Plan 9 from Bell Labs

From Wikipedia, the free encyclopedia
  (Redirected from Plan 9 (operating system))
Jump to: navigation, search
Plan 9 from Bell Labs
Glenda, the Plan 9 Bunny
Plan 9 from Bell Labs (Installation).png
Installation of Plan 9
Company / developer Bell Labs
Programmed in Dialect of ANSI C
Working state Current
Source model Free and open source software
Initial release 1992 (universities) / 1995 (general public)
Latest stable release Fourth Edition / 28 April 2002 (2002-04-28)
Latest unstable release Snapshots / daily
Available language(s) English
Update method replica
Supported platforms x86 / Vx32, x86-64, MIPS, DEC Alpha, SPARC, PowerPC, ARM
Default user interface rio / rc
License Lucent Public License
Official website plan9.bell-labs.com/plan9

Plan 9 from Bell Labs is a free software distributed operating system. It was developed primarily for research purposes as the successor to Unix by the Computing Sciences Research Center at Bell Labs between the mid-1980s and 2002. Plan 9 continues to be used and developed by operating system researchers and hobbyists.[1][2]

Along with its strict "everything is a file" Unix philosophy concept, Plan 9 is known for its novel features such as uniform medium-agnostic access to the local and remote resources with a 9P protocol, union mounts, improved proc file system and native unicode support throughout the system. In Plan 9 all system interfaces, including those required for networking and the user interface, are represented through the file system rather than specialized interfaces, thus allowing system administrators to build single system image clusters by using basic tools such as mount.

The name Plan 9 from Bell Labs is a reference to the Ed Wood 1959 cult science fiction Z-movie Plan 9 from Outer Space.[3] Another reference to Wood's legacy is the name of the Plan 9's mascot—Glenda, the Plan 9 Bunny.[4]

Contents

[edit] History

Plan 9 was a Bell Labs internal project from its start during the mid 1980s. It replaced Unix as Bell Labs' primary platform for research. It explored several changes to the original Unix model that facilitate the use and programming of the system, notably in distributed multi-user environments. In 1992, Bell Labs provided the first public release to universities, and three years later a commercial second release version became available to the general public. In the late 1990s, Lucent Technologies, having inherited Bell Labs, dropped commercial support for the project. In 2000, a non-commercial third release was distributed under an open source license. A fourth release under a new free software license occurred in 2002.[5]

A user and development community, including current and former Bell Labs members and Massachusetts Institute of Technology personnel, continues to produce minor daily releases in form of ISO images. Bell Labs still hosts the development.[6] The development source tree is accessible over the 9P and HTTP protocols and is used to update existing installations.[7] In addition to the official components of the OS included in the ISOs, Bell Labs also hosts a repository of externally developed applications and tools.

Plan 9 from Bell Labs was originally developed by members of the Computing Science Research Center at Bell Labs, the same group that originally developed UNIX and C.[8] The Plan 9 team was initially led by Rob Pike, Ken Thompson, Dave Presotto and Phil Winterbottom, with support from Dennis Ritchie as head of the Computing Techniques Research Department. Over the years many notable developers have contributed to the project including Brian Kernighan, Tom Duff, Doug McIlroy, Bjarne Stroustrup and Bruce Ellis.[9]

[edit] Design concepts

Plan 9 from Bell Labs is like the Quakers: distinguished by its stress on the 'Inner Light,' noted for simplicity of life, in particular for plainness of speech. Like the Quakers, Plan 9 does not proselytize.

—Sape J. Mullender, Pierre G. Janson.
Real Time in Real Operating System[10]

Plan 9 is an evolution of UNIX design concepts:[11]

  1. all objects are either files or file systems
  2. communication is over a network
  3. private namespaces allow their owners to access local and remote processes transparently

Plan9 is a grid computing platform. It is an effort to provide a computing environment for geographically distributed clusters running on heterogeneous hardware, engineered for modern distributed environments and designed from the start to be a networked operating system.[12] It can be installed and used on a single self-contained system, but also has the capability to separate the functional components of the OS between separate hardware platforms. In a typical Plan 9 installation, users work at lightweight terminals running the rio GUI, and they connect to a network to gain access to CPU servers which handle computation-intensive processes. Permanent data storage is provided by additional network hosts acting as file servers and archival storage.[13] Currently available desktop computers can emulate this architecture internally using multiple virtual machines.

