How to setup Linux as DHCP client

How to setup Linux as DHCP client

_________________________________________________________________

_Disclaimer:_ The information contained herein is NOT official
information of any kind and there are no warranties to the accuracy of
the data. All information is provided in good faith. Use at your own
risk.

_________________________________________________________________

Vladimir Vuksan, [email protected]
v 2.1, Last revised: October 11th, 1997

Introduction

This HOWTO explains how to setup your Linux system to work in a DHCP
environment as a client (DHCPcd). If you are looking for a DHCP server
you need to read DHCPd mini-HOWTO at
http://sunsite.unc.edu/LDP/HOWTO/mini/DHCPd. DHCP is a protocol that
allows a client machine to obtain network information from a server.
Many organizations are starting to use it because it eases network
administration especially in large networks or networks which have
lots of mobile users. DHCP is also being heavily used by cable
Internet service provider such as MediaOne Express, Time Warner etc.
More info about DHCP can be found in DHCP FAQ.

Road Runner Service

If you have Road Runner cable service check out
http://people.qualcomm.com/karn/rr/index.html. If that doesn't solve
your problem try following.

2.1.x kernels

If you are running a > 2.1.30 kernel (don't remember the exact number
and www.linuxhq.com is down currently) you might encounter a problem
with the dhcpc. According to Dan Khabaza:
_"The changes are due to differences in ipv4 network package, in the
way it sets the defaults for several fields."_

Dan has provided a patch for it that can be obtained at
http://www.cro.net/~vuksan/dhcppatch. To apply it just copy it to the
dhcpcd source directory (instruction how to get source are in the
following section) and type

patch

dhcpcd should compile cleanly after the patch has been applied.

Method

_Step 1)_ No matter what distribution you are using you will need
to download the DHCP client daemon for Linux. The package you need to download
is called dhcpcd and the current version is 0.65. The description
of the package reads:

Title: dhcpcd
Version: 0.65
Entered-date: 05MAY97
Description: dhcpcd is an RFC2131 compliant DHCP client daemon. It
gets an IP address and other information from a
corresponding DHCP server, configures the network
interface automatically, and tries to renew the lease
time according to RFC2131. It works in the RFC1541
compliant mode when the '-r' option is specified.
So far it is found that dhcpcd 0.65 works fine with the
following DHCP servers:
1. ISC's dhcpd-BETA-5.15
2. DHCP server on Windows NT server 3.51
3. DHCP server version 1.3b by WIDE project.
4. DHCP server in the SolarNet PC-Admin 1.5 package
5. DHCP server used in the Time Warner Cable's
Internet Access Service
See the "Changes" file if you want to know the difference
from the previous version.
Keywords: DHCP, client, Linux
Author: [email protected] (Yoichi Hariguchi)
Maintained-by: [email protected] (Yoichi Hariguchi)
Primary-site: ftp.kobe-u.ac.jp:/pub/PC-UNIX/Linux/network/dhcp
33kB dhcpcd-0.65.tar.gz
Alternate-site: sunsite.unc.edu:/pub/Linux/system/network/daemons
33kB dhcpcd-0.65.tar.gz
Original-site:
Platforms: Linux 1.2.xx, 1.3.xx, 2.0.x
Copying-policy: GPL

_Note:_ Support for Bell Atlantic ADSL modems has been announced for
version 0.7.

Slackware

You can download the latest copy of the DHCPcd from any sunsite mirror
or following:

ftp://ftp.cdrom.com/pub/linux/sunsite/system/network/daemons/.

ftp://sunsite.unc.edu/pub/Linux/system/network/daemons

ftp://ftp.kobe-u.ac.jp/pub/PC-UNIX/Linux/network/dhcp
(Primary site in Japan)

Download the latest version of dhcpcd.tar.gz

Unpack it

tar -zxvf dhcpcd-0.65.tar.gz

cd into the directory

cd dhcpcd-0.65

make

You need to be root to do the following

make install

This will create the directory /etc/dhcpc where DHCPcd will store the
DHCP information and dhcpcd file will be copied into /usr/sbin.
Now skip to Step 2

