Physical file systems are sometimes initialized in an address space called a colony address space. You can think of these address spaces as extensions of the kernel address space. The NFS Client and DFS Client physical file systems must be set up in a colony address space because they must use socket sessions to talk to their remote servers, which cannot be done from the kernel. You can choose to set up the TFS in a colony address space also; to make that decision see Running a temporary file system in a colony address space.

Some physical file systems cannot be initialized in colony address spaces; for example, the INET or CINET sockets file systems and HFS.