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Post Installation

 

Preparation

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Introduction

After installation, there are a number of things that need to be done to make a system reasonably useable. There are lots of issues that could be included here, but this is a minimal set. Some of these are related to deeper issues that will be covered later.

Configuring the Startup Interface

There is nothing wrong with the graphical startup as long as things go well with your X configuration. If not, you may not be able to boot. Since you are going to be changing your system's configuration regularly I recommend that you change the default boot behavior to the text screen.

xdm

xdm is the X Display Manager, and represents a different operational mode for the operating system. If you choose to run xdm, it becomes the login manager for the init process. When you boot the machine, xdm runs and presents a nice graphical logon screen. If you logoff, xdm presents the login screen again. If you have X terminals or other X devices logging in to your computer, they will also see the xdm interface.

Virtual Consoles

Linux supports the concept of virtual consoles - up to 63, and the default is to define 6 of these. If you boot up and log in, you will be a virtual console 1. You can change to one of the other consoles by entering ALT-F(unction)-N, which changes you to console N. F(unction)-N is one of the function keys (F1 to F6) at the top of the keyboard. You can also use CTRL-ALT-F(n), or use ALT-LEFT(RIGHT)-ARROW to cycle through the available consoles.

In the newer versions of XFree86, these consoles also work under X, so you can have a one or more non-X sessions running. However, you cannot have more than one X server running at one time. Also, if you change to a text console and back to X, you might find that your graphics card has problems with this and doesn't get the display quite right.

Information

The man pages are critical in solving many linux system administration problems and you need to make sure they are available. Try typing man ls (or any other command) to insure that the man pages are working.

  • whatis database so that the man -k and apropos commands will work.

    Another useful tool is locate (or locate). To create the locate database enter locate -u.

    Network Configuration

    First, you need to test your network configuration to see if it works properly.

    Network Configuration with system-config-network

    If you didn't get your networking properly configured during install, or if networking comes along later, you can configure it manually (which will be discussed later in the course) or you can use system-config-network (RCN) or neat. A warning is in order. While RCN can make certain system administration tasks easier, you can also create some major problems that are hard to find and fix. So use it carefully. If you ever get confused about what you've done, abort the session and restart.

    Run /sbin/system-config-network or /sbin/neat; you should see the graphical interface for the network configurator.

    There are five tabs on the interface which allow you to configure five things; the logical device, the interface card, the host information, the IPSec policies and the Domain Name System.

    Logical Device

    This is the most critical part. You should see a logical device named eth0 and its status should be active. If there is no logical device you will need to add one using the add button, but that probably indicates a major installation problem.

    If you click on the eth0 device and then Edit, you will see the following:

    Check the Statically set IP addresses option and fill in your IP address, subnet mask and default gateway address. Also, make sure that the Activate device when computer starts box is checked.

    Then you can close this box. You can also enter routing information, and in the case of multiple network cards, the device here, but you don't need to do this now.

    Hardware

    It is unlikely that you will want to try to configure the hardware, but this is a place where you can provide special options that the driver can use.

    Hosts

    The hosts tab allows you to enter hosts that should be in your /etc/hosts file. This file provides a fast way to lookup addresses without doing a DNS lookup. It is essential that the 127.0.0.1 and your system's IP address be included in the list. If they aren't, add them. You can also add other addresses, such as printers or commonly used system names, but you don't have to do this.

    DNS

    This tab allows you to enter a hostname and names of DNS servers. Also, you can enter search paths. These are DNS suffixes to try if you type in an unqualified name, such as telnet scalliwag. Typically you enter your domain (cs.montana.edu), but you can enter other domains that you commonly access.

    IPSec

    IPSec is an encrypted messaging system that can be used to set up private tunnels. We won't do anything with this immediately.

    Troubleshooting

    If you have problems, first execute an ifconfig command and and you will see something like this:

    If there is no eth0, you have no interface. If you have one, but the RX and TX show no packets and/or errors, the device is there and recognized, but not currently working. Using RCN, make sure that the device is activated. If you have used RCN to modify your configuration, try rebooting and then look in /var/log/boot.log for the term eth0. If it shows up as succeeded, it should be working but if not, you have hardware or driver problems.

    If everything checks out, try pinging a host with the DNS name. If that doesn't work, try it with the IP address. If that works then you have a problem with DNS. Make sure that your DNS servers addresses are properly set up.

    If anything you try to do gets a Host unreachable message, then the problem is with your default gateway. Make sure the configuration is correct with RCN. For some reason, you may need to reboot if you change the default gateway in order to have it recognized.

    Configure Root

    The root account needs to be carefully configured. You should run BASH as the shell, although that is a somewhat personal choice. You need to set up a path for the root user and whatever aliases and other characteristics you want in the ~root/.bashrc file.

    Boot Loader Configuration

    Every system needs a boot loader that is initially stored in memory and which then reads the operating system from disk and executes the initialization procedures. There are two possible choices for Red Hat 8.0 - LILO and GRUB.

    GRUB

    GRUB (GRand Unified Boot loader) is a generic type of boot loader that can handle many different operating systems and multiple boot systems seamlessly. To configure GRUB, you modify the file /etc/grub.conf which is simply a link to /boot/grub/grub.conf. You will notice that the file /boot/grub.conf/menu.lst also points to grub.conf. That's because the normal configuration file for GRUB is menu.lst but the Fedora folks like this other naming scheme. Under most circumstances, you won't have to modify this file at all since the install process asks questions that provide the necessary information. But you might change your mind about something.

    A couple of notes:

    An example grub.conf file is:

    The records starting with title describe operating systems that can be booted by grub. In this case, there is one operating system which is:

    To actually configure GRUB, you can manually edit this file, or you can run grub, which has more than 40 different commands. For the time being, you might be interested in adding a password to your GRUB boot. You can do this with:

    This assumes that you want your password to be encrypted, which you do.

    There are of course many other things that you can do and some will be discussed later.

    LILO

    LILO stands for Linux Loader, and it is the program that can boot Linux and other operating system. There is quite a bit to LILO, but the simple version is this:

  • LILO is a boot manager or boot loader. There are lots of these around but LILO is the standard for Linux.
  • LILO operation is controlled by /etc/lilo.conf.
  • If you change lilo.conf or your kernal configuration, you have to execute the LILO command in order for the changes to be known by the boot loader.
  • The permissions on lilo.conf should be 700 or 600.
  • An example lilo.conf file is:

    Each of these statements tells LILO something about your boot-up configuration. We will discuss LILO more later and the man pages for lilo and lilo.conf are quite complete.

    One option that is handy is the password option:

    If present, it tells LILO not to allow a boot request until the password is entered. This will not stop someone with a floppy disk from booting the system if it is properly configured.

    Rescue Disk

    The boot disk that you make is designed to boot the system that you have installed. It will not boot your system unless you have the Linux kernel and file system on a hard drive. This isn't much help if your installation is corrupted by bad fortune or active stupidity (it happens). What you need for that is a bootable Linux floppy or CD, which is a self-contained Linux system not an install set. You can boot up to a running Linux system without any other support, and then you can access your hardware to make changes. In times past, an image for the rescue disk was included in the images directory of your installation CD, but not in later versions of Red Hat. For more information check out this page.

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