truncate -s 10G foo
fallocate -l 5G bar
It needs to be stated that truncate on a file system supporting sparse files will create a sparse file and fallocate will not
D. Hickok, D. Lesniak, und M. Rowe. 38th Midwest Instruction and Computing Symposium April 8 - 9, 2005. University of Wisconsin-Eau Claire, Eau Claire, WI, (2005)