MINIX file system

Minix file system
Developer(s)	Open Source Community
Full name	MINIX file system version 3
Introduced	1987;37 years ago with Minix 1.0
Partition IDs	0x81 (MBR)
Features
Dates recorded	last metadata change, last file change, last file access
Date resolution	1s
File system; permissions	POSIX
Transparent; compression	No
Transparent; encryption	No (provided at the block device level)
Other
Supported; operating systems	Minix 3, Linux, MiNT and HelenOS

Last updated March 30, 2024

The Minix file system is the native file system of the Minix operating system. It was written from scratch by Andrew S. Tanenbaum in the 1980s and aimed to replicate the structure of the Unix File System while omitting complex features, and was intended to be a teaching aid. It largely fell out of favour among Linux users by 1994 due to the popularity of other filesystems - most notably ext2 - and its lack of features, including limited partition sizes and filename length limits.

History

MINIX was written from scratch by Andrew S. Tanenbaum in the 1980s, as a Unix-like operating system whose source code could be used freely in education. The MINIX file system was designed for use with MINIX; it copies the basic structure of the Unix File System but avoids any complex features in the interest of keeping the source code clean, clear and simple, to meet the overall goal of MINIX to be a useful teaching aid.^[1]

When Linus Torvalds first started writing his Linux operating system kernel (1991), he was working on a machine running MINIX, and adopted its file system layout. This soon proved problematic, since MINIX restricted filename lengths to 14 characters (30 in later versions), it limited partitions to 64 megabytes,^[2] and the file system was designed for teaching purposes, not performance.^[3] The Linux implementation of the MINIX fs was multi-threaded, whereas the MINIX implementation of the fs was single-threaded.^[4] The extended file system (ext; April 1992) was developed to replace MINIX's, but it was only with the second version of this, ext2, that Linux obtained a commercial-grade file system.^[3] As of 1994, the MINIX file system was "scarcely in use" among Linux users.^[2]

Design and implementation

A MINIX file system has six components:^[1]

The Boot Block which is always stored in the first block. It contains the boot loader that loads and runs an operating system at system startup.
The second block is the Superblock which stores data about the file system, that allows the operating system to locate and understand other file system structures. For example, the number of inodes and zones, the size of the two bitmaps and the starting block of the data area.
The inode bitmap is a simple map of the inodes that tracks which ones are in use and which ones are free by representing them as either a one (in use) or a zero (free).
The zone bitmap works in the same way as the inode bitmap, except it tracks the zones.
The inodes area. Each file or directory is represented as an inode, which records metadata including type (file, directory, block, char, pipe), IDs for user and group, three timestamps that record the date and time of last access, last modification and last status change. An inode also contains a list of addresses that point to the zones in the data area where the file or directory data is actually stored.
The data area is the largest component of the file system, using the majority of the space. It is where the actual file and directory data are stored.

Related Research Articles

XFS is a high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; as of June 2014, XFS is supported by most Linux distributions; Red Hat Enterprise Linux uses it as its default file system.

ReiserFS is a general-purpose, journaling file system initially designed and implemented by a team at Namesys led by Hans Reiser and licensed under GPLv2. Introduced in version 2.4.1 of the Linux kernel, it was the first journaling file system to be included in the standard kernel. ReiserFS was the default file system in Novell's SUSE Linux Enterprise until Novell decided to move to ext3 for future releases on October 12, 2006.

ext2, or second extended file system, is a file system for the Linux kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been designed according to the same principles as the Berkeley Fast File System from BSD, it was the first commercial-grade filesystem for Linux.

ext3, or third extended filesystem, is a journaled file system that is commonly used by the Linux kernel. It used to be the default file system for many popular Linux distributions. Stephen Tweedie first revealed that he was working on extending ext2 in Journaling the Linux ext2fs Filesystem in a 1998 paper, and later in a February 1999 kernel mailing list posting. The filesystem was merged with the mainline Linux kernel in November 2001 from 2.4.15 onward. Its main advantage over ext2 is journaling, which improves reliability and eliminates the need to check the file system after an unclean shutdown. Its successor is ext4.

Linux has several filesystem drivers for the File Allocation Table (FAT) filesystem format. These are commonly known by the names used in the mount command to invoke particular drivers in the kernel: msdos, vfat, and umsdos.

The Unix file system (UFS) is a family of file systems supported by many Unix and Unix-like operating systems. It is a distant descendant of the original filesystem used by Version 7 Unix.

