Unix Support

Installing Red Hat Linux within the University of Cambridge

Contents

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Introduction

Here are some notes I have made based on installing Red Hat Linux version 6.0 on a Pentium system running a PCI bus motherboard. These notes are designed to supplement Red Hat's own installation instructions and not to replace them.

Unix Support maintains an NFS server with, among other stuff, a mirror of the Red Hat distribution. The server is called nfs-uxsup.csx.cam.ac.uk and the directory containing the mirror is /linux/redhat. This is NFS exported to the world. It is also available via anonymous FTP from the same machine. Login as user ftp or anonymous and give any old junk as your password (though it is tradition to give your e-mail address). The mirror can be found in /pub/linux/redhat.

These notes assume you have an ethernetted PC connected to the University network. If you don't then I'm afraid you're out of luck here. These notes also assume a small degree of computer literacy and intelligence on the part of the installer; they do not constitute a recipe that can be blindly followed.

Preinstallation checks

Hardware

There are certain bits of information about your hardware that you will need to know before you proceed with installing Linux. On a PCI based system, many of the cards can be autodetected. However, you will need to know certain facts. Unfortunately, because the retail world seems to grovel at the feet of Bill Gates it is often hard to find out exactly what sort of hardware you have. The shops will typically tell you "Don't worry; it's Windows-compatible." and ignore any technical questions. More worryingly, even if you precisely spec a machine for purchase some vendors have been known to deliver something different, saying that they've given you something better at no extra cost. So pore over the paper docs that came with your hardware, run the MS-DOS msd (MicroSoft Diagnostic) program from a floppy or your hard disc (if you have a copy of MS-DOS already installed), scour the startup screens when MS-DOS boots but get the following critical information:

Ethernet card
This is going to be a network installation; the operating system really does need to know what sort of ethernet card the machine has. Try to determine the manufacturer (the absolute minimum), the make, the version, and basically anything you can dig off it.
SCSI card
If you have a SCSI card, what sort is it? The card type is typically displayed during booting. If you do have a SCSI card then at least one SCSI peripheral should be attached to it and switched on before you do the installation. There are reports that the installation procedure cannot see the SCSI card unless it is being used for something.
Mouse
You need to know what sort of mouse you have. Mouse type is very hard to auto-probe for. Because of the Bill Gates Cult mentioned above, most serial mice (mice connected through a serial port (COM1:, COM2: etc.) come "Microsoft compatible" and if you haven't a clue then this is a good first guess. You will also need to know what serial port it is connected to (usually COM1:).
Graphics card
On a PCI bus system, this can usually be autodetected. It is still useful to know, if only so that you can check that the autodetect has a sensible result. If you don't have a PCI bus system then you will need to select the card from a list. Under these circumstances the data you need involve the chip set and the amount of video RAM (VRAM).
Monitor
This is the stage of the installation that comes with dire warnings. Pushing your monitor too hard can result in damage. Being too conservative can result in poor graphics. The Red Hat installation offers a list of monitor types to select from. If you are lucky yours is one of these. Look for the "real" make in the small text on the back of the monitor, not the rebadged, friendly writing on the front. If your monitor is not in the list then there are three pieces of information that you need about it:
Highest resolution
Monitors tend to support a subset of a common set of resolutions (640x480, 800x600, 1024x768 and 1280x1024). These specify how many pixels wide and deep the physical display will be.
Horizontal scan rate
This will be a figure in kHz (kilohertz) giving the number of horizontal scans that the monitor does per second. Common values vary from 25kHz to 125kHz.
Vertical scan rate
This will be a figure in Hz (hertz) giving the number of vertical sweeps of the screen the monitor does per second. This is often supplied as a range of values.
The monitor's documentation will present you with a choice of combinations of these values. Generally speaking, pick the highest resolution available without "interlacing". This will typically determine the horizontal and vertical scan rates. If it doesn't, pick from the remaining set the combination with the highest vertical scan rate. Interlacing, incidentally, is the process of taking two scans of the screen to fully draw it. The first scan draws half the pixels (every other row) and the second scan fills in the remaining half.

WARNING: Monitors can be very heavy and very, very unweildy. Even if your monitor is not on the large side, if you need to move it to get at the back it is still worth asking a friend to help. This can save bending over it and lifting at bad angles for your back.

