ABOUT PLAN 9

• What is Plan 9?

Plan 9 is a (relatively) new computer operating system and associated utilities. It was built by the Computing Science Research Center of Bell Laboratories (now part of Alcatel-Lucent), the same group that developed Unix, C, and C++.

Plan 9 is a distributed system, able to make use of different kinds of resources and servers spread across almost any network. It has very low resource requirement compared to most systems, has a very consistent, simple design, and performs very well.

• What is Inferno?

Inferno is a spin-off of Plan 9 using many of the same ideas (and much of the same code). Inferno has several additional benefits; even lighter resource requirements, a virtual machine (Dis), a new language for concurrent programming (Limbo), and the ability to run as an application on top of an existing Operating System (including Plan 9, Windows, and a variety of Unixes).

This FAQ mostly talks about Plan 9, but the ideas largely translate to Inferno. See the last few questions for some Inferno-specific information.

• Why do people use it?

The answer to this question varies by user; Plan 9 shows up in lots of different types of applications, making use of different benefits. It is used in embedded systems, where the low overhead is important. It is used in commercial products where the reliability and performance are important. It's used in massive supercomputers where the novel interconnections and low "system noise" are needed. What you get out of it largely depends on what you're looking for from it.

Most frequently, people using Plan 9 seem to focus on the simplicity of the system and the great distribution mechanism. This later idea, in particular, is very central to Plan 9: all resources are represented as normal files (as opposed to Unix, where most things are files, but not all files are "real" files), and the system uses a common method to talk to them all (9P, a.k.a. Styx). This, and related points like the fact that the namespace is per-process, affects the organization of the entire system, leading to all sorts of interesting, novel uses. This is the key point to understand in Plan 9, and also the biggest mental jump from Unix or other systems.

• Why don't more people use it?

Plan 9 is not Unix (or anything else you're likely familiar with). While the command set is superficially similar, it's most certainly not the same (cat on Unix has a dozen or so options; on Plan 9, it has zero). Many people come to Plan 9 expecting unix++ or similar, and are disappointed when they find something much more different than that. Even the development environment is similar but entirely distinct: we use mk, not make; we use C, but the library isn't ANSI and our compilers understand some C extensions that aren't in GCC (and not most of the non-standard ones that GCC made up); the default preprocessor is much simpler than ANSI's.

There are also some very specific issues with using Plan 9 as your primary OS, mostly relating to application support. We don't have a GUI word processor, a spreadsheet program, or popular games. Most notably, we don't have a "modern" web browser with CSS and JavaScript support (but see the question about some of those below). Plan 9 does not aim to replace any existing desktop system, and thus using it has a higher initial bar than using systems which do try to fill such a roll.

• Is there much of a community? Where?

The Plan 9 community is small but active. The best places to find it are the 9fans mailing list and in #plan9 on Freenode. Several people in both places have been using Plan 9 for a decade or more, and the mailing list in particular gets occasional traffic from the original authors.

• Where can I get more information on the system?

The man pages and papers for the system are available online. The wiki has a lot of good information, although the organization is not always as good as it could be.

GETTING STARTED WITH PLAN 9

• Sounds Interesting. Now What?

Read the papers. Read the installation instructions and hardware requirements. Decide what your installation will look like. Download the distribution. Install the system.

• Can I use this particular application I've got?

Maybe. Before you start, remember that this is not Unix; first look for the Plan 9 way of solving whatever problem it is your Unix application is addressing. Source or binary compatibility with Unix has never been a design goal of Plan 9, so every solution is imperfect. Still, there are times when it's needed, so there are solutions which work well in many cases.

If you've got source for the application, it's reasonably self-contained, and reasonably standards-compliant, you've got a good shot at being able to compile it within Plan 9 using APE, the ANSI/Posix Environment. This gives you a full ANSI C pre-processor, make, a POSIX shell, and a bunch of related tools. The "configure" script for some applications work "out of the box", although many make bad assumptions about linux-specific features.

