Linux Tutorial

[WatchOut]

4.3.1 How to switch between text and graphical consoles?
Pressing the key combination <Ctrl><Alt><F1> will switch you to to the first text console at any time. <Ctrl><Alt><F2> will switch you to the second text console, <Ctrl><Alt><F3> to the third text console, etc, up to <Ctrl><Alt><F6>, for the total of 6 text consoles. <Ctrl><Alt><F7> will switch you to the first graphical user interface (GUI) console if one is running. <Ctrl><Alt><F8> to the second GUI console, etc., up to <Ctrl><Alt><F11> for the total of 5 GUI consoles. The 12th console is either used as the 6th GUI (RedHat 6.1) or a place to which kernel messages are continually displayed (Mandrake 7.0, really cool feature). Typically none or only the first GUI console is running.
<Ctrl><Alt><F1> means: "Press the left <Ctrl> and <Alt> keys and hold them. Now press <F1>. Release <F1>. Release <Ctrl> and <Alt> keys."

Thus, sitting at a Linux computer I can have many consoles opened at the same time, and I can switch between them using the hot keys as described above. I have to log in on each console to be able to use it--I may log in as the same user (multiple times), or different users. Each login session is quite separate; they should not interfere with each other (the X sessions sometimes may if you log in as the same user twice). The first 6 consoles are text-based, command-line terminals (CLI, "command line interface") and are named tty1, tty2 ... tty6 (historical name, "tty" stands for "teletypewriter"). The subsequent consoles are graphical (GUI). These are all *local* consoles--my local linux computer is truely muliuser and multitasking.

You can connect to a Linux computer remotely, over a network. While connected, you can have a program run on the remote Linux server and the display sent to your terminal on your "local" console. This local console can be Linux-based or another operating system-based. One cannot run programs remotely on an MS Windows server, but it is often used with Linux. It is really helpful to be able to distinguish if your program is run locally or remotely.

The full-screen text consoles are terminals by themselves. Under the GUI consoles, you can also create "slave" pseudo-terminals (in a window) on demand--they will be called pts0, pts1, ....

Sitting at a text terminal, you can determine the name of your terminal using the following command:

tty

I can determine the computer on which my current session is located using:

uname -a

The name of the command "uname" is derived from "UNIX name". It shows the operating system name, the server name, the version of the operating system kernel, and the time of the compilation of the kernel.

You can close any text terminal by typing "exit" inside it.

The Linux GUI console is quite similar to other GUIs you might have used, e.g., MS Windows, but there are also numerous important differences. I love multiple "desktops" to stay organized--the default setup in KDE offers 4 desktops (it can be customized to between 1 and 16). I run many programs and never close them, so to stay organized I keep a connectivity application (netscape with all its windows, knode newsreader, and licq) together on Desktop2, abiword, staroffice and a text editor on Desktop3, games and konqueror with helpfiles on Desktop4, and leave Desktop1 for the more occassional chores. One can switch between desktops by clicking on the "desktop pager" on the "K-panel" or using <Ctrl><TAB>. To switch between applications on a same desktop, I may click the application window, or click its icon representation on the "applicaton panel", or use <Alt><TAB> to toggle between the applications. <Ctrl><Esc> will give me a list of the processes currently run on the local machine ("localhost").

4.3.2 How do I setup video card, monitor and mouse for the X-server?
This should be set-up during your Linux initial installation unless you skipped the step. To set it up now, you may try, as root, one of these text-mode configurators (as root):
Xconfigurator
XF86Setup
xconf
Under RedHat, you can also run the command setup (as root) and access Xconfigurator from there.
To setup X-windows under Linux, you may need to know your hardware. You may want to dust your monitor manual to see what maximum synchronization frequencies (vertical and horizontal) your monitor supports. The message when the computer boots may give you a clue about what type of video card you have and with how much video memory. Also running these commands will likely provide helpful information:
lspci
SuperProbe

Read the label underneath your mouse to find out about the mouse type. Next time you buy a mouse, get a 3-button "Linux-ready" Logitech or similar (Linux makes good use of all three mouse buttons). A standard (clone or not) mouse always makes a good sense--I would never buy an unusual mouse because it may requires a weird driver or otherwise be a installation/functional pain.

During testing of the X-server, if the screen goes blank, displays funny lines, or otherwise obviously does not function as designed, kill it fast with <Ctrl><Alt><BkSpace> and re-check your monitor sync frequencies. Running too high frequencies can be harmful to your monitor.
If you really have problems, set up a plain vga X server first (resolution 640x480 pixels, 16 or 256 colours). You can fine-tune it later, after you get some understanding of how things work on your system, or perhaps with the help of some nicer setup tools available under X.
After setting up X, you can start it manually using:

startx &

The "&" makes your command run in the background so that your text terminal is not blocked. You could also use:

init 5

which will switch your system to runlevel 5, which means "the graphical user interface run level". To start X automatically (or not, your choice) on the system reboot, read the next few paragraphs.

[WatchOut]

4.3.3 Can I have a GUI login prompt?
To start your X-server automatically on the system start-up and display a graphical login prompt, you have to change (as root) just one character in the file /etc/inittab . This file specifies something like:
id:3:initdefault:
Change it to
id:5:initdefault:
This sets up the default runlevel to 5, which is X-Windows. The meaning of the different runlevels is explained in the same /etc/inittab file :
0 - halt (Do NOT set initdefault to this)
1 - Single user mode
2 - Multiuser, without NFS (The same as 3, if you do not have networking)
3 - Full multiuser mode
4 - unused
5 - X11
6 - reboot (Do NOT set initdefault to this)
You can change the runlevel from the command line. E.g., this command (has to be executed as root):
init 6
will reboot your computer, while the following command would switch your computer to a single-user mode:
init 1

To find out which runlevel I am currently at, I use the command runlevel.

To fine-tune the appearance of my X login screen, I can use (under X):

kcontrol &

and select "System"-"Login Manager". I like a login screen with an analog clock, big font, the login name of the last user already typed in, and the focus pre-set on the password field in the dialog box.

4.3.4 How do I install kde (e.g., on RedHat 5.2)?
This section is only of interest only for those who run an older distribution.
RedHat 5.2 does not install kde by default because at the time of the RH5.2 release there was a problem with the license for a library that the kde uses. Otherwise, kde is a very good GUI, the library license problem is now solved, and the RedHats 6.0 up include kde (alongside the more ornamental GNOME). Still, the kde binaries are on your RedHat 5.2 CDs, you just have to install them yourself. (If you don't have the CDs, you can download the binaries from the kde site on the Internet.)