Network configuration

As part of networking your system, whether as a Linux box or as an MS-DOS box, you will have been assigned an IP address and a name by ip-register@ucs.cam.ac.uk. You should have a copy of this letter, even if someone else (e.g. your CO) applied for the number. The letter asks that it be passed on to the person immediately responsible for the system. The letter has the following information:

IP Address
This is a series of four numbers between 1 and 254 separated by dots. It will be something like "131.111.8.2". This is the number that is unique to your computer and corresponds to your machine's name. NB: This is a fake IP address for the example. This is NOT your IP address.
Netmask
This is like an IP address but very likely the numbers will all be 0 or 255. It will usually have the value 255.255.255.0 though some (typically large) departments have the value 255.255.0.0. Other institutions will have still different numbers.
Default router
This is also called the "gateway". Common (but not universal) practice within the University is for the default router address to be the same as the machine's IP address except for the last of the four numbers being replaced by 62. So in the example above the default router might be 131.111.8.62.
Nameserver
The letter will also give you the IP addresses of your nearest nameservers. (These are the machines that store the lookup information that maps the name "bootes.cus.cam.ac.uk" into 131.111.8.1 for example. Some departments have their own, in which case you will be told about it if the Computing Service knows about it. Otherwise you will have been given the IP addresses of the two central nameservers that we run: 131.111.8.42 and 131.111.12.20. Pick one at random.

Booting

Go, either by NFS or FTP to the top of the Red Hat mirror. By NFS this is /linux/redhat and by FTP it is /pub/redhat. We will refer to this as the "top level directory". From there change directory to updates/6.0/images/i386. You need a copy of bootnet.img. You only need a copy of supp.img if you need support for PCMCIA cards. You only need a copy of rescue.img to do recovery work on trashed systems.

bootnet.img should be written directly to a floppy:

Linux
If you have a Linux system already then, if your floppy drive is accessed as /dev/fd0, you should give the following command to copy the file:
$ dd if=bootnet.img of=/dev/fd0 bs=1474560
MS-DOS, Windows
If you are using MS-DOS you have my deepest sympathies. You should get a copy of the rawrite program from the redhat-6.0/i386/dosutils subdirectory of the mirror's top level directory and use that to write the floppy.

As a precaution you should set the boot floppy to be read-only.

Now back up your system.

I repeat: BACK UP YOUR SYSTEM!

Installation

Navigation

The installation process from the user's point of view, consists of a series of screens containing queries for information. What you need to know about navigation and selection is described in this section.

Within a menu the arrow keys will move you up and down. The page up and down keys will move through the list much faster. If the menu is for selecting a single item from a list then simply leaving the desired item highlighted will suffice. If multiple items in the list are to be selected then they will come with checkboxes. An unselected check box looks like this: "[ ]" and a selected one, like this: "[*]". The SPACE bar toggles the selection of the item in the list.

The TAB key will move between items on a screen. For example, to move between OK, Cancel and Edit buttons press TAB to move from one to the next. A common combination is for there to be a menu followed by some buttons. The arrow and page keys move within the menu as described above, and the TAB key moves from the menu to the first button. TABbing is typically cyclic: hitting TAB when the focus is on the last item moves the focus back to the first item.

The RETURN key will hit the current button, i.e. the button moved to via the TAB key. (To "toggle" is to flip between two states; selected items become unselected and vice versa.) On a screen with a menu but no OK button it will also accept the current setting of the menu and move on to the next screen.

Booting from the floppy

Once you have backed up your system insert the boot floppy into the floppy drive that MS-DOS regards as A: and reboot. This will launch the installation program. It will first ask you for boot options. This is principally to launch a "rescue floppy" configuration. You will only need this if something has gone horribly wrong. For installations and upgrades, just hit return.

The system then loads Linux from the floppy and then presents you with a welcome screen with an OK button at the bottom. Hitting RETURN takes you on to the series of querying screens.

Basic configuration information

The language screen gives you the series of languages Red Hat supports. The default is English (actually American English, but let's not be too fussy) so you can just TAB to the OK button and hit RETURN.

The keyboard screen follows. You will probably have either a UK keyboard (one with the double quotes character as a shifted 2 and the pounds stirling character as a shifted 3) or a US keyboard (one with the commercial-at character as the shifted 2 and the hash or sharp character as the shifted 3). Get it right. One of the other differences is the location of the Unix pipe and the backslash characters. You do not want to work on a keyboard with these incorrectly mapped!

The next screen asks you to identify the installation method. Select "NFS image" (NFS is the "network file system"). This is the method that accesses our copy of the Red Hat distribution over the network.

