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Root over NFS - Another Approach
George Gousios, cs98011@icsd.aegean.gr
v1.0, 2001-09-12
This HOWTO does not intend to replace the existing Root over NFS
Howto's. It is just another approach, particularly useful in large
system installations. It is the result of many days of trying to
setup a system for the University of the Aegean computer labs. The
installation method described here is up and running. The HOWTO is
dedicated to all of those guys who programmed these exceptionally good
OS and tools. Also dedicated to all people that encouraged me to
write it.
______________________________________________________________________
Table of Contents
1. Introduction
1.1 The setting
1.2 The alternatives
1.3 General Principles
2. Setting up the server
2.1 Setting up the NFS server
2.2 Setting up the DHCP/BOOTP server
2.3 Preparing the base system
3. Setting up the clients
3.1 Errata
3.2 Fiddling with scripts and files!
3.2.1 How to setup a swap partition
3.2.2 Modifying
3.2.3 Copying password files
3.3 Booting the base system
3.4 Configuring the system
3.4.1 Configuring the language
3.4.2 The X window system
3.4.3 Configuring network access for KDE2
4. Preparing the boot disk
4.1 Building a kernel
4.2 Creating the boot disk
4.3 The kernel command line
5. The magic time
6. Other Stuff
6.1 Contributors
6.2 Copyrights
6.3 Contacting the author
6.4 Changelog
7. Appendix
7.1 Appendix A - A script for creating host directories
7.2 Appendix B - A script to create the dhcpd.conf file using
7.2.1 The arp.dat2dhcpd.conf script
7.3 Appendix C - A sample XF86Config file
______________________________________________________________________
1. Introduction
This document does not resemble a common HOWTO, meaning referencing to
general principles, but it is rather an on-hand approach to a by
nature complex matter. It borrows the structure of the current Root
over NFS , but differs from it in the following points:
<20> It provides a working solution fom the distribution used. The
distribution specific points should be applicable to all major
distributions (RedHat,SuSE,Debian).
<20> It uses more up to date tools, ex NFS v3.0, kernel 2.4.0, dhcp
instead of bootparamd.
<20> All steps are described in detail, letting the reader to adapt them
to his own system. No scripts!
This HOWTO expects that you have a general knowledge of what you are
up to, so first read the Diskless Nodes HOW-TO.
1.1. The setting
It is a common case a University computer lab to have a lot PC's
running Windows 98 or/and NT and a powerful UNIX server to satisfy the
need of an alternative operating environment. This UNIX server is
most of times idle or meerly accessed by telnet and running stupid
tasks. On the other hand, students, especially those attending a
computer science department, feel like taking full advantage of it,
just for fun or for "educational purposes" (breaking in, hacking
it...). The restrictive environment of telnet does not allow us to
enjoy the use of a power server.There are 2 alternatives to that:
<20> Try to persuade the department' s headmaster to approve of the
purchase of a bunch of new Unix workstations.
<20> Try to persuade the same guy to approve of transforming the server
to a diskless node server.
The network at the computer lab consists of the following.
<20> UNIX server: SUN Enterprise 3500 with 2 64 bit SPARC@366 Mhz
processors and 512 MB of memory. A real monster, isn't it?
<20> "Dumb" target workstations: 60-70 PC's with variable
configurations, ranging from PII 266 to PIII 450 with 64-128 MB
RAM.
The task I had to accomplish was the following: Provide a complete
working solution without new expenses and without modifying anything
but the necessary on the server.
1.2. The alternatives
Being the responsible for the project, I had to choose between a
variety of solutions about it. I choose the following, for the
reasons illustrated:
<20> The new 2.4 kernel: It provides a robust and fast solution, using
less memory than the old 2.2 series. If it is important for your
users to attach devices to their PC's then it is the only solution.
Also provides NFS v3, and more efficient memory management.
<20> The KDE 2.1.1 desktop environment: VERY stable, easy to use,
Internet enabled, makes the transition from Windows to Linux
desktop almost effortless. GNOME + Afterstep is another option, but
not as mature as a solution as KDE.
<20> SuSE 7.0 distribution: My favorite one, IMHO the most balanced
between ease of use and understanding of a Linux system structure.
1.3. General Principles
To be able to boot a Linux system, you have to provide it with the
following:
<20> The /sbin directory. There exists the init programm, which is
responsible for starting other programms and start up scripts
during the boot process. Also, the /sbin directory contains the
startup scripts in the case of SuSE, some useful programms like the
portmap programm and many other programms that are needed before
you mount the /usr directory.
<20> The /lib directory. It contains the libc libraries that are
absolutely necessary if your init is dynamically linked.
<20> The /bin directory. It contains file commands and shells for
running startup scripts.
