[ 9 May 1998
The Linux DHCPcd mini-HOWTO is no longer being maintained. The DHCPd and
DHCPcd have been merged into a single mini-HOWTO called DHCP. Please
feel free to contact me at <linux-howto@sunsite.unc.edu> if you have any
questions or concerns. ]
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, vuksan@veus.hr
$Revision: 1.5 $ $Date: 1998/04/21 12:21:11 $
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 stands for Dynamic
Host Configuration Protocol. It 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 on 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 < dhcppatch
dhcpcd should compile cleanly after the patch has been applied. Note
that this patch works only against dhcpcd 0.65 :-(.
Another patch has been provided by Paul Rossington if you have
problems with the one above. It is actually the whole if.C file. Get
it at http://www.cro.net/~vuksan/if.C and copy it to the dhcpcd source
directory.
Other alternative when running 2.1.x kernels is to use dhcpcd 1.3.3
which is a modified version that has been written by Sergei Viznyuk
sergei@phystech.com in order to avoid problems with 2.1.x kernels. You
can fetch it at:
http://www.cps.msu.edu/~dunham/out/dhcpcd-1.3.3.tar.gz
RedHat 5.0 users
DHCPcd configuration under RedHat 5.0 is really easy. All you need to
do is start the Control Panel by typing
control-panel
Then select "Network Configuration" and under eth0 interface define
DHCP as your protocol. Other parameters should be left blank.
Token Ring network
If you are trying to run dhcpcd on the Token Ring Network it will not
work. This is the solution provided to me by Henrik Stoerner:
The problem is that dhcpcd only knows about Ethernet cards. If it
finds a Token-Ring card, it refuses to do anything with it and reports
"interface is not ethernet".
The solution is to apply a simple patch to the dhcpcd-0.65 sources. I
have put up a small web page with the patch, RedHat RPM-files and a
precompiled binary at http://eolicom.olicom.dk/~storner/dhcp/
The patch has been sent to the dhcpcd maintainer, so hopefully it will
be included in a future release of dhcpcd.
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 0.70. The
description of the package reads:
Title: dhcpcd
Version: 0.70
Entered-date: 05NOV97
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 0.70 works with the
following DHCP servers:
1. ISC's dhcpcd-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 Time Warner Cable's
Internet Access Service
6. DHCP server used in Bell Atlantic ADSL
See the "Changes" file if you want to know the difference
from the previous version.
Keywords: DHCP, client, Linux
Author: yoichi@fore.com (Yoichi Hariguchi)
Maintained-by: yoichi@fore.com (Yoichi Hariguchi)
Primary-site: ftp.kobe-u.ac.jp /pub/PC-UNIX/Linux/network/dhcp
33kB dhcpcd-0.70.tar.gz
Alternate-site: sunsite.unc.edu /pub/Linux/system/Network/daemons
33kB dhcpcd-0.70.tar.gz
Original-site:
Platforms: Linux 1.2.xx, 1.3.xx, 2.0.x
Copying-policy: GPL
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-0.70.tar.gz
cd into the directory
cd dhcpcd-0.70
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 (nothing@cc.gatech.edu)
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 nothing@cc.gatech.edu
with a little amendment by Henrik Stoerner)
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
#################################
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
#################################
Notice the ! (bang) in
if [ ! -f /var/run/dhcp-wait-${DEVICE}.pid ];
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 becker@cesdis.gsfc.nasa.gov
If a message like this doesn't appear your ethernet card might not be
recognized by your Linux system. If you have a generic ethernet card
(a NE2000 clone) you should have received 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)
If this solves your problem add the "-r" flag to the boot up scripts
from Step 2) ie. instead of
/sbin/dhcpcd
you will have
/sbin/dhcpcd -r
III. During bootup I get error message "Using DHCP for eth0 ...
failed" but my system works fine.
You are most likely using RedHat and you haven't followed instructions
acurately :-). You are missing the ! (bang) in one of the if
statements Jump back up and read it again.
IV. My network works for few minutes and then stops responding
There are some reports of gated (gateway daemon) screwing up routing
on Linux boxes which results in problem described above. Check if
gated is running
ps -auxww | grep gate
If it is try removing it with RedHat's RPM manager or removing the
entry in /etc/rc.d/
V. My ethernet card is recognized during boot up but I still get "NO
DHCPOFFER" message in my logs. I also happen to have a PCMCIA ethernet
card.
You need to make sure that you have the 10BaseT port ("phone" plug) on
your network card activated. Best way to verify it is to check what
kind of connector your card is configured for during bootup e.g.
eth0: 3c509 at 0x300 tag 1, 10baseT port, address 00 20 af ee 11 11, IRQ 10.
^^^^^^^^^^^^
3c509.c:1.07 6/15/95 becker@cesdis.gsfc.nasa.gov
I have received reports of laptop users having this kind of problems
due to the PCMCIA utilities (specifically ifport) which would set the
connector type to 10Base2 (thinnet). You have to make sure you use
10BaseT for your connection. If you are not reconfigure the card and
restart the computer.
VI. I have followed all the steps but still my machine is not able to
connect
The cable modem will usually memorize the ethernet address of your
network card so if you connect a new computer or switch network cards
you will somehow have to "teach" your cable modem to recognize the new
computer/card. Usually you can turn of the modem and bring it back up
while computer is on or you will have to call tech support and tell
them that you have changed a network card in the computer.
You have firewall rules (ipfwadm rules) that disallow port 67/68
traffic used by DHCP to distribute configuration info. Check your
firewall rules carefully.
_________________________________________________________________
Thanks to all the people that contributed with their ideas and
suggestions. Especially the following:
Heiko Schlittermann (heiko@os.inf.tu-dresden.de)
Jonathan Smith (jps2@ra.msstate.edu)
Dan Khabaza (danyh@iil.intel.com)
Hal Sadofsky (sadofsky@math.uoregon.edu)
Henrik Stoerner (henrik_stoernet@olicom.dk)
Paul Rossington (paulrossington@unn.unisys.com)