[ 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.”