The SunOS release 5.7 mkfs command differs significantly from the SunOS release 4 version of the command. The SunOS release 5.7 version provides for different file system types, and its command syntax is entirely different (see "Generic File System Commands"). Like newfs, mkfs accepts only names conforming to the SunOS release 5.7 device naming conventions.
Although mkfs now supports different types of file systems, in practice it is almost always used to create ufs file systems. However, mkfs isn't usually run directly; it is usually called by the newfs command.
See mkfs(1) man pages for additional details.