First check if your X-server works by executing:
xinit
[The X-server is a bare-bone X-windows system, without a "Windows Manager." You can execute your X-windows programs from here by typing the program name (with leading ./ or full path) in the X-terminal window, but you will not be able to move or resize the windows, add icons, etc.]
You can exit your X-server by typing exit in the X-terminal window, or pressing <Ctrl><Alt><Bkspace> to kill the X-windows server. (The last solution is perfect should your windows ever hang-don't reboot in such a case.) If your X-server does not work, see the next answer.
Now, login as root. Mount the RH5.2 CD:
mount /mnt/cdrom
Go to the proper directory:
cd /mnt/cdrom/kde/distribution/RedHat/i386/binary
It is useful to use the command line autocompletion (press Tab) when typing long paths or filenames.
Read the README file:
cat README-2rh51-rpms | more
Use the rpm "RedHat Package Manager" to install the necessary packages
rpm -iv packagename
The packages have filenames ending with .rpm. First install the qt libraries, then kde support, then kde libs, then kde base. If you choose the wrong order, the dependency check will fail and the package will not install (rpm will issue a message). This is not serious, just re-install the required package first, and then try the next package again. After you are done with the base, you may want to install all other packages for kde (util, admin, network, games, graphics, multimedia)--they are not big, so you may consider installing them all. Finally, just to make sure that you installed everything type:
rpm -ivh *.rpm
The options "vh" print some extra info. You will get some messages like "the package is already installed" If there is more than a screenful of them, you can scroll back using <Shift><PgUp>. If you really don't like the command-line-based rpm package manager, you may install the same packages using a GUI front to rpm called glint (available only in RH5.2). Just type "glint" in the X-windows terminal.
Now tell your system that kde is to be your default X-windows manager. In the user home directory, create an .Xclients file:
pico .Xclients
which contains just one line:
/opt/kde/bin/startkde
Type in the line and save the file. (Adjust the line as required so the location of the startkde file is correct.) Now, make the file executable to all users:
chmod a+x .Xclients
Check if the permissions were changed:
ls -l .Xclients
[Files with a dot at the beginning are not displayed by a regular ls command, there are something like hidden files under DOS. You must use its name or ls -a .]
If you created the file as root not the user, change the owner and the group of the file to the proper user:
chown user_name .Xclients
chgrp user_name .Xclients
That's it. Now typing startx should start your X-server with the kde as the windows manager.

[WatchOut]

4.3.5 How can I change my default desktop to KDE (or Gnome or yet another)
In my home directory, I create (or edit if it exists) the file .xsession using my favourite pico editor:
pico .xsession

[Pls note the dot at the beginning of the filename, files with names starting with dots are normally "invisible".]
On my RedHat 6.2 system, the file contains just one line:

exec startkde

KDE clearly works best for me, although it feels heavy on older hardware or under a load. Here is my list of windows managers available on the RedHat or Mandrake installation CD:

startkde (to run kde. on some systems, the command may be kde)
gnome-session (to run Gnome)
xfce (to run XFce, my favourite "lightweight" desktop)
afterstep (to run afterstep)
AnotherLevel (to run AnotherLevel)
fvwm2 (to run fvwm2)
fvwm (to run fvwm)

Of course, the alternative windows manager will run only if it is installed on your system. The above windows managers are available on RH/Mandrake CDs for you to decide if you want to install them. I use almost exclusively KDE, although the other managers may be smaller and faster. Gnome is a famous X-windows project which is said to be more advanced and is prettier than KDE, but it is still quite buggy, so perhaps not recommended unless you don't mind occasional trouble. RH6.x contains both major X-windows systems, Gnome and KDE.

4.3.6 Can I have multiple sessions of X running at the same time?
Yes, you can. When you issue the first startx command on your system, it opens the first X-session on the default display 0. The second X-session must be opened on a different display. For example, this will open a second X-session on the display 1:
startx -- :1
You can have up to 6 concurrent X sessions. Use <Ctrl><Alt><F7> to switch to display 0, <Ctrl><Alt><F8> to second screen, etc. up to <Ctrl><Alt><F12> Try man startx if you need more info.
In a similar fashion, you can open another bare X-server session without a window manager. This will open one on display 2:
xinit -- :2
On this bare-bone X-display I can run a different windows manager (so as to have two different ones running at the same time) by typing in the X-terminal window one of these (see the previous answer for more details):
startkde
gnome-session
xfce
afterstep
AnotherLevel
fvwm2
fvwm
4.3.7 Can my sister have second GUI login prompt so she does not have to kill my X-session to start hers?
To enable several concurrent GUI logins on different local consoles under RedHat (RedHat uses program gdm for graphical logins), I had to edit the file: /etc/X11/gdm/gdm.conf . I have the following entry at the end of this file to enable 4 login terminals <Ctrl><Alt><F7> to <Ctrl><Alt><F10>:
[servers]
3=/usr/bin/X11/X vt10
2=/usr/bin/X11/X vt9
1=/usr/bin/X11/X vt8
0=/usr/bin/X11/X vt7

Having four GUI lets me run KDE and GNOME at the same time on one computer with two GUI terminals spare, so my sister can login despite my having screensavers with password-protection.

To enable several concurrent GUI logins on different local consoles under Mandrake (Mandrake uses kdm for graphical logins), I had to modify two files: /etc/X11/xdm/Xservers to include something like:

:0 local /usr/X11R6/bin/X :0
:1 local /usr/X11R6/bin/X :1
:2 local /usr/X11R6/bin/X :2

and /etc/X11/xdm/xdm-config to copy all the settings for display 0 to display 1 and 2 so that it includes this:

DisplayManager._0.authorize: true
DisplayManager._1.authorize: true
DisplayManager._2.authorize: true
DisplayManager._0.setup: /etc/X11/xdm/Xsetup_0
DisplayManager._0.startup: /etc/X11/xdm/GiveConsole
DisplayManager._0.reset: /etc/X11/xdm/TakeConsole
DisplayManager._1.setup: /etc/X11/xdm/Xsetup_0
DisplayManager._1.startup: /etc/X11/xdm/GiveConsole
DisplayManager._1.reset: /etc/X11/xdm/TakeConsole
DisplayManager._2.setup: /etc/X11/xdm/Xsetup_0
DisplayManager._2.startup: /etc/X11/xdm/GiveConsole
DisplayManager._2.reset: /etc/X11/xdm/TakeConsole

This enables me to run gnome and kde at the same time on a single computer with the third GUI terminal spare.