[edit] 9P protocol

Main article: 9P

To reduce the number of custom APIs and system calls, Plan 9 makes heavy use of universal 9P protocol. 9p is generic medium-agnostic byte-oriented protocol that provides for messages delivered between the server and the client.[14]

The typical Plan 9 application is a file server, accessible by 9P regardless of the application's nature.[10] Thus the protocol is used to refer to and communicate with processes, programs, and data, including both the user interface and the network.[15] With the release of the 4th edition, it was modified and renamed 9P2000.[5]

Unlike most other operating systems Plan9 does not provide special application programming interfaces (such as Berkeley sockets, X resources or ioctl system calls) to access the devices.[14] Instead, Plan9 device drivers implement the control interfaces as file system hierarchies, so that the hardware functionality can be accessed by the ordinary file input/output operations read and write. Consequently, sharing the device across the network can be accomplished regardless of a driver's networking capabilities by mounting the corresponding directory tree to the target machine.[3]

[edit] Union directories and namespaces

Plan9 allows the user to collect the files, called names, from different directory trees in a single location. The name resolution is then performed from top to bottom: if the name doesn't exist in the top directory, it is looked up in lower ones until found. The same name in lower directories will be shown in the directory listing, but will not be accessible, thus the merging of subdirectories is not handled.[16]

A union directory can be created by using the bind command. In the following example, /home/val/bin would be union mounted after /bin, as requested by option -a:

; bind -a /home/val/bin /bin

In this example, if the name cannot be found in the contents of /bin directory, it will be looked up in /home/val/bin.

This mechanism of union directories replaces the search path of conventional UNIX shells. As far as you are concerned, all executable programs are in /bin.

—Brian Kernighan[17]

Furthermore, the systems keeps separate mount tables for each process,[10] thus providing every application with a view of the system as a single, coherent namespace that appears as a hierarchical file system but may represent local or remote (physically separated over the network) resources. The namespace of each process can be constructed independently, and the user may work simultaneously with applications that have heterogeneous namespaces.[18] The namespaces may be used to create an isolated environment similar to chroot in a more secure way.[14]

Plan 9's union directory architecture inspired BSD and Linux union file systems implementations.[19]

[edit] Special virtual filesystems

[edit] /proc

Listing processes with list contents of directory (ls, lc) command[20] in /proc
Main article: procfs

Instead of requiring special software for process management, Plan 9 provides a file system hierarchy of running processes under the /proc directory. Each process appears as a named object—a directory with information and control files—which can be manipulated by the ordinary means of input/output.[16]

The file system approach to the process management allows Plan 9 users to manage processes with file management tools such as ls and cat; however, the processes cannot be copied and moved as files.[21]

[edit] /net

Plan 9 does not have system calls for the multitude of communication protocols or device driver interfaces; instead the /net file server is used as the API for all TCP/IP traffic. This allows users to establish, manage, use and close network connections by reading or writing data to control files (even with scripts or shell tools). Relevant sub-directories such as /net/tcp and /net/udp are used as an interface to respective protocols.[21]

[edit] Unicode

Further information: UTF-8, Comparison of Unicode encodings

To reduce the complexity of managing character encodings, Plan 9 uses Unicode throughout the system. The initial Unicode implementation was ISO 10646. Ken Thompson invented UTF-8, which became the native encoding in Plan 9. The entire system was converted to general use in 1992.[22] UTF-8 preserves backward compatibility with traditional null terminated strings enabling more reliable information processing and the chaining of multilingual string data with Unix pipes between multiple processes. Using a single UTF-8 encoding—with characters for all cultures and regions—eliminates the need in switching between code sets.[23]

[edit] Combining the design concepts

Though interesting on their own, the design concepts of Plan 9 were supposed to be most useful when combined together. For example, to implement network address translation (NAT) server one can simply create a union directory overlaying the router's /net directory tree with its own /net. Similarly one can implement a virtual private network (VPN) by overlaying in a union directory a /net hierarchy from a remote gateway, using secured 9P over the public Internet. Union directory with /net hierarchy and filters can be used to sandbox an untrusted application or to implement a firewall.[14] In the same manner, the distributed computing network can be composed with union directory of /proc hierarchies from remote hosts, which allows interacting with them as if they are local.

Combining these methods one can assemble a complex distributed computing environment with user terminals, file servers that store permanent data, and other servers that provide additional processors, user authentication, and network gateways, all reusing the existing hierarchical name system.[21]

[edit] Software for Plan 9

Further information: list of Plan 9 applications

The distribution package for Plan 9 includes special compiler variants and programing languages, and provides a tailored set of libraries along with a windowing user interface system specific to Plan 9.[24] Its compiler is a dialect of C with some extensions and restrictions.[25]

As a benefit from the system's design, most tasks in Plan 9 can be accomplished by using ls, cat, grep, cp and rm utilities in combination with the rc shell (the default Plan 9 shell).

