Small Systems and Big Iron: Linux on Non-x86 Computers
Thousands of Linux distributions run on Intel-compatible x86 PCs, but these systems actually make up only a minority of the computers produced. Other architectures, such as MIPS, SPARC, ARM, Power and Intel's Itanium chip are used heavily in certain applications. These computers historically have been the domain of high-end UNIX variants or specialized embedded operating systems, but Linux has taken both embedded systems and big-iron server systems by storm. In this article, I explain the important Linux distributions for ARM, IBM Power and Intel Itanium and their features.
ARM is the world's most-popular 32-bit processor. TVs, set-top boxes, portable devices and large numbers of other device categories contain ARM processors. They also are starting to be used in Netbooks due to the poor performance and high power consumption of the Intel Atom processor. ARM chips are popular due to their simple design, decent performance, low power consumption and for the massive amount of code that already runs on the architecture.
Most ARM processors, especially lower-end ones, run tiny real-time operating systems like QNX and VxWorks. On higher-end devices, however, Linux is becoming a major player. Google's successful Android cell-phone OS is a Linux system, although a heavily customized one. Nokia also supports Linux on its high-end smartphones and Internet tablets with its Maemo operating system, a Debian derivative with hundreds of Linux programs ported to it.
For hobbyists, the choice of distribution for ARM largely is defined by the available hardware. Most hobbyists do not have the time or resources to design their own Linux ARM board and develop a board support package for it, but a few hobbyist-friendly Linux hardware platforms have been developed.
The most popular ARM Linux distribution for hobbyists is Ångström, built by a merger of several older embedded Linux projects. Ångström uses a low-overhead package manager called ipkg, similar to the dpkg system used in Debian. An interesting feature of this distribution is the ability to generate a custom system image on the Web site, with user-defined packages and capabilities. During the past few months, developers have released plenty of software as Ångström packages, including GNOME, Firefox, GIMP, Quake, Mono and dozens of other pieces of software. Ångström also is used as the base for other embedded Linux distributions.
Starting with version 9.04, Ubuntu officially supports the ARM platform. Canonical releases images only for a fairly obscure Freescale development board, but the Linux community has created ports to numerous other ARM computers, including the BeagleBoard and the N800 and N810 Internet tablets. Sharp even released an Ubuntu/ARM Netbook in Japan, the PC-Z1 NetWalker; however, it received a poor reception due to substandard build quality and a miniscule optical trackpad.
As Canonical is investing considerable resources into the Ubuntu ARM port, it is expected to become significant as an OS for Netbooks and similar devices in the future. If you have compatible hardware, the Ubuntu ARM port is of very high quality. If you're interested in experimenting but don't have compatible hardware, Ubuntu also can be run in QEMU. Ubuntu's wiki has tutorials for doing so, although the procedure is somewhat complicated.
Quite a few mobile Internet devices and other small computer systems are using Ubuntu or Ubuntu variants as their default operating system, and you can expect Ubuntu for ARM to become even more important as Canonical invests more money into its continued development.
Nokia's Maemo platform has received quite a bit of attention lately. It originally was released on the company's N770 tablet and was used by its successors: the N800/N810 Internet tablets and the N900 smartphone. Heavy interest developed in the platform after its use in the N900. Maemo is a full-featured Debian system with a custom user interface. It uses a stripped-down X server, KDrive and a touchscreen-friendly GTK-based desktop environment called Hildon. Nokia also provides Scratchbox, a package containing an SDK and emulator. Unlike most consumer embedded platforms, Maemo automatically can update itself with its APT-based package management system.
Although Nokia supports Maemo only on its Internet tablet systems, its components are being ported to other operating systems and devices. A community project, Mer, exists to develop a new distribution based on code from both Maemo and Ubuntu and to port the new system to a wide variety of mobile devices with both ARM and x86 processors. Maemo probably still is a superior operating system on the Internet tablets due to its high level of completeness, but Mer is under heavy development and becomes more polished with every release.
The Android operating system, developed by Google and its partners, is probably the fastest-growing operating system for smartphones and is becoming increasingly popular on tablet computers, such as the Dell Mini 5. Analysts predict that hundreds of millions of devices will ship running Android in the next few years, making it one of the most important embedded operating systems. Android runs a Linux kernel and has a basic shell, but in other ways, it's very different from most Linux distributions. It uses a custom window system that's very different from X11, which is what most users and developers are used to. It has a high-level application framework, WindowManager, that is backed by a low-level library called SurfaceManager. Android applications are written in Java and executed by the Dalvik Virtual Machine, which is designed to have a low memory footprint and lacks Just-in-Time Compilation, which is an optimization feature provided by most mainstream Java virtual machines. Clever developers and hobbyists have found that Android is easily tweakable, and have figured out how to run OpenSSH and X11 on the platform for those who prefer a more traditional Linux environment.
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