<20> The /etc directory. It contains configuration files for most
programms and the rc.d directories that is the default for startup
scripts.
<20> The /var directory. It is a spool area for programms that want to
write somewhere. It is divided into many subdirectories with
alternate usability.
<20> The /dev directory. It contains character and block special devices
that allow programms to communicate with the computers devices via
the kernel.
You should notice that after a clean install, the total size of
these directories is not that big, ranging from 30 to 40 MB. The
main load of files exists in the /usr and /opt directories. So, it
is possible to create a directory for every diskless client
containing the above listed directories and mount points for
directories like /usr that will be exported by the server. The
boot process, as assumed by this document, is the following:
1. The user reboots the computer, and using a diskette boots the Linux
kernel.
2. The kernel takes control of the system, identifies the system
devices, and uses BOOTP to obtain the IP address matching the NIC
's hardware address.
3. The init programm is started. Before switching to a run level, it
calls a script described in the /etc/inittab file. This script is
responsible for building the library cache, initialise and mount a
swap file, load some system specific kernel modules and set the
hostname.
4. The boot script finishes and the init programm switches to the
specified runlevel. It starts to execute the scripts located into
the /etc/rc.d/rcX directory where 'X' is the name of the runlevel.
These scripts are responsible for starting the portmapper and
mounting the NFS exported /usr, /home and /opt directories.
5. The user is able to login.
To sum up, the system administrator has to do the following tasks:
<20> Prepare a clean install of the system to be exported to the
diskless hosts.
<20> Create the host specific directories
<20> Control what is going to be started during the diskless clients'
boot proces
<20> Prepare the server to export some directories and start a bootp
service.
2. Setting up the server
The first, and less tricky, thing to do is to setup the server. The
server must be prepared to run these services:
<20> NFS, preferably version 3, for exporting the following directories:
/usr, /lib/modules, /opt (at least at SuSE) and /home (unless you
have a dedicated file server).
<20> DHCP server (in bootp mode), for matching the clients' MAC
addresses to IP addresses.
Also, the administrator has to create directories for each client,
containing nessesary startup files and programs. The directory
scheme created for the installation described was like this one:
______________________________________________________________________
/usr/local/linux-
|-/base-
| |-/bin
| |-/sbin
| |-/etc
|
|-/workstations-
| |
| |-195.251.160.100
| | |-/bin
| | |-/sbin
| | |-/etc
| |
| |-195.251.160.101
| |-195.251.160.102
| |-base(symbolic link to ../base)
______________________________________________________________________
The /base directory contains the whole file system you want to export
to your clients. The per IP directories contain files that are needed
before mounting the /usr or /lib/modules directories, like the /etc
folder. This is a confortable directory structure for 2 purposes: i)
You can easily create a basic system at the base directory and copy
the per workstation files at the workstation directories easily, with
an entry level bash script ii) You can easily add or delete or update
workstations by modifying the directories under /workstations. A
script for copying the appropriate files (which will be discused
later) can be found in Appendix A.
2.1. Setting up the NFS server
An NFS server can be set up in two ways:
<20> Using the /etc/exports file at BSD-compliant Unices like Linux of
FreeBSD.
<20> Using the /etc/dfs/dfstab at SysV Unices like Solaris.
/etc/exports: The /etc/exports file controls the directories to be
exported and the export options per workstation. It has a
structure like the following (Linux):
______________________________________________________________________
/path/to/dir1 ws1(options) ws2(options)....
/path/to/dir2 ws3(options) ws1(options)....
______________________________________________________________________
Options include ro or rw, root_squash, wsize, tcp, version.
Have a look at the nfs or the exports man page and the NFS Howto for a
more detailed description of what these options mean.
/etc/dfs/dfstab:A typical dfstab file on Solaris should look like the
following:
______________________________________________________________________
share -F nfs -o rw=193.250.160@,ro=193.250.161@ /export/home
share -F nfs -o ro=193.250.160@,root=193.250.161.132 /export/engineering
______________________________________________________________________
Of course, these options are discused in detail at the dfstab man
page.
The directories we want to export are /usr/local/linux/base/usr,
/usr/local/linux/base/opt, /usr/local/linux/base/lib/modules and
/home, assuming that you 've followed the suggested structure.
Optimising NFS
Of course, this is none of our business but here are some general
principles:
<20> Reduce the TCP window size (parameter wsize for Linux) to whatever
is closest to the MTU of your network type. For Ethernet, a good
value of wsize is 2048 bytes as long as the MTU is 1536 bytes.
This is generally a good idea because the main traffic load between
the clients and the server consists of little packets and only in
the case of starting large programms like X or StarOffice there is
a big number of fragmented packets. Of course this may vary in your
case, according to the needs of your users.
