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UNIX File System Layout

UNIX File System Layout. boot block contains bootstrap code that is read into the machine to boot the operating system super block describes the state of a file system, how large it is, how many files it can store, where to find free space on the file system, etc

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UNIX File System Layout

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  1. UNIX File System Layout • boot block contains bootstrap code that is read into the machine to boot the operating system • super block describes the state of a file system, how large it is, how many files it can store, where to find free space on the file system, etc • inode list is a list of inodes (explained later) • data blocks store file data and administrative data boot block super block inode list data blocks

  2. Inodes (Index Nodes) • inodes exist in a statis form on disk, it consists of • file owner (individual owner and group owner) • file type (regular, directory, character/block device, ...) • access permission (r-xr-x---) • access and last modify time (of file and inode) • number of links to the file • pointers to data blocks • file size • see Fig. 11.7 on the textbook

  3. Directory Block • notably missing from inode information is the file name • file name is kept in a directory entry of directory block • the first two entries in a directory have names . and .. 5 foo.c 3 bar 6 mumble to inode to inode unused space to inode

  4. Hard Links • an inode can be linked from many different directory entries, i.e., it may have many names 5 foo.c 3 bar 6 mumble to inode inode 2714 reference count = 2

  5. Symbolic (Soft) Links • a symbolic link is a special file that contains a pathname. Hello, world /usr/joe foo /usr/sue /usr/joe/foo bar file content inodes directories

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