[WatchOut]

4.3.8 How to X-window remotely?
- Start X-server on the local machine, e.g.
xinit
- From the x-terminal give the remote machine the permission to display on your local screen:
xhost name_of_the_remote_server
In the really secure environment of my house, I could even give all servers the permission to display on my screen using (don't do it when connnected to the Internet):
xhost +
- Telnet the remote server.
- Start an X-program on the remote server directing the display on your local screen, for example, you may start a window manager:
startkde -display local_machine_name:0.0 &
The symbol "&" puts the command in the background, so that your telnet window is still available to you.
The 0.0 means "display zero, screen 0", which is your first screen on the first display and makes sense since you can have many concurrent sessions of X running on your computer with Linux.
You don't have to specify the "-display" option if your environment variable DISPLAY specifies the correct location on your current terminal, which is the case on my systems by default, but not on everybody else's as I am told. You can check your DISPLAY setting using:
echo $DISPLAY
- After I finish my remote X session, I restore the access control to my X-server using:
xhost -name_of_the_remote_server
or
xhost -
Example. This sequence of commands will run Netscape on the remote machine called marie, directing the display to the X-server with X-windows manager which runs on the local machine hacker:
startx
xhost marie
telnet marie
[login]
netscape -display hacker:0.0 &
[do my stuff]
[logout]
xhost -marie
In principle, you can run a program on any computer on the network, and display the output on any other (not necessarily the one you are sitting at).
I use remote X-windowing a lot to run fat programs (kde, Word Perfect 8, and Netscape) on a slim machine (486-33, 8 MB mem) which would not be able to run those by itself. It is also a convenient and fast way to work with files on a remote system for which the nfs mount is not set up.
X-windows was designed to run remotely over the network. Remote X-windowing is a very powerful tool, on top of being quite a pleasant experience. Try it out.

You can even run a program on a remote Linux (or any Unix) computer and redirect the display to a local MS Windows machine if you install an X-windowing program for MS Windows. For a good overview of choices, see: <b> linuxworld.com/linuxworld/lw-2000-09/lw-09-legacy_1.html </b>

4.3.9 How do I install TrueType fonts from my MS Windows partition?
Some distributions come with a TrueType font server but no (or a limited choice of) TrueType fonts. You can install your own TrueType fonts though. Here is how I did it manually. Mandrake includes a GUI utility to transfer you MS Windows fonts to Linux, so you don't have to bother with the procedure below.
0. From under K-menu (KDE), select "System"-"Font Manager" (or equivalent) and note what fonts you have installed.

1. On the command line, check if the "free type" font server is installed:

rpm -q freetype

This queries (option "q") the rpm package manager for the package "freetype". If the package is installed, go to next step. If "freetype" is not installed, install it now from your distribution CD. "freetype" was installed on my system after a "full" RH installation.

2. As root, make a directory that is to hold your TrueType fonts:

cd /usr/X11R6/lib/X11/fonts
mkdir TrueType

This directory is referred to in the configuration file /etc/X11/XF86Config so make sure that the name of the directory is exactly as shown. If you would like to name the directory differently, you have to edit /etc/X11/XF86Config and make appropriate adjustments. My "default installation" RedHat contained such a line:

FontPath "/usr/X11R6/lib/X11/fonts/TrueType"

3. As root, copy your *.ttf files from the original location to the TrueType font directory that you just created. I took some TrueType from my MS Windows partition, you may need to use a different source location:

cd /usr/X11R6/lib/X11/fonts/TrueType
cp /mnt/dos_hda1/windows/fonts/my_private_fonts/*.ttf .

Before copying any fonts, make sure that it does not violate your licence agreement.

4. As root, run the following commands:

cd /usr/X11R6/lib/X11/fonts/TrueType
ttmkfdir > fonts.dir
cp fonts.dir fonts.scale

5. Close all X-windows applications and log out from X-windows.

6. As root, restart your X-font server (or reboot your computer):

/etc/rc.d/init.d/xfs stop
/etc/rc.d/init.d/xfs start

7. Log back onto your KDE, and from under K-menu, select "System"-"Font Manager" to see if the fonts installed correctly.

This parts is based on: <b>computerbits.com/archive/20001000/linux0010.htm</b>

[WatchOut]

4.3.10 How do I copy-paste?
Under X-windows, use your mouse: highlight the text to be copied, switch to the location where to copy, and press the middle mouse button to paste. This works nice and fast, as long as during the switching you don't disselect the original text. If your mouse has only two buttons (no middle button), use "both buttons together" or perhaps the right button (which combination works depends on your setup). This is the traditional "X-Windows style" copying.
Many GUI applications (but not all) also support the Mac/MS-Windows-style "copy-paste": Select the text. Use the menu item "edit"-"copy" (either from the pull-down menu, or a local menu activated with the <RightMouseButton>). Switch to the location where to copy to. Use the menu item "edit"-"paste". This works fine for applications which use the same toolkit (e.g. KDE or GNOME) but does not always work across toolkits (e.g., from a GNOME application to the KDE application).

As a keyboard shortcut for the last method, I can use <Ctrl><c> for copying the highlighted text and <Ctrl><v> for pasting. Text can be highlighted without mouse using <Ctrl><Shift><RightArrow>.

You may also use the cut-paste history. Try running klipper (in X-terminal, KDE).

The two copying methods are supposed to be separate; therefore, they should not mutually interfere.

To capture the content of a window or the entire screen to a graphics file, I use knapshot. Alternatively, I can use <Alt><PrintScreen> to take a snapshot of the current window into the clipboard, and <Ctrl><Alt><PrintScreen> to take a snapshot of the entire desktop into the clipboard.

To catch contents of a text console (outside of the GUI console), I could use in X terminal (probably as root):

cat /dev/vcs1

and then copy and paste whatever I need from the X terminal with a mouse. I need to adjust the number in "vcs1" if my terminal to capture is not terminal 1.

The text-based consoles support the mouse if you run the gpm daemon. Type gpm to test it--it will run fine if your mouse is appropriately configured. (You may want to run mouseconfig to configure your mouse.) To have gpm start automatically on the system startup and stay running, select the gpm daemon using the ntsysv utility. Use gpm exactly the same as the GUI cut-paste: highlight the text to be copied, move the text cursor to the "copy to" location, and then press the middle mouse button (or both buttons at once for a two-button mouse) to paste.

4.3.11 How do I Display and Control a Remote Desktop using VNC
(VNC = Virtual Network Computing). A very useful application--don't miss it.
VNC is a cross-platform utility that allows me to display a remote graphical desktop over a standard network connection. For example, I can use VNC on an MS Windows PC to display an X-window environment of my mighty Linux server downstairs, or the other way around. VNC will even run over a 56k modem networking, but probably only for fun or in emergency (too slow a connection for normal work).

Recent Mandrake or RH will have vnc on their distributions CD. The MS Windows version you have to download yourself. See <b>uk.research.att.com/vnc/</b> for download information and more details.

On Linux, VNC consists of four commands: vncserver, vncviewer, vncpasswd, and vncconnect. I typically need just two of them: vncserver and vncviewer. A brief description of the commands follows.

vncserver
The server that has to be running on the host (remote) computer. You start the server as the user whose desktop will be displayed (don't run the server as root or somebody else somebody may kidnap your computer!).

vncviewer
The local application wich connects to the vncserver and displays the remote environment. You need to know the password and ip address of the server to connect.

vncpasswd
Password selection utility for vncserver. The server won't run without password (good behaviour). Therefore, if you don't select one, it will prompt you. Hence, I don't need to explicitly run vncpasswd.

vncconnect
Tells vncserver to connect to a listening VNC viewer on the given computer and port. This way I can avoid giving anybody a password.