<20> If you plan to have a large installation, break the space for your
workstations into 2 or more SCSI disks. This will allow consequent
writes and reads on both disks, increasing responce and reducing
latency before a request completes
<20> Always use NFS v3 over TCP. The main reason for migrating from v2
to v3 is the writeback case it offers on both the workstation and
the server. Also, mounting NFS over TCP lets you use the first
recomentation. \end{itemize} For further optimising use a packet
analyzer like Ethereal or tcpdump and dicide your needs.By the way,
Sun has written an excellent guide to optimizing NFS performance
which, although emphasised on Solaris, is applicable to every
modern Unix and is accessible online at http://docs.sun.com
<http://docs.sun.com>.
2.2. Setting up the DHCP/BOOTP server
Although there are many DHCP or BOOTP servers 'out there', some of
which are proprietary, the best option is to use the reference IETF
DHCP server. It is the least vulnerable and the most extensible DHCP
available. The main server configuration is done through the
/etc/dhcpd.conf file. This file is divided into two sections, the
general server configuration and the host specific configuration. A
typical dhcpd.conf file looks like this, in case that the DHCP/BOOTP
server is used in BOOTP mode:
subnet 193.250.160.0 netmask 255.255.255.0 {
range 193.250.160.10 193.250.160.12;
}
host george{
hardware ethernet 00:60:08:2C:22:20;
fixed-address 193.250.160.10;
}
host earth{
hardware ethernet 00:A0:24:A5:FD:E0;
fixed-address 193.250.160.12;
}
This structure is fairly easy to be understood by everyone. For every
diskless client we have to supply the programm with a 'host'
declaration providing a pair of hardware and IP adresses. The host
name provided in the 'host' statement can be everything, but there is
a conversion to use the real host name of the client having the
specific IP. The range statement in the subnet declaration is not
necessary to be the range that you want your clients to have. In fact,
if these clients are normal workstations with an operating system that
during its boot uses DHCP to obtain an IP address it is not
recommended to have the same IP for their operation as diskless
clients. If you have specific needs, have a look at dhcpd.conf man
page.
Another difficulty is how to obtain the IP - MAC address pairs for a
large network. The solution is a nice little programm called arpwatch.
This programm runs at the background and keeps track of the IP - MAC
address pairs of the computers that your computer has contacted in a
file that you have specified. The only thing you have to do is to ping
the computers you want. At Appendix B there is a script that starts
arpwatch, pings a range of subsequent IP's and creates the dhcpd.conf
file. If you want to do it manually, start arpwatch when your network
is at its peak of usage and wait for some time. On a shared medium
network (Ethernet, Tokenring) arpwatch will track down all different
IP 's and hardware addresses.
2.3. Preparing the base system
To prepare the base system just install your favorite distribution to
a mountable partition on a hard disk with a Unix like operating system
already installed. Install all the programms you want to be available
to your users. Then you have to transfer the whole partition
preserving the links and the character or block devices. This is best
done using the tar programm. Boot the previously installed system and
execute the following command, assuming that you have mounted the new
partition at /mnt:
tar cpvf system.tar /mnt/.
This command will create a tar archive at the current directory with
the whole system to be served to the diskless clients. Then just copy
the tar archive to the server using a CDROM or through the network and
extract it at the base directory. The command to do this is:
tar xvf system.tar /usr/local/linux/base
3. Setting up the clients
3.1. Errata
In order to setup the clients, we have to work on the base system.
First, we will make some modifications to the startup scripts by hand
and second we will boot a workstation with the base system to make
sure it works and to polish some details. Note that this part is very
distribution specific and perhaps some of those described here are not
applicable to your case. I can only guarantee that this works for
SuSE 7.0. Please, feel free to send me distribution specific copies of
this page!
3.2. Fiddling with scripts and files!
After init is started, it executes a script described in /etc/inittab.
This script has a very spesific job to do: Bring the system in a state
that other programms can be started. In most distributions I can think
of this script does the following:
1. Mounts the /proc, /dev/pts and swap filesystems.
2. Activates raid arrays and fscks the root filesystem.
3. Adjusts the clock.
4. Starts the kernel deamon for autoloading of modules.
5. Executes user defined client scripts.
6. Set some kernel parameters.
On most distributions I have checked this script is very well
commented and it is possible for an experienced user to remove some
lines that are not wanted or not applicable during a network boot.
I 've also noticed that all programms started do not require the
/usr directory to be mounted. If you are trying to netboot a host
you must do the following modifications to this script:
<20> Remove all entries that do fsck or initialise raid arrays, and add
to the top of the script this command : mount -o remount,rw /
because the client has to have rw access to the root directory when
it boots.
<20> Do not let the kernel deamon start until all partitions are mounted
<20> Mount a swap partition. This is described later.
