file systems

• file system or filesystem (FS or fs)

• file

• filename

• structures:

  • byte sequence
  • record sequence
  • tree

• file types:

  • regular
    • ASCII file vs binary file
    • executable vs non-executable file
  • directory
  • character special file (in UNIX, they are in /dev/)
  • block special files (in UNIX, they are in /dev/)

• memory-mapped file

• archive

  • header
    • module name
    • date
    • owner
    • protection
    • size
  • object module

• executable binary file

• file access

  • random access (or direct access)
  • sequential access

• File attributes

• contiguous allocation

• linked list allocation

  • linked list allocation using an index

• indexed allocation

• a directory is a special file that contains directory entries

  • a directory entry is a pair of $⟨\text{filename, inode-number}⟩$
  • inode (index node)
    • contains:
      • file type
      • file size
    • (Addresses per indirect block)
      • $\text{Max-file-size}=\left(\text{direct-block-addresses}+\frac{\text{block-size}}{\text{disk-address-size}}\right)\times \text{block-size}$
    • Indirect block

• hard link

• symbolic link (or symlink or soft link)

• disk quota

• block cache (buffer cache)

  • write policies
    • write-through
    • non write-through