This page is provided as a convenient way to download. It should also be helpful for people on dial-up to have one big page to read. A list of the other “AllOfs” can be found at http://linuxbasics.org/course/book/allallofs.

Please take into considerations that once you save this page, it cannot keep up with the dynamics of the wiki. If you find something to be corrected or improved, you need to check or edit the actual current wiki-page.

The current version of this document can be found at http://linuxbasics.org/course/book/index.

This book is licensed and may be distributed under the terms of the GNU Free Documentation License. A copy of the license can be found at http://linuxbasics.org/course/book/allof_appendix

Usually, these snapshots are updated daily between 05:00 and 05:15 UTC

This snapshot was created: Sun Jul 20 06:08:07 CEST 2008

• 2.1. Logging in, activating the user interface and logging out
  • 2.1.1. Introduction
  • 2.1.2. Graphical mode
  • 2.1.3. Text mode
• 2.2. Absolute basics
  • 2.2.1. The commands
  • 2.2.2. General remarks
  • 2.2.3. Using Bash features
• 2.3. Getting help
  • 2.3.1. Be warned
  • 2.3.2. The man pages
  • 2.3.3. More info
• 2.4. Summary
• 2.5. Exercises
  • 2.5.1. Connecting and disconnecting
  • 2.5.2. Passwords
  • 2.5.3. Directories
  • 2.5.4. Files
  • 2.5.5. Getting help
  • Answer Key

In order to get the most out of this guide, we will immediately start with a practical chapter on connecting to the Linux system and doing some basic things.

We will discuss:

• Connecting to the system
• Disconnecting from the system
• Text and graphic mode
• Changing your password
• Navigating through the file system
• Determining file type
• Looking at text files
• Finding help

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In order to work on a Linux system directly, you will need to provide a user name and password. You always need to authenticate to the system. As we already mentioned in the exercise from Chapter 1, most PC-based Linux systems have two basic modes for a system to run in: either quick and sober in text console mode, which looks like DOS with mouse, multitasking and multi-user features, or in graphical mode, which looks better but eats more system resources. But modern computers should be able to handle a GUI easily.

This is the default nowadays on most desktop computers. You know you will connect to the system using graphical mode when you are first asked for your user name, and then, in a new window, to type your password.

To log in, make sure the mouse pointer is in the login window, provide your user name and password to the system and click OK or press Enter.

• Careful with that root account!
  • It is generally considered a bad idea to connect (graphically) using the root user name, the system adminstrator’s account, since the use of graphics includes running a lot of extra programs, in root’s case with a lot of extra permissions. To keep all risks as low as possible, use a normal user account to connect graphically. But there are enough risks to keep this in mind as a general advice, for all use of the root account: only log in as root when extra privileges are required.
  • Some distributions, like Ubuntu for example, will not set up a root-account. They use a programm called “sudo” to get administrative privileges when needed. Here, everytime you are about to do things that require root-privileges, you need to enter your user’s password.

The time it takes for your system to come up after you have entered your user name and password will depend on the speed of your processor, the window manager and personal settings.

To continue, you will need to open a terminal window or xterm for short (X being the name for the underlying software supporting the graphical environment). This program can be found in the Applications→Utilities, System Tools or Internet menu, depending on what window manager you are using. There might be icons that you can use as a shortcut to get an xterm window as well, and clicking the right mouse button on the desktop background will usually present you with a menu containing a terminal window application.

While browsing the menus, you will notice that a lot of things can be done without entering commands via the keyboard. For most users, the good old point-’n’-click method of dealing with the computer will do. But we want to learn the basics of Linux, and be able to meddle with the heart of the system. That is why we need a stronger tool than a mouse to handle all the tasks we will face. This tool is the shell, and when in graphical mode, we activate our shell by opening a terminal window.

The terminal window is your control panel for the system. Almost everything that follows is done using this simple but powerful text tool. A terminal window should always show a command prompt when you open one. This terminal shows a standard prompt, which displays the user’s login name, and the current working directory. In this case, it is the user’s home directory which is represented in most of the distributions by the twiddle or tilde (~):

Figure 2-1. Terminal window

Another common form for a prompt is this one:

[user@host dir]

In the above example, user will be your login name, host the name of the machine you are working on, and dir an indication of your current location in the file system.