Xvnc
A "master" program that I don't really need to run directly (vncserver and vncviewer are scripts which call Xvnc).

For a list of all available options I run:
Xvnc -help

It is not recommenced to run the VNC server as root due to potential security issues. If you need root privileges, login as a user and then execute su

Two examples of "typical" sessions follow.

Example 1. Sitting at an MS Window computer, I can display an X environment from my Linux server, using the following sequence:

[start a DOS terminal and type in the following command]
telnet my_linux_server_name
[log in to your user account on Linux and type in it the following command]
vncserver
[provide a really good password of your choice when prompted; mine was "357+Simon&Garfunkel"]
[re-enter the same password for confirmation]
[watch the messages and note the screen number on which the server is started; mine was ":4"]
[From the "Start" menu on the MS Windows computer, select "Programs" - "Vnc" - "Run VncViewer"
[in the input box that appears, type the server ip address and screen number as shown on the next line]
my_linux_server_ip_address:4
[in the input box that appears type the password as follows]
357+Simon&Garfunkel
[an X-windows desktop should now appear on top of your MS Windows desktop]
[do your work as you normally would in Xwindows]
[when done, switch to the telnet session window and type in it the following two commands]
vncserver - kill :4
logout

Example 2. Sitting at my Linux X desktop, I can display and remotely control an MS Windows computer screen. Hopefully, nobody else is using this MS Windows computer at the same time, because I move its mouse pointer.

[Walk to the MS Windows computer because you probably cannot telnet it]
[From the "Start" menu, select "Programs" - "Vnc" - "Run WinVnc (app mode)"
[From the "System Tray", click the mouse right button on the "Vnc" icon, and select "Properties"]
[In the dialog box that appears, fill in the password. Leave the screen number on "auto".]
[Walk back to your Linux desktop]
[Start an X terminal and type in it]
vncviewer ms_windows_server_name_or_ip
[When prompted, type in the password]
[a MS Windows desktop should now appear on top of your X]
[do your work as you normally would on MS Windows]
[When done, right click on the Vnc icon in the system tray and select "Close VNC".]

[WatchOut]

4.4.1 How to setup my soundcard?
Try to run (as root)

sndconfig

Unless you have a very fancy sound card, this will work for you. At the end of the setup, Linus says how he pronounces "Linux". (On RedHat, "sndconfig" can be also run via the "setup" utility--type setup . )
You may want to try your soundcard and cdrom using a command line cdplayer. Put a music CD to your CDROM and type:

cdplay

If this does not work, maybe you don't have /dev/cdrom? Check if you can mount a data CD as root (look here) and create the device /dev/cdrom by linking it to the appropriate drive (most likely /dev/hdb), for example (as root):

ln -s /dev/hdb /dev/cdrom

If cdplay works for root, but does not work for a regular user, you may need to give (as root) everybody the permissions to read and write to the the file /dev/cdrom or review the permissions on /mnt/cdrom, or modify /etc/fstab as explained earlier, e.g.:

chmod 666 /dev/cdrom

(The directory /dev is where all your devices appear as files.)
To play third song, try:

cdplay play 3

You can also use the command cdp for rudimentary command line interface to cdplay, but perhaps you prefer the interfaces available from under X-windows (e.g., from KDE "K" menu, choose: Multimedia-"CD Player").

To stop the music either press the button on your CDROM or issue one of these commands:

eject
cdplay stop
Troubleshooting. If you are having problems with a sound card, a manual configuration is an option. Here is my setup for a SoundBlaster16-compatibile ("no name") soundcard that persistently played at half speed (too slow and with "low voice") because it was misdetected. The resource to read turned out to be: /usr/src/linux-xxx/Documentation/sound (hope you installed the kernel source code so that you have the documentation). The file to edit is /etc/modules.conf. The critical line in this file (after manual edition) is:

options sb esstype=1688 io=0x220 irq=5 dma=0 dma16=5 mpu_io=0x330

The change that I had to make was to insert the "esstype=" option. After modification, the best to test your setup is to cold reboot (shutdown to a halt, and then recycle the power).

4.4.2 How do I setup my printer?

Start an X-terminal (perhaps by pressing the proper button) and type in it (as root or you will be prompted for the root password):

printtool &

This program does a complete printer setup, you just have to fill up the information about your type of printer and where it is hooked up.

Specifying the proper printer port is the most important part. If you don't know which one is yours try: on RedHat 5.2: lp1 (this is the first parallel port on RH5.2 ) or lp2 (this is the second parallel port on RH5.2) or lp3 (this is the third parallel port on RH5.2); on RedHat 6.0 (or later): lp0 (this is the first parallel port on RH6.x) or lp1 (this is the second parallel port on RH6.x) or lp2 (this is the third parallel port on RH6.x). After upgrading from RH5.2 to 6.0, the printing stopped working because the name of the parallel ports changed. I had to re-run the printool and adjust the port. The numbering of ports changed to bring it in line with numbering of other devices, which always starts from 0.

Try printing an ASCII test-page straight to the port. Only when this works set up the bells and whistles.

If you are setting up a remote printer, make sure that your machine has the permission to use the remote printer. The permissions are set in the file /etc/hosts.lpd (more secure) or /etc/hosts.equiv (less secure) on the machine to which the printer is attached. These files simply list the names of the remote computers that can use a local printer, one computer name per line. Mine looks like this:

hacker
mars

The file /etc/hosts.lpd did not exist on my system, so I created it.
For quick information about the printers on your machine, you may want to view the file /etc/printcap :

cd /etc/
cat printcap

Here is the meaning of some codes that I see in my /etc/printcap:

: Field separator (separates the entries in the file).
\ (at the end of line) Continuation on the next line.
lp Name of the printer. "lp" is the name of the default printer on your machine. Subsequent printers are often, by default, given the the names lp0 or lp1, ... (or whatever you like) but this should not be confused with the name of the devices (parallel ports) to which they are connected.
sd=/var/spool/lpd/lp My spool directory (sd).
mx#0 Maximum size of print jobs (mx) in blocks. "0" means no limit.
sh I want headers to be suppressed (sh). Header is the page with your name that prints before your printing job (waste of paper if you print at home).
rm=mars Name of the remote machine (rm), which on my system is called "mars (my printer is connected to a different computer).
rp=lp
or

lp=/dev/lp0
Name of the remote printer (rp), which is the name of the printer on the remote machine ("lp" on "mars" on my home network)
or
the name of the device on the local machine. "/dev/lp0" is the first parallel port on RH6.x (it used to be /dev/lp1 on RH5.2, the numbering of parallel ports changed).

if=/var/spool/lpd/lp/filter Input filter (if). Your printing job will be formatted by this "filter" before it is sent to the printer.
sf Suppress the form feed (sf) that is normally sent when printing is completed (use it if your printer keeps printing an empty page at the end of each jobs).