<20> Start the portmapper. If your system has a specific directory for
starting bootup scripts, place the portmapper startup script there
giving it the highest priority possible, for example: ln -s
/etc/rc.d/portmap /etc/rc.d/boot/S01portmap if you are using SuSE.
<20> Place the NFS filesystem mounting script in the system specific
directory for boot scripts with priority lower than the portmapper,
for example ln -s /etc/rc.d/nfs /etc/rc.d/boot/S02nfs for SuSE.
<20> Remove all entries that automount local partitions, and all entries
that start an automounter deamon for RedHat.
3.2.1. How to setup a swap partition
This is tricky business! Swapping over NFS is not allowed by the
kernel and not functioning either. You cannot use swapon on files that
are on an NFS mounted filesystem. We have to do some tricks to enable
it:
1. Create the swap file. Its size can be variable but for a machine
with 128 MB of RAM a swap size of 40-50 MB seems reasonable. The
command to create the swap file is: dd if=/dev/zero of=/var/swap
bs=1k count=Xk where X stands for the number of MB your swap should
be. It is also a necessity to put the swap file under /var as long
as it is mounted at boot.
2. Format the swap file using the mkswapfs command.
3. Initialise a loopback device using the swap file. The command is
losetup /dev/loop0 /var/swap.
4. Mount the loopback device with the command mount /dev/loop0 swap.
You have to initialise a swap partition at the very beginning of
the boot process. So place commands 2-4 somewhere near to the top
of the startup script. The first command is very time
consuming,especially in the case of a loaded network so just copy a
swap file in the base system and do not delete it when you create
directories for each host.
3.2.2. Modifying /etc/fstab
The /etc/fstabfile contains entries for automounting file systems at
boot. In our case, we have to place the following lines at the end of
it:
server_IP:/usr/local/linux/base/usr /usr nfs nfsvers=3,wsize=2048,tcp 0 0
server_IP:/usr/local/linux/base/opt /opt nfs nfsvers=3,wsize=2048,tcp 0 0
server_IP:/usr/local/linux/base/lib/modules /lib/modules nfs nfsvers=3 wsize=2048,tcp 0 0
fileserver_IP:/home /home nfs nfsvers=3,wsize=2048,tcp 0 0
Also, do not forget to comment out lines that mount local partitions.
Save this file as /etc/fstab.new because it should not be activated
yet, as long as we have to boot the base system first.
3.2.3. Copying password files
You must provide the system with to files to let the users perform a
login. To do this just copy the files /etc/passwd and /etc/shadow from
your file server to the base system. Notice that you have to do it
every time you add a user to the system, or a user changes his/her
password, so can best be done by creating a cron job.
3.3. Booting the base system
To boot the base system we have to create a boot disk first. Go to
the next section and create a boot disk as recommended. Please, change
the 'append' line to this one:
append init=/sbin/init root=/dev/nfs
ip=X:Y:195.251.160.254:255.255.255.0:::'off'
nfsroot=Y:/usr/local/linux/base vga=0x318
(Of course, in a sigle line)
where X stands for an unused IP address in your network and Y for the
IP address of the NFS server. Of course, you have to export the
/usr/local/linux/base directory from the NFS server with the
rw,no_root_squash options. Now boot the base system. Everything
should work OK, but I don' t think that there is a possibility that
you succeeded from the first boot! There are many obscure points,
that you have forgotten to edit or I have forgotten to mention.
This is the standard method to boot the base system and to add
programms or a new kernel to your installation. So backup the files
you have edited as well as the boot disk image.
After succeeding to boot the system, you are in a complete linux
enviroment. Login as root and enjoy a first ride in your newly
created system! Now comes the hard time... You have to disable some
services that startup automatically and remove some programms not
needed by the users.
3.4. Configuring the system
Nearly all distributions start these services:
<20> inetd, the Internet superdeamon responsible for starting other
deamons like telnet, ftp etc.
<20> syslogd, the logging deamon. Not needed on a diskless client not
needed because all the modifications are done to files easyly
replacable.
<20> httpd, the apache webserver. Not needed for obvious reasons.
<20> dhcpclient. Needed for automatic aquisition of an IP address. At
out case, this is done by the kernel.
<20> lpd, the line printer deamon. This is needed only when you have a
printer connected to a host. In most cases, this is not needed.
Also, according to your installation, there may be started sshd,
nscd, cupsd and other network services not needed on clients. To
disable these services, remove their entries from the runtime
directory under /etc/rc.d/X. There is a more elegant way to do
this under SuSE or RedHat, using Yast or Linuxconfig. For Yast, go
to System administration ---> Change configuration file and using
search locate the entries for every service you want to stop.
Then, uninstall all these services from the base system. The only
service that seems reasonable to me to be left running is the
NameServer caching deamon, which is able to reduce network traffic a
lot.