The inode is a data structure in a Unix-style file system that describes a file-system object such as a file or a directory. Each inode stores the attributes and disk block locations of the object's data. File-system object attributes may include metadata, as well as owner and permission data.

HFS Plus or HFS+ is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the Apple File System (APFS), released with macOS High Sierra in 2017. HFS+ is also one of the formats supported by the iPod digital music player.

The extended file system, or ext, was implemented in April 1992 as the first file system created specifically for the Linux kernel. It has metadata structure inspired by traditional Unix filesystem principles, and was designed by Rémy Card to overcome certain limitations of the MINIX file system. It was the first implementation that used the virtual file system (VFS), for which support was added in the Linux kernel in version 0.96c, and it could handle file systems up to 2 gigabytes (GB) in size.

In computing, a file system or filesystem governs file organization and access. A local file system is a capability of an operating system that services the applications running on the same computer. A distributed file system is a protocol that provides file access between networked computers.

Filesystem in Userspace (FUSE) is a software interface for Unix and Unix-like computer operating systems that lets non-privileged users create their own file systems without editing kernel code. This is achieved by running file system code in user space while the FUSE module provides only a bridge to the actual kernel interfaces.

A file system API is an application programming interface through which a utility or user program requests services of a file system. An operating system may provide abstractions for accessing different file systems transparently.

Extended file attributes are file system features that enable users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem. Unlike forks, which can usually be as large as the maximum file size, extended attributes are usually limited in size to a value significantly smaller than the maximum file size. Typical uses include storing the author of a document, the character encoding of a plain-text document, or a checksum, cryptographic hash or digital certificate, and discretionary access control information.

The following tables compare general and technical information for a number of file systems.

ext4 is a journaling file system for Linux, developed as the successor to ext3.

dm-crypt is a transparent block device encryption subsystem in Linux kernel versions 2.6 and later and in DragonFly BSD. It is part of the device mapper (dm) infrastructure, and uses cryptographic routines from the kernel's Crypto API. Unlike its predecessor cryptoloop, dm-crypt was designed to support advanced modes of operation, such as XTS, LRW and ESSIV, in order to avoid watermarking attacks. In addition to that, dm-crypt addresses some reliability problems of cryptoloop.

Btrfs is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager, developed together. It was founded by Chris Mason in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel.

In computer operating systems, mkfs is a command used to format a block storage device with a specific file system. The command is part of Unix and Unix-like operating systems. In Unix, a block storage device must be formatted with a file system before it can be mounted and accessed through the operating system's filesystem hierarchy.

An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a high fanout factor, use a hash of the filename, and do not require balancing. The HTree algorithm is distinguished from standard B-tree methods by its treatment of hash collisions, which may overflow across multiple leaf and index blocks. HTree indexes are used in the ext3 and ext4 Linux filesystems, and were incorporated into the Linux kernel around 2.5.40. HTree indexing improved the scalability of Linux ext2 based filesystems from a practical limit of a few thousand files, into the range of tens of millions of files per directory.

References

1 2 Tanenbaum, Andrew S; Albert S. Woodhull (14 January 2006). Operating Systems: Design and Implementation (3rd ed.). Prentice Hall. ISBN 0-13-142938-8.
1 2 Strobel, Stefan; Uhl, Thomas (1994). Linux—Unleashing the Workstation in Your PC. Springer-Verlag. p. 54.
1 2 Mauerer, Wolfgang (2010). Professional Linux Kernel Architecture. John Wiley & Sons. ISBN 9781118079911.
↑ "linux release 0.01 - refs/tags/v0.01 - pub/scm/linux/kernel/git/nico/archive - Git at Google". kernel.googlesource.com. Retrieved 2024-03-29.

External links

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[TanenbaumOSBook-1] 1 2 Tanenbaum, Andrew S; Albert S. Woodhull (14 January 2006). Operating Systems: Design and Implementation (3rd ed.). Prentice Hall. ISBN 0-13-142938-8.

[Strobel-2] 1 2 Strobel, Stefan; Uhl, Thomas (1994). Linux—Unleashing the Workstation in Your PC. Springer-Verlag. p. 54.

[Mauerer-3] 1 2 Mauerer, Wolfgang (2010). Professional Linux Kernel Architecture. John Wiley & Sons. ISBN 9781118079911.

[4] "linux release 0.01 - refs/tags/v0.01 - pub/scm/linux/kernel/git/nico/archive - Git at Google". kernel.googlesource.com. Retrieved 2024-03-29.

[1]

[2]

[3]

[4]