Minix file system

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The Minix file system is the file system of the former teaching operating system Minix .

history

Minix has been fully programmed as a Unix- like operating system by Andrew S. Tanenbaum as a teaching system since the 1980s (the current version is Minix 3.3 from 2014).

The Minix file system was designed for Minix. It is based on the basic structures of the Unix file system with the omission of complex functions in order to be able to structure the source code as clearly and simply as possible in the sense of the teaching use of Minix. It therefore has a number of limitations:

  • A partition cannot be larger than 64  MiB ( cluster addresses are represented as 16-bit integer numbers).
  • File names cannot be longer than 14 or 30 characters.
  • File links ("symbolic links", also "symlinks") cannot be used.

This file system was used as the standard by Linux until the introduction of the extended filesystem in April 1992 and was often used for (bootable) floppy disks , partly for RAM disks and in other areas of application because of the limited storage space required for administration.

construction

A Minix file system consists of six parts:

  • The boot sector , which is always located in the first block. It contains the boot loader that loads and starts the operating system when the computer starts.
  • The superblock that contains data about the file system. These data allow the respective operating system to localize and process further structures of the file system . Examples of the superblock's data are the number of inodes and clusters .
  • The inode bitmap is a simple representation of the status of all inodes. It is only shown whether an inode is occupied ("1") or free ("0").
  • The cluster bitmap has the same structure as the inode bitmap , but shows the status of the clusters in the data area .
  • The inodes area. Each file and each directory is represented by at least one inode, which in turn contains the following metadata :
  • Type (file, directory, device file or pipe )
  • User and group ID
  • Last change timestamp
  • Access permissions
  • size
  • Number of links
  • List of addresses that refer to the clusters in the data area in which the content data belonging to the inode is stored.
  • The data area is the part of the file system that naturally takes up the most space. The actual content of the files and directories is saved here.

(Note: In English-language texts, the cluster is usually referred to as a "zone" in relation to Minix.)

literature

  • Scott D. Heavner: Introduction to the Minix File System . 2000.
  • Andrew S. Tanenbaum, Albert S. Woodhull: Operating systems: design and implementation . 3rd edition, Prentice Hall, Upper Saddle River 1997, ISBN 0-13-142938-8 .