Now, you have to edit some files:
<20> /etc/resolv.conf Used to provide a nameserver. Add these entries:
nameserver xxx.xxx.xxx.xxx and domain xxxxx , replacing x with the
correct values.
<20> /etc/hosts Used to match IP addresses to host names localy. Provide
the basic servers' names of your network.
<20> /etc/nntpserver Used to provide a news server. Just append the
nameserver 's hostname.
<20> /etc/fstab Restore the fstab.new file we have created earlier.
3.4.1. Configuring the language
Perhaps, you do not leave in the US or the UK, like me, so you have to
configure the language. This is simply done through the .profile
file. Just add the following: export LANG="X"where X is your natural
language. Then, download a console font which supports your codepage
and set, with the help of Yast, the keyboard keymap. Copy .profile to
/etc/skel of the file server or to all the users' home directories.
3.4.2. The X window system
If you want to provide a working X enviroment for clients with
different graphics hardware, you have to use the XFBDev server. If you
followed the instructions on howto create a boot disk, you would now
be in framebufer mode at 1024x768@16M colors, which is sufficient for
use with X windows. Now, you have to configure the X server to load
the framebuffer driver. SuSE provides an exellent tool for configuring
X wherher it might be version 3 or 4. It is called sax for X 3.3.x and
sax2 for X 4.x. To use XFBDev driver start sax with the -s XF86_FBDev
option and configure the server according to your hardware. In case
you do not use SuSE, most of the work must be done by hand. Create a
basic /etc/X11/XF86Config file using xf86config4. Please choose
entries that are as much as possible closer to your needs. Then edit
the /etc/X11/XF86Config. This file is devided into sections that
start with the keyword 'Section' and end with 'EndSection'. Do the
following modifications:
<20> Section "Files": Add the path to the direcory where you 've put
your fonts.
<20> Section "Module": Load the GLX module if you want REALLY SLOW Open
GL graphics (Load glx)!
<20> Section "InputDevice, Driver="mouse"": Add the following lines if
you want to use a wheel mouse:
Option "Buttons" "5"
Option "ZAxisMapping" "4 5"
<20> Section "Device": Replace everything with the following:
BoardName "AutoDetected"
Driver "fb"
Identifier "Device[0]"
VendorName "AutoDetected
<20> Section "Modes": Replace everything with the following:
Identifier "Modes[0]"
Modeline "1024x768" 71.39 1024 1040 1216 1 400 768 768 776 802
<20> Section "Screen": Replace everything with the following
DefaultDepth 16
SubSection "Display"
Depth 16
Modes "1024x768"
EndSubSection
Device "Device[0]"
Identifier "Screen[0]"
Monitor "Monitor[0]"
<20> Section "ServerLayout": Replace everything with the following:
Identifier "Layout[all]"
InputDevice "Keyboard[0]" "CoreKeyboard"
InputDevice "Mouse[1]" "CorePointer"
Screen "Screen[0]"
and then replace the first argument of the InputDevice directives with
the identifiers which can be found earlier in the file.
I thing that it should be a working configuration for framebuffer sys<79>
tems. For further reference take a look at the XF86Config and the
xf86cfg4 man pages. You will find a working XF86Config file at
Appendix C.
3.4.3. Configuring network access for KDE2
KDE is the most extensible, configurable and internet enabled window
manager available, even if we count some commercial ones that are
proud of it! To download KDE, ftp to ftp.kde.org and get the rpms for
your distribution. There, you can also find vanilla sources and other
related projects.
The main configuration to KDE is done through the K Control Center.
There you can find options for configuring the fonts, colors,
backgrounds etc. The most important thing you can configure is the
LAN browsing deamon that KDE incorporates, lisa. There is also a
readme file under \$KDE2ROOT/share/apps/lisa. After you configure
lisa, you have to make it (or her?) start in the background every time
the computer is started. Find the lisa 's configuration file under
/root. Copy it under /etc. Aftewards, place the command lisa -c
/etc/lisa.conf at the /etc/rc.d/boot.local file, or the similar for
your installation. Now tell me, which is easiest to search a network
Windows or Linux?
If your users are coming from the Windows world, they are familiar to
find programms at the damned 'Start' menu. To make their transition
easy, edit the KDE menu with the Menu Editor programm and add or
remove applications there. Then, copy the .kde2 directory from you
directory to the /etc/skel directory of your file server. Every new
account you create will have access to the menu (and the settings) you
have created.
4. Preparing the boot disk
To prepare a boot disk we just want a kernel, syslinux and a 1,44MB
diskette. Syslinux is tiny boot loader, designed specifically to boot
a kernel and pass some arguments through its command line using a
diskette. As we will see it very easy to configure, too.
