Add commands for creating large files

Author: Michael Kwardakov

README.md

@@ -280,6 +280,11 @@ mkdir empty && rsync -r --delete empty/ some-dir && rmdir some-dir
    setfacl --restore=permissions.txt
 ```
 
+- To create big dummy files really fast, use `truncate` (creates [sparse file](https://en.wikipedia.org/wiki/Sparse_file)) or
+  - `fallocate`: available for ext4, xfs, btrfs and ocfs2 filesystems
+  - `xfs_mkfile`: almost any filesystems, comes in xfsprogs package
+  - `mkfile`: is there for Unix-like systems like Solaris, Mac OS X etc
+
 ## System debugging
 
 - For web debugging, `curl` and `curl -I` are handy, or their `wget` equivalents, or the more modern [`httpie`](https://github.com/jkbrzt/httpie).