The printer is controlled using the command lpc (as root). Type "?" to see the options. This program is notorious for its peculiarities, so don't get discouraged easily. The printer queue can be viewed with lpq and cleaned up with lprm , both of which work for a user (not only root). You can print from the command line using the command lpr. Under KDE, you can control the printer queue from the program available under the "K-button"-"Utilities"-"Printer Queue".
Most printers will work perfectly under Linux, but some may not utilize their full capablity due to lack of information/drivers from the vendors. Therefore, when purchasing a new printer, you may want to consult the database of Linux printers: <b>linuxprinting.org/database.html</b>. In brief, it is a good bet is to select ( <b>linuxprinting.org/suggested.html </b>):

- For inexpensive colour printing: an Epson Stylus, for example: Stylus C80 (better) or Stylus C60 (cheaper) (Dec.2001). HP inkjets are generally less recommended than Epson's. Please note that "inkjet-type" printers are (in general) "not-so-great" for black-and-white printing. Also, they are meant to be "personal" printers and do not handle well high volumes. Yet they can offer excellent colour output, particularly on good quality paper. Kids love inkjets.
- For low-end laser printing: a Lexmark or Brother printer. Many Hewlett-Packard (HP) laser printers will also work perfectly, but one has to be more careful when selecting an HP printer due to their more limited support. Lower-cost laser printers are always black-and-white, but they offer excellent quality text printouts. You may avoid some headaches if you select a printer which supports "Postscript".

[WatchOut]

4.4.3 Word Perfect 8 does not have a driver for my printer
If you installed your printer in KDE using the printtool and it had a driver which works fine, set up Word Perfect to print using the "passthru postscript" driver.
4.4 4 Where are the setup and configuration files?
System-wide settings settings are stored in the /etc directory. User-specific settings are stored in the user home directory /home/user_login_name.
Here is a listing of some system-wide configuration files that I use most often:

SHELL DEFAULTS
/etc/bashrc - system-wide default functions and aliases for the bash shell
/etc/profile - system-wide defaults for bash shell, including system-wide environment variables.

ADMINISTRATIVE SETTINGS
/etc/passwd - contains passwords and other information concerning users who are registered to use the system. It can be modified by root directly, but it is preferable to use a configuration utility such as passwd to make the changes. A corrupt /etc/passwd file can easily render a Linux box unusable.
/etc/shadow - contains "shadow" information for the passwd file, i.e., the information pieces which "the world" does not have permission to read.
/etc/group - similar to /etc/passwd but for groups.
/etc/crontab - setup for "cron", which runs commands periodically (hourly, daily, weekly, monthly, etc.).
/etc/inittab - runs different programs and processes on startup.
/etc/issue - message that accompanies login prompt. This is often overwitten by the rc.local script.
/etc/issue.net - same as above, but used when login is attempted over the network.
/etc/motd - "message of the day" file, displayed after a user logs in.
/etc/rc.d/rc.local - the last script to execute on the system bootup. I put the commands which customize my local machine at the end of this file. It works like DOS "autoexec.bat".

NETWORK CONFIGURATION
/etc/hosts - contains a list of host names and absolute IP addresses.
/etc/hosts.allow - hosts allowed to access Internet services
/etc/hosts.deny - hosts forbidden to access Internet services
/etc/resolv.conf - setups for a list of domain name servers used by the local machine
/etc/inetd.conf - configures the inetd daemon to tell it what TCP/IP services your machine should run.
/etc/exports - specifies hosts to which file systems can be exported using NFS (network file system). man exports contains information on how to set up this file for remote users.

HARDWARE CONFIGURATION
/etc/conf.modules - setup for the linux kernel modules. Modules are like "device drivers" under MS Windows or DOS.
/etc/fstab - contains information on partitions and filesystems used by system to mount different partitions and devices on the directory tree.
/etc/mtab - shows currently mounted devices and partitions and their status.
/etc/lilo.conf - configuration file for lilo boot loader.
/boot/grub/grub.conf - configuration file for grub boot loader.
/etc/printcap - setup for printers.
/etc/termcap - ASCII database defining the capabilities and characteristics of different consoles, terminals, and printers. You typically don't want to change these.
/etc/X11/XF86Config - X configuration file. For XFree version 4.xx, the file is /etc/X11/XF86Config-4 (if it does not exist, then XF86Config is tried).

4.4.5 What are all the device files?
Devices appear as files in the directory /dev. They can be read, or written to, if you have the permission to do so. The listing of the file reveals some important details about the device, for example:
ls -l /dev/ttyS3

on my system produces the following output:

crwxr-xr-x 1 root tty 4, 67 Mar 13 22:59 ttyS3

The initial "c" indicates a character device. "b" would mean "block device", "p"=FIFO device, "u"=unbuffered character device, "d"=directory, "l"=symbolic link. The numbers "4, 67" mean that the device major number is 4 and the minor number is 67. To make some devices usable to all users on your system, you may need to set the proper permissions. For example:
ls -l /dev/usb/scanner0
chmod 666 /dev/usb/scanner0

Here is a list of some common devices:

/dev/ttyS0 - the first serial port. The mouse is typically connected here.
/dev/ttyS1 - the second serial port. This may well be the device to which your modem is connected.
/dev/ttyS2 and /dev/ttyS3 the third and fourth serial port (typically not present, but your internal modem may well be configured as one of these).
/dev/modem - the serial modem. In the typical case, a symbolic link to /dev/ttyS1, /dev/ttyS2, /dev/ttyS3 or /dev/ttyS0, depending to which serial port your modem is connected.
/dev/mouse - mouse. In the typical case, a symbolic link to /dev/ttyS0 or similar (see above), depending to which serial port your mouse is connected.
/dev/lp0 - printer on the first parallel port. That's where normally printers are connected.
/dev/lp1 - printer on the second parallel port (typically not present).
/dev/fd0 - first floppy disk drive (almost always present).
/dev/fd0H1440 - driver for the first floppy drive in the high-density mode (1440 kB). Generally, this (or a driver with a device with a similar descriptive name) is invoked when formatting a floppy drive to a particular density. Slackware also comes with drivers that allow for formatting a 3.5" diskette with up to 1.7MB of space. Red Hat and Mandrake do not contain these device drivers files by default.
/dev/fd1 - second floppy disk drive.
/dev/hda - first IDE hard drive (whole drive). Most hard drives on IBM-compatibile PCs are IDE.
/dev/hdb - second IDE hard drive (whole drive). On many computers, the IDE cdrom drive is attached here.
/dev/hdc - third IDE drive (whole drive). On many computers, the IDE cdrom drive is attached here.
/dev/cdrom - a symbolic link to the appropriate drive interface, typically /dev/hdc or /dev/hdb (a CDROM) or /dev/scd0 (a CD-R/RW writer).
/dev/hda1 - the first partition on the first IDE hard drive. /dev/hda2 is the second partion on the first IDE hard drive. As one could guess, /dev/hdd8 would be the eight partition on the fourth IDE hard drive.
/dev/tty1 - the first text console. /dev/tty2 is the second text console, etc.
/dev/dsp - digital audio, i.e., the sound card. "dsp" stands for "digital signal processing".
/dev/sndstat - do cat /dev/sndstat to learn about the status of your sound devices.
/dev/null - used when you want to send output into oblivion.
/dev/random - used to read pseudo-random numbers. Do cat /dev/random to display garbage-looking characters on your screen. There is also /dev/urandom to generate lower-quality random sequences.
/dev/sda -the first SCSI drive (whole drive). On a home machine, you are unlikely to have any SCSI drives (expensive).
/dev/sdb - the second scsi drive ("sdc" is the third scsi drive, etc. There can be many scsi drive on a system).
/dev/sda1 - the first partition on the first scsi drive.
/dev/sr0 - the first scsi CD drive (sometimes called /dev/scd0). If you have an ATAPI CD writer, it will also be likely here.
/dev/sr1-is the second scsi CD drive (sometimes called /dev/scd1), (/dev/sr2 is the third scsi CD drive, etc. There can be many scsi CD drives on the system).
/dev/usb/scanner0 - a usb scanner. Try: less /usr/src/linux/Documentation/usb/scanner.txt for an info on scanner configuration from scratch.

