CompTIA Linux+ XK0-006 (V8) Practice Question

The correct command is dd if=/dev/zero of=report.log bs=1M count=1024.

• /dev/zero is a special character device that provides an infinite stream of null characters (0x00). Using it as the input file (if) for the dd command is the most efficient way to overwrite the target file (of=report.log) with null bytes as requested.

• Using /dev/null is incorrect because it is a special device, often called the 'bit bucket', that discards all data written to it. When used as an input source (if=/dev/null), it immediately returns an End-of-File (EOF), meaning no data would be written to report.log.

• Using /dev/random is also incorrect for this specific scenario. While it provides high-quality random data which can be used for secure wiping, the question specifies overwriting with 'null bytes' and emphasizes efficiency. /dev/random is much slower than /dev/zero because it can block waiting for the system to gather enough entropy (environmental noise) to generate true random numbers.

• Reversing the input and output files (if=report.log of=/dev/zero) is incorrect. This command would read the contents of report.log and pipe them to /dev/zero, where they would be discarded. The original report.log file would be read but not modified.