Later we will discuss prompts and their behavior in detail. For now, it suffices to know that prompts can display all kinds of information, but that they are not part of the commands you are giving to your system.

To disconnect from the system in graphical mode, you need to close all terminal windows and other applications. After that, hit the logout icon or find Log Out in the menu. Closing everything is not really necessary, and the system can do this for you, but session management might put all currently open applications back on your screen when you connect again, which takes longer and is not always the desired effect. However, this behavior is configurable.

When you see the login screen again, asking to enter user name and password, logout was successful.

You know you’re in text mode when the whole screen is black, showing (in most cases) white characters. A text mode login screen typically shows some information about the machine you are working on, the name of the machine and a prompt waiting for you to log in:

RedHat Linux Release 8.0 (Psyche)

blast login: _

The login is different from a graphical login, in that you have to hit the Enter key after providing your user name, because there are no buttons on the screen that you can click with the mouse. Then you should type your password, followed by another Enter. You won’t see any indication that you are entering something, not even an asterisk, and you won’t see the cursor move. But this is normal on Linux and is done for security reasons.

When the system has accepted you as a valid user, you may get some more information, called the message of the day (motd), which can be anything. Additionally, it is popular on UNIX systems to display a fortune cookie, which contains some general wise or unwise (this is up to you) thoughts. After that, you will be given a shell, indicated with the same prompt that you would get in graphical mode.

• Don’t log in as root
  • Also in text mode: log in as root only to do setup and configuration that absolutely requires administrator privileges, such as adding users, installing software packages, and performing network and other system configuration. Once you are finished, immediately leave the special account and resume your work as a non-privileged user. Alternatively, some systems, like Ubuntu, force you to use sudo, so that you do not need direct access to the administrative account.

Logging out is done by entering the logout command, followed by Enter. You are successfully disconnected from the system when you see the login screen again.

• The power button
  • While Linux was not meant to be shut off without application of the proper procedures for halting the system, hitting the power button is equivalent to starting those procedures on newer systems. However, powering off an old system without going through the halting process might cause severe damage! If you want to be sure, always use the Shut down option when you log out from the graphical interface, or, when on the login screen (where you have to give your user name and password) look around for a shutdown button.

Now that we know how to connect to and disconnect from the system, we’re ready for our first commands.

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These are the quickies, which we need to get started; we will discuss them later in more detail.

Table 2-1. Quickstart commands

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 differently 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 you want to display the content of the /etc directory rather than the default, which is the content of the current directory, obtained by just typing ls followed by Enter. Some commands require arguments, sometimes arguments are optional.

You can find out whether a command takes options and arguments, and which ones are valid, by checking the online help for that command, see Section 2.3.

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 example.

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, in which you used your 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.

Several special key combinations allow you to do things easier and faster with the GNU shell, Bash, which is the default on almost any Linux system, see Section 3.2.3.2. Below is a list of the most commonly used features; it is strongly suggested that you make a habit out of using them, so as to get the most out of your Linux experience from the very beginning.

Table 2-2. Key combinations in Bash

The last two items in the above table may need some extra explanations. For instance, if you want to change into the directory directory_with_a_very_long_name, you are not going to type that very long name. You just type on the command line cd dir, then you press Tab and the shell completes the name for you, if no other files are starting with the same three characters. Of course, if there are no other items starting with d, then you might just as well type cd d and then Tab. If more than one file starts with the same characters, the shell will signal this to you, upon which you can hit Tab again, and the shell presents the choices you have:

your_prompt>  cd st 

starthere	 stuff		stuffit 

In the above example, if you type “a” after the first two characters and hit Tab again, no other possibilities are left, and the shell completes the directory name, without you having to type the string rthere:

your_prompt> cd starthere

Of course, you’ll still have to hit Enter to accept this choice.

In the same example, if you type “u”, and then hit Tab, the shell will add the “ff” for you, but then it protests again, because multiple choices are possible. If you type Tab Tab again, you’ll see the choices; if you type one or more characters that make the choice unambiguous to the system, and Tab again, or Enter when you’ve reach the end of the file name that you want to choose, the shell completes the file name and changes you into that directory - if indeed it is a directory name.

This works for all file names that are valid arguments to commands. For instance, if you have a text file stuff.txt, it will not affect completion for a cd command, since it is not a directory.