RedHat

DHCPcd is included in the standard RedHat distribution as an RPM and
you can find it on your distribution's CD-ROM in RPMS directory or you can
download it from:

ftp://tsx-11.mit.edu/pub/linux/distributions/redhat/redhat-4.2/i386/RedHat/RPMS
/dhcpcd-0.6-2.i386.rpm.

and install it with

rpm -i dhcpcd-0.6-2.i386.rpm

Alternatively you can compile your own version by following the steps
outlined in the Slackware part. When done go to Step 2

Debian

There is deb package of DHCPcd at

ftp://ftp.debian.org/debian/stable/binary/net/

or you can follow the Slackware installation instructions.

In order to unpack the deb package type

dpkg -i /where/ever/your/debian/packages/are/dhcpd*deb

When done go to Step 2

__________________________________________________________________________

_Step 2)_

Following step(s) are depended on your needs.

_a) _ If you need network connectivity only occasionally you can
start dhcpcd from the command line (you need to be root to execute it)
by typing

/usr/sbin/dhcpcd

When you need to down (turn off) the network type

/usr/sbin/dhcpcd -k

You now only lack nameservers configuration file (/etc/resolv.conf).
For instructions on how to create a resolv.conf go to
Step 3

_b) _ If you want (need) network connectivity all the time and would
like dhcpcd to start at boot time follow the steps below.

Slackware

In order to make the system initialize using DHCP during boot type:

cd /etc/rc.d
mv rc.inet1 rc.inet1.OLD

This will move the old network initialization script into rc.inet1.OLD.
You now need to create the new rc.inet1. It should look as follows:

#!/bin/sh
#
# rc.inet1 This shell script boots up the base INET system.
#
# Version: @(#)/etc/rc.d/rc.inet1 1.01 05/27/93
#

HOSTNAME=`cat /etc/HOSTNAME` #This is probably not necessary but I
#will leave it in anyways

# Attach the loopback device.
/sbin/ifconfig lo 127.0.0.1
/sbin/route add -net 127.0.0.0 netmask 255.0.0.0 lo

# IF YOU HAVE AN ETHERNET CONNECTION, use these lines below to configure the
# eth0 interface. If you're only using loopback or SLIP, don't include the
# rest of the lines in this file.

/usr/sbin/dhcpcd

Save the above file as rc.inet1. Reboot your computer. Go to Step
3.

RedHat

This information was provided to me by nothing ([email protected])

Removed my static ip and name from /etc/resolv.conf. However, I
did leave in the search line and my two nameserver lines (for some reason my
dhcpcd never creates a /etc/dhcpc/resolv.conf, so I have to use a static
/etc/resolv.conf).

In /etc/sysconfig/network I removed the HOSTNAME and GATEWAY
entries.
I left the other entries as is (NETWORKING, DOMAINNAME, GATEWAYDEV).

In /etc/sysconfig/network-scripts/ifcfg-eth0 I removed the IPADDR,
NETMASK, NETWORK, and BROADCAST entries. I left DEVICE and ONBOOT as is.
I changed the BOOTPROTO line to BOOTPROTO=dhcp.

Save the file. Reboot your computer and go to Step 3

Debian

It appears that there isn't a need for any DHCPcd configuration because:

From: Heiko Schlittermann

The dhcpcd package installs it's startup script as usual for debian
packages in /etc/init.d/, here as /etc/init.d/dhcpcd,
and links this to the various /etc/rc?.d/ directories.

The contents of the /etc/rc?.d/ dirs is then executed at boot time.

If you don't reboot after installing you should consider starting
the daemon manually:

/etc/init.d/dhcpcd start

Go to Step 3.

__________________________________________________________________________

_Step 3)_ This step should be the same for all
distributions.

