CTFS 

CTFS (the contract file system) is the interface for creating, controlling, and observing contracts. A contract enhances the relationship between a process and the system resources it depends on by providing richer error reporting and (optionally) a means of delaying the removal of a resource.

The service management facility (SMF) uses process contracts (a type of contract) to track the processes which compose a service, so that a failure in a part of a multi-process service can be identified as a failure of that service. 

FIFOFS (first-in first-out) 

Named pipe files that give processes common access to data

FDFS (file descriptors) 

Provides explicit names for opening files by using file descriptors

MNTFS 

Provides read-only access to the table of mounted file systems for the local system 

NAMEFS 

Used mostly by STREAMS for dynamic mounts of file descriptors on top of files

OBJFS 

The OBJFS (object) file system describes the state of all modules currently loaded by the kernel. This file system is used by debuggers to access information about kernel symbols without having to access the kernel directly.

SHAREFS 

Provides read-only access to the table of shared file systems for the local system

SPECFS (special) 

Provides access to character special devices and block devices

SWAPFS 

Used by the kernel for swapping