[ 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 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)