After your machine reboots your network interface should be configured.
Type:

ifconfig

You should get something like this

lo Link encap:Local Loopback
inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0
UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1
RX packets:302 errors:0 dropped:0 overruns:0 frame:0
TX packets:302 errors:0 dropped:0 overruns:0 carrier:0 coll:0

eth0 Link encap:Ethernet HWaddr 00:20:AF:EE:05:45
inet addr:24.128.53.102 Bcast:24.128.53.255 Mask:255.255.254.0
^^^^^^^^^^^^^^^^^^^^^^^
UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU:1500 Metric:1
RX packets:24783 errors:1 dropped:1 overruns:0 frame:1
TX packets:11598 errors:0 dropped:0 overruns:0 carrier:0 coll:96
Interrupt:10 Base address:0x300

If you have some normal number under inet. addr you are set. DHCPcd is a
daemon and will stay running as long as you have your machine on. Every three
hours it will contact the DHCP server and try to renew the IP address lease. It
will log all the messages to the syslog (on Slackware /var/adm/syslog) if you
need to check up on it.

One final thing. You need to specify your nameservers. There are two ways to do
it, you can either ask your provider to provide you with the addresses of your
name server and then put those in the /etc/resolv.conf or DHCPcd will obtain
the list from the DHCP server and will build a resolv.conf in /etc/dhcpc.
I decided to use DHCPcds resolv.conf by doing the following:

Back up your old /etc/resolv.conf

mv /etc/resolv.conf /etc/resolv.conf.OLD

If directory /etc/dhcpc doesn't exist create it

mkdir /etc/dhcpc

Make a link from /etc/dhcpc/resolv.conf to /etc/resolv.conf

ln -s /etc/dhcpc/resolv.conf /etc/resolv.conf

If that doesn't work try this (fix suggested by [email protected])

This last step I had to perform only because my dhcpcd doesn't
create an /etc/dhcpc/resolv.conf. In /etc/sysconfig/network-scripts/ifup I
made the following changes (which are a very poor hack, but they work
for me):

#################################

elif [ "$BOOTPROTO" = dhcp -a "$ISALIAS" = no ]; then
echo -n "Using DHCP for ${DEVICE}... "
/sbin/dhcpcd -c /etc/sysconfig/network-scripts/ifdhcpc-done ${DEVICE}
echo "echo \$$ > /var/run/dhcp-wait-${DEVICE}.pid; exec sleep 30" | sh

if [ -f /var/run/dhcp-wait-${DEVICE}.pid ]; then
echo "failed."
exit 1
else
rm -f /var/run/dhcp-wait-${DEVICE}.pid
echo "done."
IPSETUP=yes
fi
fi

#################################

I changed to:

elif [ "$BOOTPROTO" = dhcp -a "$ISALIAS" = no ]; then
echo -n "Using DHCP for ${DEVICE}... "
/sbin/dhcpcd
echo "echo \$$ > /var/run/dhcp-wait-${DEVICE}.pid; exec sleep 30" | sh

# if [ -f /var/run/dhcp-wait-${DEVICE}.pid ]; then
# echo "failed."
# exit 1
# else
# rm -f /var/run/dhcp-wait-${DEVICE}.pid
# echo "done."
IPSETUP=yes
# fi
fi

#################################

Now sit back and enjoy :-).

Troubleshooting

If you have followed the steps outlined above and you are unable to access
the network there are several possible explanations:

_I. Your network card is not configured properly_. During the boot up
process your Linux will probe your network card and should say something along
these lines:

eth0: 3c509 at 0x300 tag 1, 10baseT port, address 00 20 af ee 11 11, IRQ 10.
3c509.c:1.07 6/15/95 [email protected]

If a message like this doesn't appear your ethernet card might not be recognize
d
by your Linux system. If you have a generic ethernet card (a NE2000 clone) you
should have gotten a disk with DOS utilities that you can use to set up the
card. Try playing with IRQs until Linux recognizes your card (IRQ 9,10,12 are
usually good).

_II. Your DHCP server supports RFC 1541_

Try running dhcpcd by typing

dhcpcd -r

Use ifconfig to check if your network interface is configured (wait few seconds
for the configuration process, initally it will say Inet.addr=0.0.0.0)

__________________________________________________________________________

Thanks to all the people that contributed with their ideas and
suggestions:

Heiko Schlittermann ([email protected])

Jonathan Smith ([email protected])

Dan Khabaza ([email protected])

Hal Sadofsky ([email protected])