Factotum is an authentication and key management server for Plan 9. It handles authentication on behalf of other programs such that both secret keys and implementation details need only be known to Factotum.[26]

[edit] The use of graphical capabilities

Plan 9 running acme and terminal emulator

Plan 9 was initially designed to make use of a windowing system; this differentiates it from Unix-like operating systems.[15] When used with a supported video card, Plan 9 will by default boot into the rio windowing system in which the user can create new windows with a terminal emulator running rc.[27] Graphical applications invoked from this shell replace it in its window.

The plumber utility provides the user with an inter-process communication (IPC) mechanism which allows the passing of resources to the default applications in a way similar to the action of double-clicking on file objects in most graphical file managers of modern systems.

For text editing, the standard installation of Plan 9 provides the sam (simpler) and acme (more advanced) text editors.[28]

[edit] Storage system

Plan 9 supports FAT and Fossil file systems. The latter was designed at Bell Labs specifically for Plan 9 and provides snapshot storage capability. It can be used directly with a hard drive or backed with Venti—an archival file system and permanent data storage system.

[edit] UNIX compatibility

Though Plan 9 was supposed to be a further development of UNIX concepts, compatibility with preexisting UNIX software was never the goal for the project. Still, many command line utilities of Plan 9 have aliases to the names of their UNIX counterparts.[20]

Plan 9 can support POSIX applications and can emulate the Berkeley socket interface through the ANSI/POSIX Environment (APE).[29] Some Linux binaries can be used with the help of a "linuxemu" (Linux emulator) application; however, it is still a work in progress.[30]

[edit] Impact

wmii X window manager is designed after acme text editor for Plan 9[31]

Plan 9 demonstrated that a central concept of Unix—that every system interface could be represented as sets of files—could be successfully implemented in a modern distributed system.[27] Some features from Plan 9, like the UTF-8 character encoding of Unicode, have been implemented in other operating systems. Unix-like operating systems such as Linux have implemented 9P, Plan 9's file system and limited forms of rfork-like system calls. Additionally, in Plan 9 from User Space, several of Plan 9's applications and tools, including the rc shell, have been ported to Unix and Linux systems and have achieved some level of popularity. Several projects seek to replace the GNU operating system programs surrounding the Linux kernel with the Plan 9 operating system programs.[32][33] 9wm window manager is designed after 8½, the older windowing system of Plan 9;[34] wmii is also heavily influenced by Plan 9.[31]

However, Plan 9 has never approached Unix in popularity, and was primarily a research tool:

Plan 9 failed simply because it fell short of being a compelling enough improvement on Unix to displace its ancestor. Compared to Plan 9, Unix creaks and clanks and has obvious rust spots, but it gets the job done well enough to hold its position. There is a lesson here for ambitious system architects: the most dangerous enemy of a better solution is an existing codebase that is just good enough.
—Eric S. Raymond[3]

Other criticisms focused on the lack of commercial backup, the low number of end user applications, and the device drivers.[27][28]

Plan 9 proponents and developers claim that the problems hindering its adoption have been solved, that its original goals as a distributed system, development environment, and research platform have been met, and that it enjoys moderate but growing popularity.[10] Inferno, through its hosted capabilities, has been a vehicle to bring Plan 9 technologies to other systems as a hosted part of heterogeneous computing grids.[35][36][37][38]

Several projects actively work to extend Plan 9, including 9atom and Plan 9 from The People's Front of Cat-v.org (plan9front). These forks augment Plan 9 with additional hardware drivers and software including nupas (improved Upas e-mail file system), go compiler, Mercurial version control system support, and other programs.[2][39]

[edit] License

The full source code is freely available under Lucent Public License 1.02, and considered to be open source by the Open Source Initiative (OSI), and free software by the Free Software Foundation. It passes the Debian Free Software Guidelines.[14] However, it is incompatible with the GNU General Public License.[40]