Network configuration

Now that the installation program knows that the network is to be used, it ask you to identify the network card from a menu. Once you have selected the card, it will ask for options. The options are typically to autoprobe or to enter the options manually, with the default for that particular card as the upper menu item. Most modern cards support the autoprobe and have it as the upper, default menu item. If you select the manual entry you will need to give the i/o address and the IRQ number. If the card does not match the description or if the autoprobe fails, or if you type in the wrong manual entries the installation program will display an error screen saying that it could not locate the card and offer you a chance to try again.

If it can use the network card it will proceed to ask you for the boot protocol. The CUDN uses "static IP" for its IP numbering; your machine will always have the same number and need not apply for an address each time it boots.

The next screen asks your to configure TCP/IP and you will need the information from the letter from the University's IP Register issuing you with your IP address.

The first field asked for is the IP address.

When you TAB to the next entry, the netmask a default value will be created for you. If your IP address begins with 131.111 then you will get the default 255.255.0.0. This is only correct for certain (typically large) departments in the University. Use the netmask value given in the letter from IP Register.

The third field is the gateway machine address. This is the address of the route from your local network (department, college, whatever) to the rest of the world. A typically incorrect default will be created for you by the system and will need to be replaced. The letter from IP Register gives the address to use.

The fourth and final entry is for a primary nameserver. The nameserver is the system that maps between machine name and machine number (and vice versa.) Red Hat's default will almost certainly be wrong. If the IP Register knows of a nameserver on your network then the letter will inform you of it and you shyould use this local nameserver. Otherwise you will be pointed at one of the University's central nameservers, 131.111.12.20 and 131.111.8.42. If the nameserver works and is contactable then the installation script automatically works out your system's host name from the DNS. If it cannot get to the nameserver, or the nameserver does not recognise your IP address then you will be prompted for a hostname. This is a sign that something has gone wrong.

Selecting the NFS server

The next screen asks you to identify your NFS server. The machine name you should use is nfs-uxsup.csx.cam.ac.uk and the directory containing the installation image is /linux/redhat/redhat-6.0/i386.

After confirming the NFS server you should briefly see a message "in second stage install" which is the confirmation that you are no longer working from the boot floppy but from the NFS-mounted file system.

Selecting the system to install

If the installation program can see Linux partitions on your disc it will ask if you want to perform a fresh installation or an upgrade. For the purposes of this example we will select the Install option.

The next question asks what sort of installation you want to perform. It offers three alternatives: "Custom", "Server" and "Workstation". The "server" and "workstation" settings are simple default installations, whereas the "custom" install allows you to tinker. This document will start by describing the "workstation" installation. (A later revision of this document will describe the other two, I hope.)

The workstation installation option

There are up to two warning screens displayed, essentially notifying you that you are going to trash data. You have taken backups, haven't you?

You will then see a brief "scanning packages" message followed by a large number of "install status" windows, one for each package being installed.

Selecting the mouse

On a system with a mouse connected to the system bus, the installation program will automatically detect the presence of the mouse, but not its exact type. If you have a serial mouse the probing is less certain and may prompt you for whether or not you even have one.

In either case you will need to identify the type of the mouse and to specify whether or not you need three button emulation. If you have a two button mouse you do want it; if you have a three button mouse you don't.

Finally, in the case of serial mice, you will be asked which serial port it is connected to.

Confirming the network settings

After configuring the X settings (or abandoning X altogether) you will be prompted for the network configuration. You should select the choice to keep the current settings.

Setting the timezone

The next screen asks you to set the timezone. First you need to specify whether or not the hardware clock is set to GMT. If this is a Linux-only system then you are well advised to have your hardware clock on GMT. Leave the daylight saving to the operating system. Unfortunately, because Microsoft products are a heap of s**t, MS Windows requires the hardware clock to keep local time. If you have a dual boot system you need to work down to MS's standards here, I'm afraid.

After describing the machine clock, you need to set your timezone. The menu is long with a mixture of geographical regions and timezone names. Pick "GB". Don't forget about Page Up/Down on this menu.

Setting the root password

The penultimate screen asks you to set the root password. You know the drill: no real names, keep it secret, yadda yadda yadda...

Now think about this: when the system goes horribly wrong and you're not about who else knows the password? It is worth having a trusted deputy to also know the root password. Your local computer officer may also be a useful depository of such data (if and only if s/he has a secure place to keep them all).

