Kernel 2.4 - what's in store?

Linux enthusiasts have long awaited the release of Linux kernel 2.4. All aspects of Linux usage have been closely considered in the development of 2.4 and the kernel has been optimised along those lines, from entry level to enterprise. The results will bring considerable weight to the push for Linux in business computing as commercial quality Unix features continue to be offered in an open source model.

New architectures

The development of 2.4 focused strongly on supporting new hardware and CPU level architectures. Three new hardware architectures have been introduced: IA-64, Intel's 64-bit Itanium processor; S/390, an IBM mainframe architecture; and the SuperH processor architecture, used by the Windows CE hardware. 2.4 has also been optimised for Crusoe, the new lightweight chip from Transmeta.

Linux Itanium development has attracted a lot of attention from big business. Contributions have been made by Hewlett-Packard, IBM, Intel, VA Linux, Red Hat, SuSE, TurboLinux, SGI, LinuxCare and many others. With this, Linux looks set to support extensively IA-64 architecture from the minute Intel begins shipping - which could be as early as late this year. (More information can be found at implementation of Linux on S/390 is just as exciting. Mainframe technology is very different from that of the PC, allowing many virtual computers to run simultaneously on a single, extremely large computer. Thanks to significant contributions by IBM and SuSE, Linux can now run directly on the S/390 hardware or virtually on top of the S/390 operating system. This is useful for companies with existing mainframe commitments which want to deploy Linux servers extensively, or Web hosts and ASPs which need to deploy constantly Unix servers. Mainframe allows for significant space savings - it does not take up more room if you add another computer. IBM and Linux S/390 developers have already demonstrated 60,000 concurrent Linux instances running on a mainframe.

File systems are us?

Linux already supports many file systems, including the default ext2, MS-DOS, VFAT and FAT32 (Windows 9x), NTFS (Windows NT), Apple Macintosh and OS/2 HPFS. Building on this base, Linux 2.4 adds a number of new systems, including kernel level support of UDF, used on DVDs; EFS, used on some SGI systems; UFS, which is used by many commercial Unix systems such as SunOS and NeXTStep; and extended support for a RAM-mapped file system, which allows users to read and write directly to RAM hundreds of times faster than via conventional means.

Unfortunately, the XFS, JFS and ReiserFS journal file system projects have not made it into the stable kernel, but should be in 2.6. For more information see

How about hardware?

More than half the work on Linux 2.4 has been in the area of drivers for hardware devices, particularly that of the Universal Serial Bus (USB). USB lets an arbitrary external device with a USB port be connected, disconnected and swapped with other devices while the computer is running. USB devices which are already shipping include keyboards, mice, speakers, headphones, scanners and printers. This is a much more efficient way of using external devices and appeals to the home and server market alike.

Two kernel projects are also working to universalise the production of device drivers. The first is complete ISA Plug and Play support for Linux. The second is an Intelligent Input/Output (I2O) system which will facilitate the writing and implementation of platform-independent drivers - a concept which has long been struggling to get off the ground in the PC industry.

Networking at the core

The entire networking core has been rewritten and is totally multi-threaded, which means significant speed increases, especially on multi-processor systems and with gaming. The work has also resulted in the delivery of a commercial-quality IP filtering subsystem, IP Tables, which replaces ipchains in the 2.2 kernel. A basic kernel level Web server has also been included to show the power of the new core.

Geek value

Some aspects of Linux 2.4 seem to exist for their sheer geek value. The kernel supports 64GB of physical RAM under PC architecture, for example. It can also power more than 16 Ethernet cards on the same machine. In total, 10 IDE controllers can be used. Thought that was a lot? The new kernel can handle up to 2.4 billion users on one system - that's a lot of users!

All up, Linux 2.4 is set to bring cutting-edge technologies to all Linux users. Whether you use it at home, in the business environment or to power enterprise applications, Linux 2.4 aims to get you there and deliver every time.

The Caldera Technology Preview distribution was used to test the potential of 2.4 for this review. See more at

Linux 2.4 should be available by the end of October. Pre-release versions have been included on the CD this month.

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Gavin Sherry

PC World
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