrect because /dev/zero provides a continuous stream of null characters (zeros), not random data. While this does overwrite the data, it is considered less secure than using random data because the resulting pattern is uniform.
• dd if=/dev/sdb of=/dev/urandom is incorrect because it reverses the input and output, attempting to read the contents of the hard drive and write them to the /dev/urandom device, which is not the intended operation for wiping a drive.
• dd if=/dev/null of=/dev/sdb is incorrect because /dev/null is a special file that discards all data written to it and provides no data when read. Therefore, this command would write nothing to the drive.