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IBM developerWorks: Slackware Linux 101: A look at what happens when you boot your Linux box

Mar 31, 2001, 18:30 (0 Talkback[s])
(Other stories by Joe 'Zonker' Brockmeier)

[ Thanks to Kellie for this link. ]

"Linux users are increasingly becoming power-users, which means they want to configure their system to do exactly what they want. But these days Linux distributions usually come with autoconfigured devices and start services, like Sendmail or Apache. What distributors don't take into account is that running services like Apache with their default settings intact -- unknown to the user -- is open season for crackers and script kiddies. And it eats up system resources that could be put to better use -- like more processor time for Quake or your favorite compiler. Since lack of control is a Bad Thing, let's look at what happens when a Linux system boots during the init process, at the various runlevels this involves, and how to customize your system or switch between runlevels while your system is running."

"Our examples use the Slackware Linux distribution on the x86 platform (see Resources later in this article). Most of the information carries over to other Linux distributions, but there may be some discrepancies in the specifics. In particular, Slackware's init structure is more akin to the BSD UNIX structure than the System V structure, though with the latest distribution of Slackware there are some concessions for programs that want to add services to startup but expect a System V directory structure. (See the sidebar, "The difference between BSD and System V init scripts".)"

"What actually happens when a Linux box boots up? After your computer's BIOS has done its thing, the system reads the first bit of your hard drive (or floppy, or CD-ROM, or Zip drive...Linux is very flexible) and encounters the bootloader. Usually this is the LInux LOader, better known as LILO, though GRUB and other bootloaders are becoming popular too."

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