Manual

1. A few characteristics

• A multi-user connection-oriented system.
• Users and groups.
• Concept of superuser (root).
• Login: alphanumerical, maximum of eight characters is a UNIX standard (more so in the case of Linux).
• Password: assigned by root, user-modifiable.
• Case-sensitivity (UPPER-CASE/lower-case).
• Interfaces: text (shell) or graphical (X/Window).
• Default shell is BASH (Bourne Again SHell).

2. Users and groups

• To connect to a Linux system, the user must be created on the system by the administrator (root).
• Each user possesses attributes on the system: name, password, groups, work directory (the home directory), a default shell.
• A user belongs to a main group and then to a number of secondary groups.

3. Shell prompt (invite)

The shell's invite (for bash, in this case) appears as follows:

[jane@name_machine /home/jane]$

By default, the $ (dollar) symbol is used at the end of the invite for any connection initiated by ordinary users. When the connection is established by the superuser (root), the symbol used at the end of the invite is then the # (number sign) symbol.

[root@name_machine /root]#

4. A few commands and basic concepts

• The “/” (slash) symbol serves as a separator character in paths.
• The root directory of the tree structure is the “/” directory.
• Commands previously entered on the shell can be recalled using the keyboard's up and down arrow buttons.

Basic commands

The pwd (print working directory) command displays the path of the current directory.

The ls (listing) command displays a list of files and sub-directories of the current working directory, or that of the directory path given as argument.

The cd (change directory) command changes the current working directory, allowing to move within the tree structure.

The date command displays or sets the system time and date.

5. Basic directories

6. Online documentation

The online documentation can be very useful for obtaining information on:

• The purpose of a command
• The syntax and options of a command
• How-to for an application

We can obtain this documentation from various sources:

• The manual: the man command
• Info files: the info command
• HOW-TOs and hands-on documentation: the /usr/share/doc/ directory.

The manual: the man command

Accessing the manual page:

man [command]
man [option] [command]

$ man ls
$ man man
$ man -S5 passwd,
$ man -k keyword

Information layout on a manual page

Here is the presentation layout schema used in the manual: