TITLE: Creating a DHCP server from scratch
LFS VERSION: Any
AUTHOR: Thinus Pollard <12322741@puknet.puk.ac.za>
SYNOPSIS:
This hint handles the installation of the ISC DHCP daemon. The daemon is
used to automatically hand out ip addresses to client pc's on your
network. Obviously this is a much smarter way of doing things than to
physically go to each of the 150+ pc's on your network and setup the
network on all of them.
HINT:
1. Introduction
The idea behind dhcp is indeed very simple, yet it's an elegant solution to a
majorish problem. When a client PC on the network comes up, it sends a
DHCPDISCOVER packet. The dhcp server receives this packet, check the database
for the client's ip address, and sends a DHCPACK packet, informing the client of
an ip address it should use, or confirmation that the client should continue to
use the current ip. The ip address allocation can either be dynamic, or static
in which the dhcp server matches the client's MAC address to an ip address in
the database. This way you can ensure a certain network card always gets the
same ip on the network, and now you can start thinking about all kinds of
interesting routing tricks you can pull to make your network a good place to
be ;)
2. Packages to download
dhcp-3.0.tar.gz
ftp://ftp.isc.org/isc/dhcp/dhcp-latest.tar.gz
Web Page
http://www.isc.org
3. Installation
1. Unpack the dhcp package anywhere you like as long as it's in /usr/src.
2. The people at ISC sometimes have some funny ideas about the location of
certain files. We're gonna fix this.
1. Run the following in the top level directory to install to /usr
instead of /usr/local:
sed 's%usr/local%usr%' Makefile.conf > Makefile.conf.temp
2. You may just as well fix the manpaths in the file by:
sed 's%usr/man%usr/share/man%' Makefile.conf.temp > Makefile.conf
3. The server wants the database file in /var/state/dhcp. Not me, I
want it in /var/cache/dhcp, so...
sed 's%/var/state/dhcp%/var/cache/dhcp%' Makefile.conf \
> Makefile.conf.temp
4. The Makefile doesn't seem to know about linux-2.4, lets tell it ;)
sed 's/Linux 2.2/Linux 2.4/' Makefile.conf.temp > Makefile.conf
sed 's/linux-2.2/linux-2.4/' Makefile.conf > Makefile.conf.temp
5. It also has a high disregard for CFLAGS and CXXFLAGS
sed 's%\$(BINDEF) \$(CC_OPTIONS)%\$(BINDEF) \$(CC_OPTIONS) \
-O3 -march=i586%' Makefile.conf.temp > Makefile.conf
That should fix up the Makefile.conf
6. Edit the configure script and go to line no 82 change:
0) sysname=linux=linux-2.0 ;;
1) sysname=linux=linux-2.1 ;;
2) sysname=linux=linux-2.2 ;;
*) sysname=linux=linux-2.2 ;;
to
0) sysname=linux=linux-2.0 ;;
1) sysname=linux=linux-2.1 ;;
2) sysname=linux=linux-2.2 ;;
4) sysname=linux=linux-2.4 ;;
*) sysname=linux=linux-2.2 ;;
7. Change to the includes directory and run
sed 's%/etc/dhcpd.conf%/etc/dhcp/dhcpd.conf%' dhcpd.h > tmp~ &&
mv tmp~ dhcpd.h
sed 's%/etc/dhcpd.conf%/etc/dhcp/dhcpd.conf%' site.h > tmp~ &&
mv tmp~ site.h
8. Change to the includes/cf directory and run the following
sed 's%/var/state/dhcp%/var/cache/dhcp%' linux.h > linux.h.tmp
mv linux.h.tmp linux.h
3. Now do a
./configure &&
make &&
make install
4. Configuration
1. Do a 'touch /var/cache/dhcp/dhcpd.leases'
2. Here is my config file. Read the man-pages and the DHCP mini howto for
more information. The config file goes into /etc/dhcp/dhcpd.conf
# Begin /etc/dhcp/dhcpd.conf
authorative; # For the subnets it's configured for
ddns-update-style none; # Lotsa trouble here... rtfm
deny bootp; # we're not using it, so why allow it?
one-lease-per-client true; # Should make sense
subnet 192.168.1.0 netmask 255.255.255.0 { # You need to change the ip
# if you're using something
# else
option broadcast-address 192.168.1.255; # Self explanitory
option routers 192.168.1.1; # Available routers
option domain-name-servers 192.168.1.1; # Available DNS
option domain-name "rivendell.org.za"; # Domain name
option ip-forwarding false; # You don't really want clients doing
# NAT ;)
option netbios-name-servers 192.168.1.1; # SMB Nameservers on your
# network
pool {
range 192.168.1.240 192.168.1.254; # Range of available ip's
default-lease-time 300;
max-lease-time 300;
allow unknown clients;
}
pool {
range 192.168.1.11 192.168.1.239;
default-lease-time 86400;
max-lease-time 604800;
deny unknown clients;
}
}
use-host-decl-names true;
# For static addresses, use these host declariations.
host legolas {
hardware ethernet 00:80:AD:87:7F:59;
fixed-address 192.168.1.10;
}
# For dynamic addresses, use these host declariations. Without the
# "fixed address" part the host is still known, it's just allowed to
# get any ip from the pool
host gimli {
hardware ethernet 00:80:AD:87:7F:59;
}
# End /etc/dhcp/dhcpd.conf
3. And the init script...
#!/bin/sh
# Begin $rc_base/init.d/dhcpd
# Based on sysklogd script from LFS-3.1 and earlier.
# Rewritten by Gerard Beekmans - gerard@linuxfromscratch.org
source /etc/sysconfig/rc
source $rc_functions
case "$1" in
start)
echo -n "Starting DHCP daemon..."
loadproc /usr/sbin/dhcpd -q
;;
stop)
echo -n "Stopping DHCP daemon..."
killproc dhcpd
;;
restart)
$0 stop
sleep 5
$0 start
;;
status)
statusproc /usr/sbin/dhcpd
;;
*)
echo "Usage: $0 {start|stop|restart|status}"
exit 1
;;
esac
# End $rc_base/init.d/dhcpd
4. Add a symlink in rc[345].d to start the dhcpd server just after starting
the network and a symlink in rc[0126].d to stop the server just before
stopping the network
5. The End
1. You should be done now, give it a whirl. Now go read the man-pages and
start servin them ip's ;)
2. Any comments, flames, suggestions etc is always welcome. Have a nice
day ;)