4.1. Building a kernel
Always choose the newest kernel to build. As of this time of writing
(Wed Sep 12 17:28:22 2001) the newest kernel is 2.4.9. Building an
older kernel can only save you time updating the nesessary programms.
Also, be sure you have the program versions described in
/usr/src/linux/Documentation/Changes. It is a good idea to compile
the kernel using the base system to be served. The kernel can be build
according to your needs of drivers, but it must contain the following
options:
<20> Build in support for the cient 's network card (Network device
support ---> Select your card driver).
<20> Build in support for the BOOTP protocol (Networking options --->
IP: kernel level autoconfiguration ---> IP: BOOTP support).
<20> Build in support for NFS and root over NFS (File systems --->
Network File Systems ---> NFS file system support and File systems
---> Network File Systems ---> NFS file system support ---> Root
over NFS).
<20> Build in support for loopback devices (Block devices ---> Loopback
device support).
Do not forget to compile in the VESA framebuffer driver. Then go on
with the familiar kernel compilation routine. Unless you have
build the kernel using the base system, copy all the modules
created to the base/lib/modules directory of the exported directory
structure. The new kernel resides at
/usr/src/linux/arch/i386/boot.
You also have to set the root device to your kernel. You have to use
the rdev programm. Execute the following commands:
mknod /dev/boot255 c 0 255
rdev /path/to/kernel/file /dev/boot255
4.2. Creating the boot disk
Now, we have to use the syslinux programm. Insert a disk into the
first floppy drive and run:
syslinux -s /dev/fd0
Mount the floppy and notice that syslinux has written 2 files:
syslinux.cfg and ldlinux.sys. The second is the boot loader
executable. The syslinux.cfg is the programm configuration file. A
typical structure for that file is the following:
default linux
append init=/sbin/init root=/dev/nfs
ip=:195.251.160.10:195.251.160.254:255.255.255.0:::'bootp'
nfsroot=195.251.160.10:/usr/local/linux/ws/\%s vga=0x318
prompt 1
timeout 30
readinfo 2
The default statment is the kernel name to be booted and the append is
the command line to be passed to the kernel. Now, you have to copy the
kernel you have created to the floppy and rename it to 'linux'.
4.3. The kernel command line
To boot a diskless client, its kernel must have the following command
line options:
<20> init=/sbin/init: If your init programm is elsewhere just change the
path.
<20> root=/dev/nfs: An alias to say the kernel that it has to mount its
root directory over nfs
<20> ip: This command line option tells the kernel how to get it's IP
address and which is the NFS server's address
<20> nfsroot: Tells the kernel to mount this directory as its root. The
% is an alias to the host 's IP address.
<20> vga: If you want to be able to start X windows in framebuffer mode,
switch to a framebuffer mode. The one given stands for 1024x768@16M
colors.
All these options are discussed in detail in
/usr/src/linux/Documentation/nfsroot.txt. Read it and adjust the
given command line to your needs.
Now you have created the boot disk you are ready to test the system
you have build. Start the NFS and BOOTP services and boot a client
with the boot disk. No one has been able to do it from the first time.
So go on to the next section!
5. The magic time
In this section will be discused all the problems that you have and
the changes that you propose to the installation. Please feel free to
email me and ask about any difficult or not mentioned points in this
document. My email is cs98011@icsd.aegean.gr
Q: A DHCP is already running. How do I configure BOOTP, so as no
interaction is made with the DHCP?
A: This was the main problem I faced when I installed the system on a
running network. DHCP and BOOTP use the same port. When a windows
client boots, it issues a DHCP/BOOTP request to locate its IP (of
course in case of dynamic IP). When the DHCP server responds, it also
returns the IP's of DNS servers, print servers and Domain Controlers.
My BOOTP server was responding faster than the Microsoft DHCP server,
an so Windows clients were unable to locate their Domain controler.
This resulted to users not being able to login! The solution described
here was donated by D. Spinellis.
Open the /usr/src/linux/net/ipv4 file. This is were all BOOTP
autoconfiguration is done. Search for udph.source,udph.dest
variables. You will see that they are set to the standard 67/68
request/responce ports. Change BOTH values so they use an unused UDP
port in your network. A good port pair that no application uses it is
967/968. Now, start your DHCPd with the -p 967 option. Everything must
be working OK!
6. Other Stuff
6.1. Contributors
<20> Diomidis Spinellis: Structure and typographical corrections, the
DHCP/BOOTP conflict resolution.
6.2. Copyrights
This document is GNU copylefted by Georgios Gousios
<mailto:cs98011@icsd.aegean.gr>.
It is covered by the GNU documentation licence.
