Yukon Chang, Fall 1996 Operating System (II) Chapter 11 Supplement Slide 1 UNIX File System Layout u boot block contains bootstrap code that is read into the machine to boot the operating system u 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 u inode list is a list of inodes (explained later) u data blocks store file data and administrative data data blocksinode list super block boot block

Yukon Chang, Fall 1996 Operating System (II) Chapter 11 Supplement Slide 2 Inodes (Index Nodes) u 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 u see Fig on the textbook

Yukon Chang, Fall 1996 Operating System (II) Chapter 11 Supplement Slide 3 Directory Block u notably missing from inode information is the file name u file name is kept in a directory entry of directory block u the first two entries in a directory have names. and.. to inode 5foo.c3barmumble6 to inode to inode unused space

Yukon Chang, Fall 1996 Operating System (II) Chapter 11 Supplement Slide 4 Hard Links u an inode can be linked from many different directory entries, i.e., it may have many names to inode 5foo.c3barmumble6 inode 2714 reference count = 2

Yukon Chang, Fall 1996 Operating System (II) Chapter 11 Supplement Slide 5 Symbolic (Soft) Links u a symbolic link is a special file that contains a pathname. directories /usr/joe /usr/sue foo bar inodes file content /usr/joe/foo Hello, world