UNIX File Management

What are the three types of file types

• Directories

• Special files

• Ordinary files

Unix disk organization

• 512 bytes of blocks organized into four basic regions

  • First region (address 0): reserved for booting

  • Second region: contains disk size and other regions’ boundaries

  • Third region includes: list of file definitions called the “i-list”, which is a list of file descriptors (called “i-nodes”), one for each file. The position of an i-node is called an “i-number” and this uniquely identifies a file.

  • Remaining region: free blocks available for file storage

I-node info

• an entry in i-list

  • contains 13 disk addresses

• Contains specific file info

  • owner’s identification

  • protection bits, physical address, file size

  • time of creation, last, use + last update

  • num of links

  • file type

    • directory, ordinary, special

UNIX file naming conventions

• case-sensitive filenames

• 255 character length

• hierarchal tree file structure

• / = root

  • /programs/pay/checks (for checks file)

• .. = moves you up the path name

UNIX directory listings

• access control

• num of links

• group

• owner

• num of bytes

• date created

• time created

• filename

Links

• created when a file is made

• when a shared file is deleted, it decreases by one

• it reaches 0 when the file is deleted, and all disks are deallocated