Making a boot floppy

The next screen asks you if you want to make a custom bootdisk. You do.

The boot floppy is a copy of LILO configured for your particular system's set up which you can boot from should the copy on your disc get corrupted. You do want this floppy. Keep it safe too.

Configuring the X server

On PCI bus systems, the graphics card is automatically probed for. If it is found and recognised the installation program simply announces the card it has found.

On non-PCI bus systems, or if the card is unrecognised on a PCI bus system, you are presented with a menu of cards to pick from. Your card may be a variant of one of the cards in this list or be back-compatable with one. The "Unlisted card" option in this menu takes you to a menu wherein you specify the chip set on the card.

If you definitely need an X driver not in the list you will need to cancel the X installation and return to it later when you have the relevant driver.

If you do select a card from the list there will be another package download as the relevant package is loaded from the NFS server.

The next screen will ask you about your monitor, providing you with a list to select from. Recall the data you found from your monitor during the preinstallation checks. (How's your back, by the way?) If you can find your monitor in the list, select it. If you can't, you will need to go for the "Custom" entry and describe your monitor to the system.

Finally, the installation program will run a probe on your X server to see if the settings work at all. You will see your screen flash a few times. Things can go horribly wrong at this stage but typically problems will have been caught already. Theoretically, your monitor may blow up if you overclock it, but don't let me scare you.

If all goes well, you will be asked about screen resolutions. This screen will tell you the default it has selected (typically the highest resolution at 256 colours) and ask if you are happy with that or whether you want to choose. If you opt to choose you are presented with a screen with the various combinations possible. TAB will carry you beteen columns and arrows within the column. The SPACE bar toggles a selection on or off. You can have more than one option. If you do then once X is running, CTRL-ALT-PLUS will run you through the various settings.

Finally you will be asked if you want X running automatically at boot. You probably do.

Completion

Ta da! That's it; you've made it. Eject the floppy, hit RETURN and wait for your shiny new Linux system to boot.

Postinstallation activity

It's not quite all over yet, though the hardest part is now compete. Red Hat Linux installs, even as a workstation, with a few misfeatures which need to be corrected as soon as possible after installation.

/etc/inetd.conf

There are some entries that should be commented out of /etc/inetd.conf. You definitely want to comment out the pop-2, pop-3, imap, linuxconf and both time entries. The first three of these are responsible for most of the recent (successful) attacks against the University's computers. The linuxconf service also seems to be a frequent cause of security problems and needs to mature before being installed by default. You probably want to comment out gopher too unless you are really planning to run a gopher server. (Hint: don't.) Unless you plan to use the talk programs you should comment out the talk and ntalk entries too.

/etc/sysconfig/sendmail

Change the line that says "DAEMON=yes" to read "DAEMON=no".

This stops sendmail listening for incoming mail. You should not be receiving incoming email by SMTP unless you really know what you are doing.

Other services

Certain services are started at boot and shouldn't be. To turn them off use the chkconfig program as shown below. 

# chkconfig --level 12345 linuxconf off
# chkconfig --level 12345 lpd off
# chkconfig --level 12345 pcmcia off

Obviously, you should only turn off the pcmcia support if your system doesn't use it!

Note that you have to turn off linuxconf both in /etc/inetd.conf and as a boot option. It comes in two parts, and both need to be disabled.

Reboot?

To kick these changes into service you could now reboot.

If you want to be sophisticated, and learn for the future, you could do the following instead.

The inetd daemon rereads its /etc/inetd.conf configuration file when it receives the HUP signal. This is true for many daemons. We can find the process id of the inetd by looking in /var/run/inetd.pid. The /var/run/ directory is used for this purpose by most Linux daemons. We then use this to send the HUP signal (with the kill command) to the relevant proicess.

# more /var/run/inetd.pid
278
#  kill -HUP 278

The sendmail service has been reconfigured and up to three others have been told not to start at boot. None of these changes have taken effect yet. We will now shut down all four services and then restart just the sendmail service. The start/stop scripts all live in /etc/rc.d/init.d. 

# cd /etc/rc.d/init.d
# ./linuxconf stop
# ./lpd stop
# ./pcmcia stop
# ./sendmail stop
Shutting down sendmail: sendmail
# ./sendmail start
Starting sendmail: sendmail

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URL: http://www-uxsup.csx.cam.ac.uk/pub/doc/redhat/redhat6/notes-hedwig.html