Chapter 1. Introduction
"In the beginning, the file was without
form, and void; and emptiness was upon the face of the bits.
And the Fingers of the Author moved upon the face of the
keyboard. And the Author said, Let there be words, and there
The Linux System Administrator's Guide,
describes the system administration aspects of using Linux.
It is intended for people who know next to nothing about system
administration (those saying ``what is it?''), but who have already
mastered at least the basics of normal usage. This manual
doesn't tell you how to install Linux; that is described in the
Installation and Getting Started document. See below for more
information about Linux manuals.
System administration covers all the things that you have to
do to keep a computer system in usable order. It includes
things like backing up files (and restoring them if necessary),
installing new programs, creating accounts for users (and deleting
them when no longer needed), making certain that the filesystem
is not corrupted, and so on. If a computer were, say, a house,
system administration would be called maintenance, and would
include cleaning, fixing broken windows, and other such things.
The structure of this manual is such that many of the
chapters should be usable independently, so if you need information
about backups, for example, you can read just that chapter. However,
this manual is first and foremost a tutorial and can be read
sequentially or as a whole.
This manual is not intended to be used completely
independently. Plenty of the rest of the Linux documentation is also
important for system administrators. After all, a system
administrator is just a user with special privileges and duties.
Very useful resources are the manual pages, which should always be
consulted when you are not familiar with a command. If you do not
know which command you need, then the apropos
command can be used. Consult its manual page for more details.
While this manual is targeted at Linux, a general principle
has been that it should be useful with other UNIX based operating
systems as well. Unfortunately, since there is so much variance
between different versions of UNIX in general, and in system
administration in particular, there is little hope to cover
all variants. Even covering all possibilities for Linux is
difficult, due to the nature of its development.
There is no one official Linux distribution, so different
people have different setups and many people have a setup they
have built up themselves. This book is not targeted at any
one distribution. Distributions can and do vary considerably.
When possible, differences have been noted and alternatives
given. For a list of distributions
and some of their differences see
In trying to describe how things work, rather than just
listing ``five easy steps'' for each task, there is much information
here that is not necessary for everyone, but those parts are marked
as such and can be skipped if you use a preconfigured system.
Reading everything will, naturally, increase your understanding of
the system and should make using and administering it more
Understanding is the key to success with Linux. This book
could just provide recipes, but what would you do when confronted by
a problem this book had no recipe for? If the book can provide
understanding, then recipes are not required. The answers will be self
Like all other Linux related development, the work
to write this manual was done on a volunteer basis: I did it because
I thought it might be fun and because I felt it should be done.
However, like all volunteer work, there is a limit to how much time,
knowledge and experience people have. This means that the manual is
not necessarily as good as it would be if a wizard had been paid
handsomely to write it
and had spent millennia to perfect it. Be warned.
One particular point where corners have been cut is that
many things that are already well documented in other freely
available manuals are not always covered here. This applies
especially to program specific documentation, such as all the
details of using mkfs. Only the purpose of the
program and as much of its usage as is necessary for the purposes of
this manual is described. For further information, consult these
other manuals. Usually, all of the referred to documentation is
part of the full Linux