Permission to use, copy, distribute this document for any purpose is
hereby granted, provided that the author's / editor's name and this
notice appear in all copies and/or supporting documents; and that an
unmodified version of this document is made freely available. This
document is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY, either expressed or implied. While every effort
has been taken to ensure the accuracy of the information documented
herein, the author / editor / maintainer assumes NO RESPONSIBILITY for
any errors, or for any damages, direct or consequential, as a result
of the use of the information documented herein
6.3. Contacting the author
The author may be contacted via e-mail. For any change, question,
error that must be corrected please feel free to contact me. For every
contribution you make for this document, your name will be mentioned
in the contributors section.
6.4. Changelog
<20> v0.8, Thu May 24 17:37:13 2001 : First draft written.
<20> v1.0, Fri May 25 01:36:25 2001 : The first version is complete (in
HTML).
<20> v1.05, Thu Jul 19 19:09:58 2001: Structure and typos corrections.
Also, tranfered to LaTeX.
<20> v1.1, Wed Sep 12 18:23:29 2001: Transfered to LinuxDoc SGML,
donated to the LDP.
7. Appendix
7.1. Appendix A - A script for creating host directories
#!/usr/bin/bash
#This is a script for creating host directories using the
#directory scheme illustrated before in this document.
#It is written on Solaris and I did not test it on Linux.
#Execute it at the ws directory.
#Needs as input a file containing space separeted IP
#addresses named addr, for example bash# ./script addr
#This file must be like this: 195.251.160.10 195.251.160.11 195.251.160.13 ....
echo "Creating the tar archive"; echo
cd base
tar cpf linux.tar ./bin ./dev ./etc ./lib ./sbin ./var
mv linux.tar /usr/local/linux/ws/linux.tar
cd ..
echo "Creating host directories"; echo
for addr in $(cat addr)
do
echo "Working on host $addr"
mkdir $addr
cd $addr
echo " ---Creating nessesary directores"
mkdir boot
mkdir cdrom
mkdir floppy
mkdir home
mkdir mnt
mkdir opt
mkdir proc
mkdir root
mkdir tmp
mkdir usr
echo " ---Extracting tar archive"
ln -s ../linux.tar ./linux.tar
tar xf linux.tar
rm linux.tar
echo " ---Removing unnessesary files"
rm -R ./lib/modules/*
rm -R ./var/yp
rm -R ./var/X11R6/sax
rm -R ./var/tmp
rm -R ./var/state/dhcp
rm -R ./var/squid
rm -R ./var/run/*
rm -R ./var/opt
rm -R ./var/named
rm -R ./var/mysql
rm -R ./var/lib/amanda
rm -R ./var/lib/codadmin
rm -R ./var/lib/firewall
rm -R ./var/lib/apsfilter
rm -R ./var/lib/gdm
rm -R ./var/lib/misc
rm -R ./var/lib/nobody
rm -R ./var/lib/pcmcia
rm -R ./var/lib/pgsql
rm -R ./var/lib/rpm/*
rm -R ./var/lib/setup
rm -R ./var/lib/wvdial
rm -R ./var/lib/wwwrun
rm -R ./var/lib/xdm
rm -R ./var/lib/xkb
rm -R ./var/lib/YaST/*
rm -R ./var/lib/zope
rm -R ./var/log/*
rm -R ./var/cache/*
rm -R ./var/games
rm -R ./var/adm/*
echo " ---Deciding the hostname"
nslookup $addr |sed -n "s/^Name: *//p" >etc/HOSTNAME
cd ..
i=$(($i+1))
echo
done
echo "Removing the tar archive"
rm linux.tar
echo
exit 0
7.2. Appendix B - A script to create the dhcpd.conf file using arp<72>
watch
#!/bin/bash
#A script that starts arpwatch, pings a range of addresses and creates an
#/etc/dhcpd.conf file from the output of arpwatch.
#The arp.dat2dhcpd.conf programm is described later.
