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Ordinary files contain text, data, or executable programs.•Directoriesare binary files used to track other files and directories.•Special filesdo not contain data but instantiate for device I/O on UNIX systems.•Named pipesallow system processes to communicate with each other. The file’s function is to perform as a ‘pipe’ that transfers data between twoor more processes.•Linksare tools that are used to reference single files on a disk.•Symbolic linkscontain a pointer to another file. (LiveFire Labs, 2013) Inodes. The UNIX OS administers files with a control structure known as an inode (index node). The inode encompasses information on a particular file for the operating system’s use, which can include the inode number, access control list (ACL), file size, and much more. (Buse, 2013)File Allocation. In a UNIX system, a block and index system is the practice employed for file allocation. Part of the index is included in the file’s inode as a series of pointers; the first 12 pointers reference the first 12 blocks of a file. If there are more than twelve blocks in the file, then the 13thpointer references an indirect block, which consistsof pointers to the additional blocks. If the file involves more blocks, then the 14thpointer references a double indirect block, which in turn is comprised of pointers referencing single indirect blocks. If the file retains still more blocks, then the 15thpointer references a triple indirect block with pointers to more double indirect blocks. With this file allocation system, the maximum size of a file could be over 500GB. (Stallings, 2012, p. 556)
Directories. The organization of directories resembles a structure much like the branches on a tree. Each directory has files and/or other directories, known as subdirectories. (Stallings, 2012, p. 557) Volume structure. The UNIX filesystem as deployed on a single disk with this block structure:•Boot block. Contains the necessary code to boot the system.•Superblock. Contains necessary information about the file system, such as the sizes of partitions and inodes.•Inode table. Information on file inodes.•Data blocks. Information regarding the space available for storage of filesand directories.LinuxThe evolution of Linux began with the goal of creating a free, open source, alternative to UNIX. Although Linux and UNIX have a common foundation, Linux will run on a wider range of platforms than UNIX (Dougall, 2006).Virtual File System. What makes Linux so versatile and powerful is its use of a virtual file system (VFS), designed to support wide variety of file management systems and file structures. The VFS treats files as objects that share basic properties without regard to their target file system or their basic processes. In order to accomplish this goal,Linux uses a mapping module to transform the file system characteristics to the attributes needed by the VFS (Stallings, 2012, pp. 560-561).