From the Editor

Welcome to Linux Journal's kernel issue. Though it's true what Ted Ts'o says in this month's interview about the more exciting work in the Linux community happening in user space than in the kernel, there are still enough intriguing developments in the kernel to merit devoting an issue to it.

In fact, some of the most exciting recent kernel developments are covered in this month's pages. Last month we ran Rick Lehrbaum's interview with the preemptible kernel patch maintainer, Robert Love. This month Robert wrote a feature article explaining just how the patch lowers latency and how this translates to performance benefits, not only for those needing real-time efficiency, but also for regular users.

Greg Kroah-Hartman, the Linux USB and PCI Hot Plug kernel maintainer, reveals how the Linux kernel, as of 2.4.15, handles the kernel-level difficulties associated with hot-pluggable devices by way of the PCI Hot Plug driver core.

While iptables are no longer the latest in kernel development, the Netfilter code is constantly evolving, and many are still struggling with iptables building. Last year for our kernel issue David A. Bandel wrote an introductory-level article on Netfilter. He received a deluge of e-mail requesting further guidance. So to satisfy our readership, David delves into more advanced iptables building. Look for a further sequel to David's article in next month's Kernel Korner.

Continuing in a security vein, Michael Bacarella explains how POSIX capabilities in the Linux kernel can provide a useful middle-ground permission level that grants more liberal permissions than a standard user, but not the potentially harmful level of root.

In our last feature article, David Frascone brings us to the border of user land and the kernel by explaining the benefits of kernel module debugging with User-Mode Linux. UML provides something of a virtual machine for safer debugging.

Speaking of user land, one of the more intriguing developments there, at least for our production staff at Linux Journal, may be the Scribus Project ( Here at Linux Journal we try to practice what we preach, and everyone from the accountant to the receptionist, to the marketing and editorial departments do their work on Linux workstations. The only thing we don't do on Linux is magazine layout. Hopefully the Scribus Project will allow us to change that.

Scribus is a GPLed layout program for Linux. It's still in its early stages of development with a team of three—two of whom do the documentation, leaving all the programming to Franz Schmid. Franz is currently working on adding new object types like curves, polygons, etc. The team's goal is to match the quality of programs such as Adobe PageMaker and QuarkXPress.

I'm sure Franz wouldn't object if someone wanted to lend a hand. He can be reached at

Richard Vernon is editor in chief of Linux Journal.