For more info try:
less /usr/src/linux/Documentation/devices.txt
man MAKEDEV

As explained in /usr/src/linux/Documentation/devices.txt, I may need to create some symbolic links to device files locally to configure my system. This is merely a tabulation of existing practice, and does not constitute a recommendation. However, if the links exist, they should have the following uses:

/dev/mouse Current mouse port***
/dev/tape Current tape device
/dev/cdrom Current CD-ROM device***
/dev/cdwriter Current CD-writer device (but my RedHat have /dev/cdrecorder)
/dev/scanner Current scanner device
/dev/modem Current dialout (modem) port***
/dev/root Current root filesystem
/dev/swap Current swap device

The *** mark the symbolic links that are surely present on my Mandrake system. For example, if having problems with mouse I would do something like (as root):
ls -l /dev/mouse
[see if the mouse device is present and where it points]
ln -s /dev/ttyS0 /dev/mouse
[create a symbolic link so that /dev/mouse point to the first serial port]

For SCSI (and ATAPI) devices, /dev/tape and /dev/cdrom should point to the ``cooked'' devices (/dev/st* and /dev/sr*, respectively), whereas /dev/cdwriter and /dev/scanner should point to the appropriate generic SCSI devices (/dev/sg*).

Non-transient sockets and named pipes may exist in /dev. Common entries are:
/dev/printer socket lpd local socket
/dev/log socket syslog local socket
/dev/gpmdata socket gpm mouse multiplexer

[WatchOut]

Some Linux daemons
Daemons are "resident"programs that periodically wake up, check your system and may perform certain functions. They do not take any input and don't normally produce any output. Your Linux system is likely set to run quite a number of daemons. Most of them can be (dis)selected by running the program ntsysv (RedHat) as root and checking the appropriate box. The short description of each daemon is available under netsysv by pressing <F1>. If the daemon you need is not listed in ntsysv, you need to insert your RedHat/Mandrake installation CD and install the appropriate package. The alternative to ntsysv may be tksysv (type as root, in X terminal), which is perhaps more flexible, but way more complicated (it lets you set up the list of daemons to run in each runlevel). Another, simpler and even more powerful+flexible+difficult-to-use tool is /sbin/chkconfig.
Here is a short list of popular daemons with a brief description:

anacron - checks `cron' jobs that were left out due to down time and executes them. Useful if you have cron jobs scheduled but don't run your machine all the time--anacron will detect that during bootup.
amd - automount daemon (automatically mounts removable media).
apmd - Advanced Power Management BIOS daemon. For use on machines, especially laptops, that support apm.
arpwatch - keeps watch for ethernet/ip address pairings.
atd - runs jobs queued by the "at" command.
autofs - control the operation of automount daemons (competition to amd).
bootparamd - server process that provides information to diskless clients necessary for booting.
crond - automatic task scheduler. Manages the execution of tasks that are executed at regular but infrequent intervals, such as rotating log files, cleaning up /tmp directories, etc.
cupsd - the Common UNIX Printing System (CUPS) daemon. CUPS is an advanced printer spooling system which allows setting of printer options and automatic availability of a printer configured on one server in the whole network. The default printing system of Linux Mandrake.
dhcpd - implements the Dynamic Host Configuration Protocol (DHCP) and the Internet Bootstrap Protocol (BOOTP).
gated - routing daemon that handles multiple routing protocols and replaces routed and egpup.
gpm - useful mouse server for applications running on the Linux text console.
httpd - daemon for the Apache webserver.
inetd - listens for service requests on network connections, particularly dial-in services. This daemon can automatically load and unload other daemons (ftpd, telnetd, etc.), thereby economizing on system resources. Newer systems use xinetd instead.
isdn4linux - for users of ISDN cards.
kerneld - automatically loads and unloads kernel modules.
klogd - the daemon that intercepts and displays/logs the kernel messages depending on the priority level of the messages. The priority is (copied from /usr/include/linux/kernel.h ):
KERN_EMERG "<0>" system is unusable
KERN_ALERT "<1>" action must be taken immediately
KERN_CRIT "<2>" critical conditions
KERN_ERR "<3>" error conditions
KERN_WARNING "<4>" warning condition
KERN_NOTICE "<5>" normal but significant condition
KERN_INFO "<6>" informational
KERN_DEBUG "<7>" debug-level messages
The messages typically go to the appropriately named files in the directory /var/log/kernel.