The same goes for command name completion. Typing ls and then hitting the Tab key twice, lists all the commands in your PATH (see Section 3.2.1) that start with these two characters:

your_prompt> ls

ls           lsdev        lspci        lsraid       lsw   
lsattr       lsmod        lspgpot      lss16toppm   lsb_release  
lsof         lspnp        lsusb 

Prev: Logging in, activating the user interface and logging out
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Next: Getting help====== 2.3. Getting help ======

GNU/Linux is all about becoming more self-reliant. And as usual with this system, there are several ways to achieve the goal. A common way of getting help is finding someone who knows, and however patient and peace-loving the Linux-using community will be, almost everybody will expect you to have tried one or more of the methods in this section before asking them, and the ways in which this viewpoint is expressed may be rather harsh if you prove not to have followed this basic rule.

A lot of beginning users fear the man (manual) pages, because they are an overwhelming source of documentation. They are, however, very structured, as you will see from the example below on: man man.

Reading man pages is usually done in a terminal window when in graphical mode, or just in text mode if you prefer it. Type the command like this at the prompt, followed by Enter:

The documentation for man will be displayed on your screen after you press Enter:

man(1)                                                         man(1)



NAME
 man - format and display the on-line manual pages
 manpath - determine user's search path for man pages

SYNOPSIS
 man [-acdfFhkKtwW] [--path] [-m system] [-p string] [-C config_file]
 [-M pathlist] [-P pager] [-S section_list] [section] name ...


DESCRIPTION
 man formats and displays the on-line manual pages.  If you specify
 section, man only looks in that section of the manual.  
 name is normally the name of the manual page, which is typically the 
 name of a  command, function, or file.  However, if name contains a 
 slash (/) then man interprets it as a file specification, so that you
 can do man ./foo.5 or even man /cd/foo/bar.1.gz.

 See  below  for  a  description  of where man looks for the manual
 page files.

OPTIONS
 -C  config_file
lines 1-27

Browse to the next page using the space bar. You can go back to the previous page using the b-key. When you reach the end, man will usually quit and you get the prompt back. Type q if you want to leave the man page before reaching the end, or if the viewer does not quit automatically at the end of the page.

• Pagers
  • The available key combinations for manipulating the man pages depend on the pager used in your distribution. Most distributions use less to view the man pages and to scroll around. See Section 3.3.4.2 for more info on pagers.

Each man page usually contains a couple of standard sections, as we can see from the man man example:

• The first line contains the name of the command you are reading about, and the id of the section in which this man page is located. The man pages are ordered in chapters. Commands are likely to have multiple man pages, for example the man page from the user section, the man page from the system admin section, and the man page from the programmer section.
• The name of the command and a short description are given, which is used for building an index of the man pages. You can look for any given search string in this index using the apropos command.
• The synopsis of the command provides a technical notation of all the options and/or arguments this command can take. You can think of an option as a way of executing the command. The argument is what you execute it on. Some commands have no options or no arguments. Optional options and arguments are put in between [ and ] to indicate that they can be left out.
• A longer description of the command is given.
• Options with their descriptions are listed. Options can usually be combined. If not so, this section will tell you about it.
• Environment describes the shell variables that influence the behavior of this command (not all commands have this).
• Sometimes sections specific to this command are provided, such as the CAT PAGES section in the example.
• A reference to other man pages is given in the SEE ALSO section. In between parentheses is the number of the man page section in which to find this command. Experienced users often switch to the SEE ALSO part using the / command followed by the search string SEE and press Enter.
• Usually there is also information about known bugs (anomalies) and where to report new bugs you may find.
• There might also be author and copyright information.

Some commands have multiple man pages. For instance, the passwd command has a man page in section 1 and another in section 5. By default, the man page with the lowest number is shown. If you want to see another section than the default, specify it after the man command:

man 5 passwd

If you want to see all man pages about a command, one after the other, use the -a to man:

man -a passwd

This way, when you reach the end of the first man page and press SPACE again, the man page from the next section will be displayed.

In addition to the man pages, you can read the info pages about a command, using the info command. These usually contain more recent information and are somewhat easier to use. The man pages for some commands refer to the info pages.

