Give an overview of UNIX based file systems.

UNIX and UNIX-like operating systems allocate a device name to each device, other than this isn't how the files on that device are accessed. in its place UNIX creates a virtual file system which makes all the files on all the devices appear to exist under the one hierarchy. This means, in UNIX there is one root directory and every file existing on the system is located under it somewhere. Additionally, the UNIX root directory doesn't have to be in any physical place. It mightn't be on your first hard drive - it mightn't even be on your computer. UNIX is able to use a network shared resource as its root directory.

To gain access to files on one more device you must first inform the operating system where in the directory tree you would like those files to appear. This process is called as mounting a file system. For instance to access the files on a CD-ROM, casually, one ought to tell the operating system "Take the file system from this CD-ROM and make it appear under the directory /mnt". The directory specified to the operating system is called as the mount point - in this case it is /mnt. The /mnt directory exist on all Unix systems as a specified in the Filesystem Hierarchy Standard and is intended specifically for use as a mount point for temporary media like floppy disks or CDs. It perhaps empty or it may contain subdirectories for mounting individual devices. Usually, only the administrator (that is root user) may authorize the mounting of file systems.

Unix-like operating systems habitually include software and tools that assist in the mounting process and provide it new functionality. A few of these strategies have been coined "auto-mounting" as a reflection of their purpose.

• In many circumstances, file systems additional than the root need to be available as soon as the operating system has booted. All Unix-like systems thus provide a facility for mounting filesystems at boot time. System administrators define these file systems in the configuration file fstab, which as well indicates options and mount points.

• In few situations, there is no requiring mounting certain filesystems at boot time, though their use may be desired thereafter. There are a few utilities for Unix-like systems that permit the mounting of predefined filesystems upon demand.

• Detachable media have become very common with microcomputer platforms. They permit programs and data to be transferred between machines without a physical connection. Two common instance include CD-ROMs and DVDs. Utilities have thus been developed to detect the presence and availability of a medium and after that mount that medium without any user intervention.

• Progressive Unix-like systems have as well introduced a concept called super mounting. For instance, a floppy disk that has been super mounted is able to be physically removed from the system. Under normal conditions, the disk must have been synchronized and after that unmounted before its removal. Provided synchronization has take place, a different disk is able to be inserted into the drive. The system automatically observes that the disk has changed and updates the mount point contents to reflect the new medium.