kudzu - detects and configures new or changed hardware during boot.
keytable - loads selected keyboard map.
linuxconf - the linuxconf configuration tool. The automated part is run if you want linuxconf to perform various tasks at boottime to maintain the system configuration.
lpd - printing daemon.
mcserv - server program for the Midnight Commander networking file system. It provides access to the host file system to clients running the Midnight file system (currently, only the Midnight Commander file manager). If the program is run as root the program will try to get a reserved port otherwise it will use 9876 as the port. If the system has a portmapper running, then the port will be registered with the portmapper and thus clients will automatically connect to the right port. If the system does not have a portmapper, then a port should be manually specified with the -p option (see below).
named - the Internet Domain Name Server (DNS) daemon.
netfs - network filesystem mounter. Used for mounting nfs, smb and ncp shares on boot.
network -activates all network interfaces at boot time by calling scripts in /etc/sysconfig/network-scripts .
nfsd - used for exporting nfs shares when requested by remote systems.
nfslock - starts and stops nfs file locking service.
numlock - locks numlock key at init runlevel change.
pcmcia - generic services for pcmcia cards in laptops.
portmap - needed for Remote Procedure Calls. Most likely, you need it for running network.
postfix - mail transport agent which is a replacement for sendmail. Now the default on desktop installations of Mandrake (RedHat uses sendmail instead).
random - saves and restores the "entropy" pool for higher quality random number generation.
routed - daemon that manages routing tables.
rstatd - kernel statistics server.
rusersd, rwalld - identification of users and "wall" messaging services for remote users.
rwhod - server which maintains the database used by the rwho(1) and ruptime(1) programs. Its operation depends on the ability to broadcast messages on a network.
sendmail - mail transfer agent. This is the agent that comes with Red Hat.
smbd - the SAMBA (or smb) daemon, a network connectivity services to MS Windows computers on your network (hard drive sharing, printers, etc).
squid - An http proxy with caching. Proxies relay requests from clients to the outside world, and return the results. You would use this particular proxy if you wanted to use your linux computer as a gateway to the Internet for other computer on your network. Another (and probably safer at home) way to do it, is to set up masquarading.
syslogd - manages system activity logging. The configuration file is /etc/syslog.conf .
smtpd - Simple Mail Transfer Protocol, designed for the exchange of electronic mail messages. Several daemons that support SMTP are available, including sendmail, smtpd, rsmtpd, qmail, zmail, etc.
usb - daemon for devices on Universal Serial Bus.
xfs - X font server.
xntpd - finds the server for a NIS domain and stores the information about it in a binding file.
ypbind - NIS binder. Needed if computer is part of Network Information Service domain.

[WatchOut]

4.5.1 Would it be worth it to set up my home network?
This is an excellent idea. It will let you use the machines that are in your closet now because they were not powerful enough to run standalone. The benefits include sharing hard drives, zipdrives, CDROMs, modem, printers, even soundcards, running programs remotely (the text or graphics mode), browsing the Internet on all computers at the same time over one phone connection. If you ever lose control of your machine, you may also be able to shut it down remotely and thus avoid possible problems--see the answer on shutting down for details.
4.5.2 How to set up my home network?
Hardware. Your hardware must be set up properly. Your network card should have been set up during the initial RedHat installation. If you added your card later, chances are it was autodetected and configured during a subsequent bootup (by kudzu). If it wasn't, you may want to set up your network card now. If you have more than one network card on your computer, you will also need to set up the second cards manually, since Linux will autodetect only 1 network card.
Under Linux, most drivers for network cards are implemented as modules. So setting up a card manually involves just inserting the proper module with its parameters. You don't need to recompile the kernel, nor even reboot your computer (unless you have an uncommon card). To figure out what module(s) and parameters you need, you may want to consult the documentations that comes with the kernel source code:
less /usr/src/linux-2.4/Documentation/networking/net-modules.txt

If needed, you can list all the modules available for your kernel using something like:

modprobe -l | more

If you need more help, see the Linux Network Administrator Guide (file/usr/share/doc/LDP/nag on your system or check tldp.org/LDP/nag/). This excellent guide is known as nag.

There are many ways of inserting a module into a kernel. For a network card, the simplest is to start, as root, netconf and specify the module name there. An alternative is to start an X-terminal, execute "su" (to make yourself a root) and then run /usr/bin/kernelcfg
In most cases, you don't have to specify the parameters (IRQ and address) for your module--the module will know what they should be. However, the parameters were a problem during my setup of two network cards on one computer--you must make sure that you don't have any hardware conflicts. A common source of problems is that the card wants to configure on IRQ 5, which is occupied by the SoundBlaster, or IRQ 3 which conflicts with the second serial port (COM2, cua1, ttyS1). Inspecting the files /proc/interrupts, /proc/ioport and reading bootup messages may help.

For example, my WD8013 card (same as SMC Elite and SMC Elite plus, according to nag) runs under IRQ 10 (set by a jumper on the card and I specified the IRQ in the kernel module setup), under the address 0x300 and uses the "WD" module. My "SMC EtherEZ" card (no jumper settings on the card) runs under IRQ 9, address 0x240 and uses "SMC EtherEZ" module. Please make sure you don't omit the leading "0x" in the address--it means "hexadecimal" and must be there else the number will be interpreted as decimal.
After the module is inserted, you may want to inspect the file /proc/modules to see if the module is indeed loaded (or run lsmod as root). The module configuration file is /etc/modules.conf so if you encounter difficulties (for example, I had difficulty removing modules inserted by mistake), just edit and adjust this file manually, e.g., using pico.
Network configuration. After setting up the network cards and connecting the cables, set up the network by running (as root):
netconf
This program has help! netconf can also be run under GUI, but I did not really try it. If you need more understanding of how networking works, you may want to read the previously mentioned nag. Also, reading this material may be of help: [url]http://ieee.uow.edu.au/~mjp16/wylug-netlinux/notes.html.
It also contains very clear examples on how to set up a small office network that, like our home setup, has only part-time connection to the outside world.
How and what to fill up in netconf depends on your network. You surely want to fill up "Basic Host Information" (enable the first ethernet interface, eth0, fill in the name, aliases and IP number of your local computer) and the "Information About Other Hosts" (names, aliases and IPs of other computers on your home network). This information goes to the files: /etc/hosts and /etc/sysconfig/network, so you may want to inspect these files and adjust them manually.

When setting up the network, don't mess up with the "loopback driver" which has the IP 127.0.0.1. It is always there--it is the IP through which the computer talks to itself.
If you don't have an IP address (as will typically be the case for a home network with no permanent connection to the outside world), you may want to invent one. It does not matter very much what it is since when connecting to the outside world by your modem, you will be dynamically allocated an IP address (a machine can have many IP addresses at the same time). Your invented IP must be formally correct and the net mask must match the class of the network (class A, B or C). See the chapter on IP addresses in the already mentioned Network Administrator Guide (nag) (/usr/doc/LPD/nag on your system, or if you don't have it, download it now from [url]http://metalab.unc.edu/mdw/index.html#guide.
For a home network, you might want to invent a class C network (up to 254 machines, the smallest) IP number which has the first three digits between 192 to 223. The last three digits identify the machine on your class C network and must be between 1 and 254 (don't use 0, it means "whole network" or 255 which is the "broadcast address"). The middle two sets of digits can be anything from 0 to 255. Thus 223.223.223.1 is the first machine on the class C network 223.223.223.0 (the last zero signifies the whole network), with the broadcast address 223.223.223.255. The network mask for a class C network is always 255.255.255.0 (unless you subdivide your network into smaller "subnet", which is not discussed here).
Rather than completely inventing an IP number, it might be safer/better to use one of the numbers reserved for "private networks". For me, the IP number 192.168.1.1 works just fine. This way, your "invented" IP address is guaranteed never to interfere with any IP that may exist in the world.