Get started by typing info info in a terminal window:

File: info.info,  Node: Top,  Next: Getting Started,  Up: (dir)

Info: An Introduction
*********************

   Info is a program, which you are using now, for reading
documentation of computer programs.  The GNU Project distributes most
of its on-line manuals in the Info format, so you need a program called
"Info reader" to read the manuals.  One of such programs you are using
now.

   If you are new to Info and want to learn how to use it, type the
command `h' now.  It brings you to a programmed instruction sequence.

   To learn advanced Info commands, type `n' twice.  This brings you to
`Info for Experts', skipping over the `Getting Started' chapter.

* Menu:

* Getting Started::             Getting started using an Info reader.
* Advanced Info::               Advanced commands within Info.
* Creating an Info File::       How to make your own Info file.
--zz-Info: (info.info.gz)Top, 24 lines --Top-------------------------------
Welcome to Info version 4.2. Type C-h for help, m for menu item.

Use the arrow keys to browse through the text and move the cursor on a line starting with an asterisk, containing the keyword about which you want info, then hit Enter. Use the P and N keys to go to the previous or next subject. The space bar will move you one page further, no matter whether this starts a new subject or an info page for another command. Use Q to quit. The info program has more information.

A short index of explanations for commands is available using the whatis command, like in the examples below:

ls                   (1)  - list directory contents

This displays short information about a command, and the first section in the collection of man pages that contains an appropriate page.

If you don’t know where to get started and which man page to read, apropos gives more information. Say that you don’t know how to start a browser, then you could enter the following command:

Galeon [galeon](1)  - gecko-based GNOME web browser
lynx           (1)  - a general purpose distributed information browser 
	            for the World Wide Web
ncftp          (1)  - Browser program for the File Transfer Protocol
opera          (1)  - a graphical web browser
pilot          (1)  - simple file system browser in the style of the 
		    Pine Composer
pinfo          (1)  - curses based lynx-style info browser
pinfo [pman]   (1)  - curses based lynx-style info browser
viewres        (1x)  - graphical class browser for Xt

After pressing Enter you will see that a lot of browser related stuff is on your machine: not only web browsers, but also file and FTP browsers, and browsers for documentation. If you have development packages installed, you may also have the accompanying man pages dealing with writing programs having to do with browsers. Generally, a command with a man page in section one, so one marked with (1), is suitable for trying out as a user. The user who issued the above apropos might consequently try to start the commands galeon, lynx or opera, since these clearly have to do with browsing the world wide web.

Most GNU commands support the --help, which gives a short explanation about how to use the command and a list of available options. Below is the output of this option with the cat command:

Usage: cat [OPTION] [FILE]...
Concatenate FILE(s), or standard input, to standard output.

  -A, --show-all           equivalent to -vET
  -b, --number-nonblank    number nonblank output lines
  -e                       equivalent to -vE
  -E, --show-ends          display $ at end of each line
  -n, --number             number all output lines
  -s, --squeeze-blank      never more than one single blank line
  -t                       equivalent to -vT
  -T, --show-tabs          display TAB characters as ^I
  -u                       (ignored)
  -v, --show-nonprinting   use ^ and M- notation, 
			   except for LFD and TAB
      --help     display this help and exit
      --version  output version information and exit

With no FILE, or when FILE is -, read standard input.

Report bugs to <bug-textutils@gnu.org>.

Don’t despair if you prefer a graphical user interface. Konqueror, the default KDE file manager, provides painless and colourful access to the man and Info pages. You may want to try info:info in the Location address bar, and you will get a browsable Info page about the info command. Similarly, man:ls will present you with the man page for the ls command. You even get command name completion: you will see the man pages for all the commands starting with ls in a scroll-down menu. Entering info:/dir in the address location toolbar displays all the Info pages, arranged in utility categories. Excellent Help content, including the Konqueror Handbook. Start up from the menu or by typing the command konqueror in a terminal window, followed by Enter; see the screenshot below.

Figure 2-2. Konqueror as help browser

The Gnome Help Browser is very user friendly as well. You can start it selecting Applications→Help from the Gnome menu, by clicking the lifeguard icon on your desktop or by entering the command gnome-help in a terminal window. The system documentation and man pages are easily browsable with a plain interface.