If you don't have the source or building it on Plan 9 is otherwise infeasable, linuxemu may be of help. This will emulate enough of the linux kernel and system call interface to allow a wide variety of linux applications to run. See the documentation for particular shortcomings.

Related to the above, there is also an X11 server for Plan 9 called equis. It is available from fgb's contrib directory (see below).

• Can I run KDE/GNOME/enlightenment/&c?

Almost certainly not. Remember: Plan 9 is not Unix. While it's true that we have APE and an X11 environment for importing foreign applications or running applications on Unix systems with local display, very large programs like these typically have a slew of dependencies. If possible at all, it would be a lot of work.

The spartan nature of the Plan 9 user interface is one of the first things which strikes newcomers. There are no desktop icons, almost no window decoration, no configuration files, and no Start menu. The simplistic interface is not due to lack of attention, but is rather a conscious design decision. The Plan 9 interfaces follow a "get out of my way" philosophy which, in many ways, runs exactly counter to the common desktop environments on other systems.

• Can I run Mozilla/Firefox/Opera/&c?

The short answer is "no"; the long answer is "kinda". These won't run on Plan 9 directly, but you might have good luck with running them within linuxemu. Firefox, Opera, and dillo, at least, have been shown to work this way, although there are some restrictions on which version of glibc they're built against.

USING PLAN 9

• Okay, it's installed. Now what?

First off, if you've not read the papers, do so. They're available in your new installation under /sys/doc, as well as online. Particularly useful are 9.ps, names.ps, acme/acme.ps, auth.ps, fossil.ps, and plumb.ps, in roughly that order, although they're all worth a read.

Remember that this is not Unix, even though it will sometimes feel like it. Make frequent use of the man pages. They're both more concise and more useful than on most Unix systems.

NOT USING PLAN 9

• It's really interesting, but I don't have supported hardware. Options?

First, note that Plan 9 runs well in a variety of virtualization systems, including Parallels, VMWare, Xen, and lguest. If hardware support is your primary issue, one of those might solve your problem.

If that's not an option for whatever reason, and you're on some flavor of Unix (including Mac OS X), check out 9vx - a Plan 9 kernel running as an application above Unix. It's not as stable as the "real thing" and has a few quirks, but it works very well for lots of cases.

• The ideas sound great, but I don't want a whole new OS. Options?

You can get at many of the Plan 9 ideas without actually running Plan 9. The most complete way is probably Inferno, which in addition to running on bare hardware can run as an application on top of an existing OS. You'll get the same resource distribution mechanism, the same great clean code, and many of the same tools, and Limbo and Dis on top of that. In fact, Limbo on its own probably makes Inferno worth checking out regardless of what you end up doing with Plan 9 (remember you can run Inferno on top of Plan 9, Unix, or Windows).

Beyond that, there are a number of ways to get at bits and piecse of the ideas of Plan 9 in other systems. If you're interested in the cleaner, more consistent user or programming environments, check out Plan 9 from User Space, a port of many of the Plan 9 tools and libraries to various Unix-like systems. If you're interested in using 9P to distribute resources, check out v9fs, a Linux kernel module implementing 9P, or one of the many 9P implementations in various languages.

• How can I help, anyway?

If you're using one of the alternatives discussed in the previous few questions, there are still good ways you can help. If you're a Unix user, particularly a Linux user, you could package Plan 9 from User Space or Inferno for your particular system. For "extra credit", try to get the results included in the base system. If you're a Windows developer, you could work on porting 9vx or Plan 9 from User Space to Windows. And if you're using Inferno, the best answers are largely the same as if you're using Plan 9 itself: the best contribution is to use the system to solve a problem, and to write, code and documentation. And if your'e a developer in some language other than C or Limbo, it's likely that we could use work on the 9P/Styx implemenation in that language, especially authentication.