fs(5) on OpenBSD
The text d38127a5523a, as OpenBSD 5.5, OpenBSD 5.4, OpenBSD 5.3, OpenBSD 5.2, OpenBSD 5.1, OpenBSD 5.0, OpenBSD 4.9, OpenBSD 4.8, OpenBSD 4.7, OpenBSD 4.6, OpenBSD 4.5, OpenBSD 4.4, OpenBSD 4.3, OpenBSD 4.2 shipped it.
format of file system volume