UNIX also features a hierarchical file system that makes it easy for you to separate related files logically into directories, which are themselves special files. While MS-DOS and similar operating systems feature a hierarchical file system with simple file access permissions (such as read only), UNIX has a complete user-based file access permission system. Like process management, each file on the system is “owned” by a specific user, and by default only that user can perform operations on that file. Privileged users can perform all operations on all files on the file system. Interestingly, a special file permission allows unprivileged users to execute certain commands and applications with superuser privileges (such as setuid).
The following file system types are supported by the kernel:
cachefs The CacheFS cached file system
hsfs The High Sierra file system
nfs The Network File System (NFS)
pcfs The MS-DOS file system
tmpfs A file system that uses memory
ufs The standard UNIX File System (UFS)
The default local file system type is contained in the /etc/default/fs file, while the default remote file system type is contained in the /etc/default/fstypes file.