#Do not forget to edit the i variable and the while statement to specify
#the range of the addresses you want to ping
i=128;
echo "Starting arpwatch";echo
arpwatch
while [ "$i" -lt 253 ]
do
addr=195.251.160.$i
echo "Now pinging $addr"
ping -c 5 $addr >/dev/null
i=$(($i+1))
done
echo
exit
killproc arpwatch
echo "Creating /etc/dhcpd.conf"
cat /var/lib/arpwatch/arp.dat |arp.dat2dhcpd.conf >/etc/dhcpd.conf
7.2.1. The arp.dat2dhcpd.conf script
#!/usr/bin/perl -n
($ether, $ip,$stup1,$name) = split;
if ($name eq "") {
print "
host host$i {
hardware ethernet $ether;
fixed-address $ip;
}
";
$i++;}
else{
print "
host $name {
hardware ethernet $ether;
fixed-address $ip;
}
"}
7.3. Appendix C - A sample XF86Config file
#This file should let X 4.0.1 work in 1024x768@16M colors
#with the fbdev driver using the linux's framebuffer
Section "Files"
RgbPath "/usr/X11R6/lib/X11/rgb"
FontPath "/usr/X11R6/lib/X11/fonts/75dpi:unscaled"
FontPath "/usr/X11R6/lib/X11/fonts/local"
FontPath "/usr/X11R6/lib/X11/fonts/misc:unscaled"
FontPath "/usr/X11R6/lib/X11/fonts/100dpi:unscaled"
FontPath "/usr/X11R6/lib/X11/fonts/Type1"
FontPath "/usr/X11R6/lib/X11/fonts/URW"
FontPath "/usr/X11R6/lib/X11/fonts/Speedo"
FontPath "/usr/X11R6/lib/X11/fonts/misc"
FontPath "/usr/X11R6/lib/X11/fonts/75dpi"
FontPath "/usr/X11R6/lib/X11/fonts/100dpi"
FontPath "/usr/X11R6/lib/X11/fonts/PEX"
FontPath "/usr/X11R6/lib/X11/fonts/cyrillic"
FontPath "/usr/X11R6/lib/X11/fonts/latin2/misc"
FontPath "/usr/X11R6/lib/X11/fonts/latin2/75dpi"
FontPath "/usr/X11R6/lib/X11/fonts/latin2/100dpi"
FontPath "/usr/X11R6/lib/X11/fonts/latin7/75dpi"
FontPath "/usr/X11R6/lib/X11/fonts/kwintv"
FontPath "/usr/X11R6/lib/X11/fonts/truetype"
FontPath "/usr/X11R6/lib/X11/fonts/uni"
FontPath "/usr/X11R6/lib/X11/fonts/ucs/misc"
FontPath "/usr/X11R6/lib/X11/fonts/ucs/75dpi"
FontPath "/usr/X11R6/lib/X11/fonts/ucs/100dpi"
FontPath "/usr/X11R6/lib/X11/fonts/xtest"
EndSection
Section "ServerFlags"
AllowMouseOpenFail
EndSection
Section "Module"
EndSection
# This section is no longer supported
# See a template below
# Section "XInput"
# EndSection
Section "Keyboard"
Protocol "Standard"
XkbRules "xfree86"
XkbModel "microsoft"
XkbLayout "us"
EndSection
Section "Pointer"
Protocol "PS/2"
Device "/dev/psaux"
SampleRate 60
BaudRate 1200
Buttons 5
EndSection
Section "Monitor"
Identifier "Primary-Monitor"
VendorName "Unknown"
ModelName "Unknown"
HorizSync 29-64
VertRefresh 47-90
Modeline "1400x1050" 59.93 1400 1416 1704 1816 1050 1050 1055 1097
Modeline "1280x960" 59.90 1280 1296 1552 1664 960 960 965 1003
Modeline "1600x1000" 59.90 1600 1616 1968 2080 1000 1000 1004 1044
Modeline "1024x864" 59.89 1024 1040 1216 1328 864 864 870 902
Modeline "800x600" 58.55 800 816 928 1040 600 600 608 626
Modeline "1152x864" 59.99 1152 1168 1384 1496 864 864 870 902
Modeline "1280x1024" 59.90 1280 1296 1552 1664 1024 1024 1029 1070
Modeline "640x480" 37.44 640 656 720 832 480 480 486 501
Modeline "1024x768" 59.89 1024 1040 1216 1328 768 768 774 802
Modeline "1600x1200" 59.90 1600 1616 1968 2080 1200 1200 1204 1253
EndSection
Section "Device"
Identifier "Primary-Card"
VendorName "---AUTO DETECTED---"
BoardName "---AUTO DETECTED---"
EndSection
Section "Screen"
Driver "fbdev"
Device "Primary-Card"
Monitor "Primary-Monitor"
DefaultColorDepth 16
SubSection "Display"
Depth 32
Modes "default"
EndSubSection
SubSection "Display"
Depth 24
Modes "default"
EndSubSection
SubSection "Display"
Depth 16
Modes "default"
Virtual 1024 768
EndSubSection
SubSection "Display"
Depth 8
Modes "default"
EndSubSection
EndSection
Section "Screen"
Driver "fbdev"
Device "Primary-Card"
Monitor "Primary-Monitor"
DefaultColorDepth 16
SubSection "Display"
Depth 32
Modes "default"
EndSubSection
SubSection "Display"
Depth 24
Modes "default"
EndSubSection
SubSection "Display"
Depth 16
Modes "default"
Virtual 1024 768
EndSubSection
SubSection "Display"
Depth 8
Modes "default"
EndSubSection
EndSection
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