SysV
From FreeBSDwiki
System V release of the AT&T Unix originally created by Dennis Richie and Ken Thompson. Sometimes referred to as SRV. After V, they stopped changing the system number and started versioning the V release; the last release was System V Release 7. Linux is an example of a SysV-based Unix. See also BSD and this excellent article by Dru Lavigne at ONLamp for more information on differences between SysV and BSD systems.