The big advantage of GUIs for system documentation is that all information is completely interlinked, so you can click through in the SEE ALSO sections and wherever links to other man pages appear, and thus browse and acquire knowledge without interruption for hours at the time.

Some commands don’t have separate documentation, because they are part of another command. cd, exit, logout and pwd are such exceptions. They are part of your shell program and are called shell built-in commands. For information about these, refer to the man or info page of your shell. Most beginning Linux users have a Bash shell. See Section 3.2.3.2 for more about shells.

If you have been changing your original system configuration, it might also be possible that man pages are still there, but not visible because your shell environment has changed. In that case, you will need to check the MANPATH variable. How to do this is explained in Section 7.2.1.2.

Some programs or packages only have a set of instructions or references in the directory /usr/share/doc. See Section 3.3.4 to display.

In the worst case, you may have removed the documentation from your system by accident (hopefully by accident, because it is a very bad idea to do this on purpose). In that case, first try to make sure that there is really nothing appropriate left using a search tool, read on in Section 3.3.3. If so, you may have to re-install the package that contains the command to which the documentation applied, see Section 7.5.

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Linux traditionally operates in text mode or in graphical mode. Since CPU power and RAM are not as expensive as they used to be, every Linux user can afford to work in graphical mode and will usually do so. This does not mean that you don’t have to know about text mode: we will work in the text environment throughout this course, using a terminal window.

Linux encourages its users to acquire knowledge and to become independent. Inevitably, you will have to read a lot of documentation to achieve that goal; that is why, as you will notice, we refer to extra documentation for almost every command, tool and problem listed in this book. The more docs you read, the easier it will become and the faster you will leaf through manuals. Make reading documentation a habit as soon as possible. When you don’t know the answer to a problem, refering to the documentation should become a second nature.

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Most of what we learn is by making mistakes and by seeing how things can go wrong. These exercises are made to get you to read some error messages. The order in which you do these exercises is important.

Don’t forget to use the Bash features on the command line: try to do the exercises typing as few characters as possible!

1. Determine whether you are working in text or in graphical mode.
   I am working in text/graphical mode. (cross out what’s not applicable)
2. Log in with the user name and password you made for yourself during the installation.
3. Log out.
4. Log in again, using a non-existent user name
   → What happens?

Log in again with your user name and password.

1. Change your password into P6p3.aa! and hit the Enter key.
   → What happens?
2. Try again, this time enter a password that is ridiculously easy, like 123 or aaa.
   → What happens?
3. Try again, this time don’t enter a password but just hit the Enter key.
   → What happens?
4. Try the command psswd instead of passwd
   → What happens?

• New password
  • Unless you change your password back again to what it was before this exercise, it will be P6p3.aa!. Change your password after this exercise! Note that some systems might not allow to recycle passwords, i.e. restore the original one within a certain amount of time or a certain amount of password changes, or both.

These are some exercises to help you get the feel.

1. Enter the command cd blah
   → What happens?
2. Enter the command cd ..
   Mind the space between cd and ..! Use the pwd command.
   → What happens?
3. List the directory contents with the ls command.
   → What do you see?
   → What do you think these are?
   → Check using the pwd command.
4. Enter the cd command.
   → What happens?
5. Repeat step 2 two times.
   → What happens?
6. Display the content of this directory.
7. Try the command cd /
   → What happens?
   → To which directories do you have access?
8. Repeat step 4.
   Do you know another possibility to get where you are now?

1. Change directory to / and then to etc. Type ls; if the output is longer than your screen, make the window longer, or try Shift+PageUp and Shift+PageDown.
   The file inittab contains the answer to the first question in this list. Try the file command on it.
   → The file type of my inittab is …..
2. Use the command cat inittab and read the file.
   → What is the default mode (runlevel) of your computer?
   Not every distribution has this file. Ubuntu Edgy Eft doesn’t.
3. Return to your home directory using the cd command.
4. Enter the command file .
   → Does this help to find the meaning of .?
5. Can you look at . using the cat command?
6. Display help for the cat program, using the --help option. Use the option for numbering of output lines to count how many users are listed in the file /etc/passwd.

1. Read man intro
2. Read man ls
3. Read info passwd
4. Enter the apropos pwd command.
5. Try man or info on cd.
   → How would you find out more about cd?
6. Read ls --help and try it out.

Answer Key
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