[edit] See also

Portal icon Free software portal

[edit] References

  1. ^ "Plan 9 Forked, Continues as 9front". OSNews. 2011-07-16. http://www.osnews.com/story/15235/Investigating_the_Plan_9_Operating_System. Retrieved 2011-12-31. 
  2. ^ a b "9atom". http://www.quanstro.net/plan9/9atom/index.html. Retrieved 2011-11-11. 
  3. ^ a b c Raymond, Eric S. (2003-09-17). "Plan 9: The Way the Future Was". The Art of UNIX Programming. Addison-Wesley. ISBN 0-13-142901-9. http://catb.org/~esr/writings/taoup/html/plan9.html. Retrieved 2007-05-07. 
  4. ^ "Glenda, the Plan 9 Bunny". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/plan9/glenda.html. Retrieved 2012-01-26. 
  5. ^ a b Loli-Queru, Eugenia (2002-04-29). "Bell Labs Releases New Version of Plan 9". OSNews. http://www.osnews.com/story/1001/Bell_Labs_Releases_New_Version_of_Plan_9. Retrieved 2011-12-31. 
  6. ^ "How to contribute". Bell Labs. Lucent Technologies. http://www.plan9.bell-labs.com/wiki/plan9/How_to_contribute/index.html. Retrieved 2011-11-30. 
  7. ^ "Staying up to date". Bell Labs. Lucent Technologies. http://cm.bell-labs.com/wiki/plan9/Staying_up_to_date/index.html. Retrieved 2006-04-27. 
  8. ^ "From the inventors of UNIX system comes Plan 9 from Bell Labs" (Press release). Lucent Technologies. 1995-07-18. Archived from the original on 2006-02-09. http://web.archive.org/web/20060209203907/http://www.lucent.com/press/0795/950718.bla.html. 
  9. ^ McIlroy, Doug (1995-03). "Preface to the Second (1995) Edition". Bell Labs. Lucent Technologies. http://cm.bell-labs.com/sys/man/preface.html. Retrieved 2006-04-02. 
  10. ^ a b c d Mullender, Sape J.; Janson, Pierre G. (2004-02-26). "Real Time in Real Operating System". In Herbert, Andrew J.; Jones, Karen Spärck. Computer systems: theory, technology, and applications : a tribute to Roger Needham. Springer Science+Business Media. p. 211. ISBN 978-0-387-20170-2. http://books.google.com/books?id=O897whP-DYAC&pg=PA211. Retrieved 2011-12-24. 
  11. ^ Bischof, Hans-Peter; Imeyer, Gunter; Wellhöfer, Bernhard & Schreiner, Axel-Tobias (1999). Das Netzbetriebssystem Plan 9. ISBN 3-446-18881-9. 
  12. ^ Hancock, Brian (2003). "Reinventing Unix: an introduction to the Plan 9 operating system". Library Hi Tech (MCB UP) 21 (4): 471–476. doi:10.1108/07378830310509772. 
  13. ^ Presotto, Dave; Pike, Rob; Thompson, Ken; Trickey, Howard. "Plan 9, A Distributed System" (PDF). Bell Labs. Lucent Technologies. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.41.9192&rep=rep1&type=pdf. Retrieved 2011-01-03. 
  14. ^ a b c d e Pereira, Uriel M. (2006) (avi). The Unix Spirit set Free: Plan 9 from Bell Labs. FOSDEM. http://ftp.belnet.be/mirror/FOSDEM/2006/FOSDEM2006-plan9.avi. Retrieved 2011-12-02. Lay summary. 
  15. ^ a b Minnich, Ron (2005). "Why Plan 9 is not dead yet And What we can learn from it" (pdf). Los Alamos National Laboratory. FAST-OS. http://www.cs.unm.edu/~fastos/05meeting/PLAN9NOTDEADYET.pdf. Retrieved 2011-12-02. 
  16. ^ a b Ballesteros, Francisco J. (2007-09-28). "Introduction to OS abstractions using Plan 9 from Bell Labs" (pdf). Universidad Rey Juan Carlos. Archived from the original on 2010-09-21. http://web.archive.org/web/20100922172010/http://plan9.escet.urjc.es/who/nemo/9.intro.pdf. 
  17. ^ Kernighan, Brian (1995). "Readme". Lucent Technologies. http://mirtchovski.com/p9/README.html. Retrieved 2012-01-25.  Hosted by mirtchovski.com.
  18. ^ Pike, R.; Presotto, D.; Thompson, K.; Trickey, H.; Winterbottom, P.. "The Use of Name Spaces in Plan 9". Bell Labs. cat-v.org. http://doc.cat-v.org/plan_9/4th_edition/papers/names. Retrieved 2011-12-05. 
  19. ^ Valerie, Aurora (2009-03-25). "Union file systems: Implementations, part I". LWN.net. http://lwn.net/Articles/325369/. Retrieved 2011-12-05. 
  20. ^ a b "UNIX to Plan 9 command translation". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/wiki/plan9/UNIX_to_Plan_9_command_translation/index.html. Retrieved 2011-12-02. 
