2.2.2. General remarks
You type these commands after the prompt, in a terminal window
in graphical mode or in text mode, followed by Enter.
Commands can be issued by themselves, such as ls. A command behaves different when you specify an
option, usually preceded with a dash (-), as in ls -a. The same option character may have a different
meaning for another command. GNU programs take long options,
preceded by two dashes (--), like ls --all.
Some commands have no options.
The argument(s) to a command are specifications for the
object(s) on which you want the command to take effect. An example
is ls /etc, where the directory /etc is the argument to the ls command. This indicates that you want to see the
content of that directory, instead of the default, which would be
the content of the current directory, obtained by just typing
ls followed by Enter.
Some commands require arguments, sometimes arguments are
You can find out whether a command takes options and arguments,
and which ones are valid, by checking the online help for that
In Linux, like in UNIX, directories are separated using forward
slashes, like the ones used in web addresses (URLs). We will
discuss directory structure in-depth later.
The symbols . and .. have special meaning when directories are
concerned. We will try to find out about those during the
exercises, and more in the next chapter.
Try to avoid logging in with or using the system administrator's
account, root. Besides doing your normal work, most tasks,
including checking the system, collecting information etc., can be
executed using a normal user account with no special permissions at
all. If needed, for instance when creating a new user or installing
new software, the preferred way of obtaining root access is by
switching user IDs, see
Section 3.2.1 for an
Almost all commands in this book can be executed without system
administrator privileges. In most cases, when issuing a command or
starting a program as a non-privileged user, the system will warn
you or prompt you for the root password when root access is
required. Once you're done, leave the application or session that
gives you root privileges immediately.
Reading documentation should become your second nature.
Especially in the beginning, it is important to read system
documentation, manuals for basic commands, HOWTOs and so on. Since
the amount of documentation is so enormous, it is impossible to
include all related documentation. This book will try to guide you
to the most appropriate documentation on every subject discussed,
in order to stimulate the habit of reading the man pages.