Typically, the first machine on a network is the one that is expected to have the connection to the outside world (since it was connected first, but there is no standard for that). So, I filled up the GATEWAY to xxx.xxx.xxx.1 (my first machine) on all machines, except for the machine xxx.xxx.xxx.1, where I left this field blank. Actually, although I left the field blank, netconf inserted the gateway 0.0.0.0 into the /etc/sysconf file. This was a source of an annoying error message during the loading of the network card on the bootup. To get rid of the message, I edited /etc/sysconfig/network and set it to something like this:
GATEWAYDEV=
GATEWAY=
[You don't want a gateway on your ethernet interface on this machine if it does not lead to the outside world. The ppp interface on this first machine will be set up as a default gateway once you connect through your modem, e.g. using kppp.]
The name of a computer is entirely arbitrary--the main user normally chooses a short word s/he likes. The domain name of the home network is also entirely arbitrary, unless you have a permanent connection in which case a domain name is registered to you. Try to invent something that does not exist yet--it could make your life easier once you have a permanent connection.
As for the DNS (domain name server, also called "named" = name daemon), RedHat 5.2 and 6.0 comes with DNS preinstalled as "caching-only" so it is easy to configure as such. You may also choose not to use local DNS at all--if your local DNS is looking up an "outside" server and can't find it, it can be a real show-stopper (the machine can appear to be hanged for up to a few minutes). To use local DNS, the "named" service must be enabled-- check this by running setup. To set up the caching-only DNS, fill up the appropriate boxes in netconf. E.g., I filled "nameserver 1" to my first machine on all computers (I entered the loopback address 127.0.0.1 on the machine xxx.xxx.xxx.1, and the proper xxx.xxx.xxx.1 address on all other machines).

[WatchOut]

No routes to other networks and hosts were required in my network, since I don't have other local networks. So I left this field blank.
Other than setting up the hardware correctly and filling up the info under netconf on each computer, as described above, I did not have to do anything on the standard RedHat to get my network working.
Reboot all computers one by one in any order (this is not necessary, but won't hurt you) and watch the boot messages (if they scroll too fast off screen, use <Shift><PgUp> to scroll up, or use dmesg from the command line to view them later). Did your cards configure correctly? Use the command route (as root) to see if the eth0 interface is running. Use the ping command to test the connections between individual machines. Try to telnet your local computer to see it the loopback-only (lo) interface works:
telnet name_of_the_machine_you_are_sitting_at
After a successful login, you can exit the telnet session by typing
exit
Finally, try to telnet another computer on your network:
telnet name_of_a_remote_machine
If this works on all machines, your eth0 network interface is set up.
After setting up your ppp and connecting to your Internet Service Provider (ISP), you will have another network interface (ppp0) and then will be able to telnet any machine in the world.
4.5.3 I have problems configuring my ppp dial out
GUI. If I were you, I would install kde and use kppp. kppp is really easy to configure and run. To set up your ppp dial out, run kppp (it is under the "K" menu "Internet, or you can run it from the xterm by typing kppp), press the "setup" button, create an account, and fill out the information required: telephone number, authentication protocol, and your Internet Service Provider's (ISP) domain name and the Domain Name Server (DNS) number of your ISP. All this information should have been provided to you by your ISP.
Next, I check if a device called /dev/modem exists and points to the right port. If necessary, I create it by symbolically linking it to the device /dev/ttyS1 (as root):
ls -l /dev/modem
ln -s /dev/ttyS1 /dev/modem
ttyS1 should work if your modem is on the port that DOS calls COM2. Use ttyS0 for COM1 and ttyS2 for COM3 and ttyS3 for COM4. The modem will not dial at all if a wrong port is chosen. For non-standard serial port setups, see the command setserial.
With old versions of kppp, you may get an error message complaining about a "lock". The solution then is to make sure that the file /etc/ppp/options is empty by editing it (as root):
pico /etc/ppp/options
and deleting the word "lock", then saving the file. This problem does not exist in the more recent versions of kppp.
RedHat 6.0 required one additional step: setting the "suid" ("substitute user id") so that "kppp" runs with the effective user id of root (because it needs to access hardware directly). Without it, kppp complains that "it was not properly set up" and "can't create lock file". This has to be done as root:
cd /usr/bin/
chmod a+s kppp
Troubleshooting. If your modem refuses to dial on the port that you are positive is chosen properly, maybe the modem is not set up properly (or maybe it is a "winmodem"? Then throw it away and buy a proper modem).
For example, in one instance, I had to run kppp setup, edit the "modem commands" and input ATZ1 as the "initialization string" (instead of the default ATZ for a standard Hayes-compatible modem). This particular modem would not dial unless it intialized with this atypical string "ATZ1".
If your telephone line requires pulse dialing (instead of the default touch-tone dialing), you may need to change the modem dialup command from "ATDT" (="ATtantion Dial Touchtone") to "ATDP" (="ATtantion Dial Pulse"). These commands work with any standard Hayes-compatible modem.

For some combinations of hardware on your computer, one may need to set up the modem on ttyS2 or ttyS3 (instead of the typical ttyS1, while ttyS0 is typically taken by mouse) because of interrupt conflict, e.g., with a network card. This can be achieved by setting the modem hardware (jumpers on your modem may need to be removed or repositioned, you have to look into the modem manual for specifics) and placing in the file /etc/rc.d/rc.local a line like this:

setserial /dev/ttyS3 irq 3

The standard PC settings for serial ports are:

port address of i/o port irq

/dev/ttyS1 0x03f8 4
/dev/ttyS1 0x02f8 3
/dev/ttyS2 0x03e8 4
/dev/ttyS3 0x02e8 3

I may use other, non-standard combinations or irq and i/o addresses to avoid conflicts with other hardware I might have. See man setserial for good a overview. Modem with uacceptable setup of irq and input-output address will not dial.

If your modem dials correctly and you are able to connect, but your authentication fails, perhaps your Internet Service Provider (ISP) uses a different authentication protocol. Call them and ask what authentication protocol they use. Or try "pap", "terminal-based" or "chap" (in your kppp setup) until you find the one which works with your ISP. "Terminal-based" always works for me if I only remember the password correctly.
In one instance, I had a problem with the reliability of establishing a connection (the error would pop up saying something like: "time-out for the pppd startup", and the connection would establish only once every few trials). The problem was solved by changing the "flow control" option (in the kppp "setup" under "device") from "CRTSCTS" to XON/XOFF. (Still CRTSCTS is the recommended flow control method in most cases.) In another case, opposite happened: communications was painfully slow because I did not set "flow control" to "hardware".
Random disconnects (after some time of correct connection) can have many causes. (1) They may be caused by "glitchy" drops of "data terminal ready" (DTR) signal or "carrier" signal. e.g., due to a noisy line. Most modems respond to that by hanging up. To change this default behaviour, you may need to add to your "modem initializati