  21. ^ a b c Pike, R.; Presotto, D.; Dorward, S.; Flandrena, B.; Thompson, K.; Trickey, H.; Winterbottom, P.. "Plan 9 from Bell Labs". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/sys/doc/9.html. Retrieved 2011-12-02. 
  22. ^ Pike, Rob (2003-04-30). "UTF-8 History". http://www.cl.cam.ac.uk/~mgk25/ucs/utf-8-history.txt. Retrieved 2006-04-27. 
  23. ^ Lunde, Ken (1999-01). CJKV information processing. O'Reilly Media. p. 466. ISBN 978-1-56592-224-2. http://books.google.com/books?id=Cn7jnk9WwZEC&pg=PA466. Retrieved 2011-12-23. 
  24. ^ Dixon, Rod (2004). Open source software law. Artech House. p. 213. ISBN 978-1-58053-719-3. http://books.google.com/books?id=9b_vVPf53xcC&pg=PA213. Retrieved 2011-12-25. 
  25. ^ Thompson, Ken (1992-02). "A new C Compiler". Australian UNIX systems User Group Newsletter (Kensington, Australia: AUUG, Inc.) 13 (1): 31–41. ISSN 1035-7521. http://books.google.com/books?id=OdMJUPKY2LcC&pg=PA31. Retrieved 2011-12-25. 
  26. ^ Cox, R.; Grosse, E.; Pike, R.; Presotto, D.; Quinlan, S.. "Security in Plan 9". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/sys/doc/auth.html. Retrieved 2011-12-02. 
  27. ^ a b c Hudson, Andrew (2006-07-19). "Investigating the Plan 9 Operating System". OSNews. http://www.osnews.com/story/15235/Investigating_the_Plan_9_Operating_System. Retrieved 2011-12-31. 
  28. ^ a b "An interview with Russ Cox". The Setup. 2011-04-09. http://russ.cox.usesthis.com/. Retrieved 2012-01-01. 
  29. ^ Trickey, Howard. "APE – The ANSI/POSIX Environment". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/sys/doc/ape.html. Retrieved 2011-04-27. 
  30. ^ "Linux emulation". Bell Labs. Lucent Technologies. http://plan9.bell-labs.com/wiki/plan9/Linux_emulation/index.html. Retrieved 2011-12-02. 
  31. ^ a b "window manager improved 2". suckless.org. http://wmii.suckless.org/. Retrieved 2012-01-02. "[wmii] has a 9p filesystem interface and supports classic and tiling (acme-like) window management." 
  32. ^ "Glendix: Bringing the beauty of Plan 9 to Linux". http://www.glendix.org/. Retrieved 2011-12-01. 
  33. ^ "Plan 9 From Gentoo: Plan 9 Meets Gentoo". Gentoo Linux. http://soc.dev.gentoo.org/~rps/plan9/. Retrieved 2011-12-01. 
  34. ^ "The 9wm Window Manager". 9wm. http://unauthorised.org/dhog/9wm.html. Retrieved 2012-01-02. "9wm is an X window manager which attempts to emulate the Plan 9 window manager 8-1/2 as far as possible within the constraints imposed by X." 
  35. ^ "9grid". Bell Labs. Lucent Technologies. http://cm.bell-labs.com/wiki/plan9/9grid/. Retrieved 2006-03-28. 
  36. ^ "Press Release: Vita Nuova Supplies Inferno Grid to Evotec OAI" (pdf) (Press release). Vita Nuova. 2004-05-18. http://www.vitanuova.com/solutions/grid/news/evotecoai.pdf. Retrieved 2006-03-28. 
  37. ^ "Press Release: Rutgers University Libraries Install Inferno Data Grid" (pdf). Vita Nuova. 2004-05-12. http://www.vitanuova.com/solutions/grid/news/rutgers.pdf. Retrieved 2006-03-28. 
  38. ^ "Press Release: The University of York Department of Biology install Vita Nuova's Inferno Data Grid" (pdf) (Press release). Vita Nuova. 2004-05-04. http://www.vitanuova.com/solutions/grid/news/Yorkbiology.pdf. Retrieved 2006-03-28. 
  39. ^ "plan9front - the front fell off". http://code.google.com/p/plan9front/. Retrieved 2011-12-01. 
  40. ^ "Various Licenses and Comments about Them". Free Software Foundation. http://www.gnu.org/licenses/license-list.html. Retrieved 2011-12-02. 

[edit] External links

Wikimedia Commons has media related to: Plan 9 (operating system)
Operating systems
Programming languages
Software
Publications
Other
Retrieved from "http://en.wikipedia.org/w/index.php?title=Plan_9_from_Bell_Labs&oldid=477766129"
Personal tools
Namespaces
Variants
Actions
Navigation
Interaction
Toolbox
Print/export
Languages