I wanted to do some testing of a cloud based next-gen firewall at work, and ideally I wanted to run a bunch of SSH/SCP file transfers to generate some traffic and log data.

Linux has the ‘dd’ command (Data Duplicator), which I have used in the past, but it is quite slow to create a large file:

dd if=/dev/zero of=./testfile.img bs=4k iflag=fullblock,count_bytes count=10G

I found the following ‘fallocate’ command, and it’s super quick to create a large file, much faster than ‘dd’. Fallocate is described as ‘Preallocate or deallocate space to a file’.

fallocate -l 10G gentoo_root.img

Thank you StackOverflow my friend, I found this nugget here.