Preallocate a large file with fallocate
A way to fill up lots of disk space
Usage:
fallocate -l <size> </path/to/file>
For example, to allocate 50G of space to ~/largefile:
fallocate -l 50G ~/largefile
Reference
https://unix.stackexchange.com/questions/292843/way-to-instantly-fill-up-use-up-lots-of-disk-space