1 .\" $OpenBSD: src/sbin/dhclient/dhclient-script.8,v 1.6 2011/04/04 11:43:20 krw Exp $
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33 .\" This software has been written for the Internet Software Consortium
34 .\" by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
35 .\" Enterprises. To learn more about the Internet Software Consortium,
36 .\" see ``http://www.isc.org/isc''. To learn more about Vixie
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44 .Nd DHCP client network configuration script
46 The DHCP client network configuration script is invoked from time to
50 .\" No standard client script exists for some operating systems, even though
51 .\" the actual client may work, so a pioneering user may well need to create
52 .\" a new script or modify an existing one.
53 In general, customizations specific to a particular computer should be done
55 .Pa /etc/dhclient.conf
60 needs to invoke the client configuration script, it sets up a number of
61 environment variables and runs
65 is set to the name of the reason why the script has been invoked.
66 The following reasons are currently defined:
67 BOUND, RENEW, REBIND, REBOOT, EXPIRE, FAIL and TIMEOUT.
68 .Bl -tag -width "ARPCHECK"
70 The DHCP client has done an initial binding to a new address.
71 The new IP address is passed in
73 and the interface name is passed in
75 Any options acquired from the server are passed using the option name
80 are replaced by underscores
82 in order to make valid shell variables, and the variable names start with new_.
83 So for example, the new subnet mask would be passed in
84 .Va $new_subnet_mask .
86 When a binding has been completed, a lot of network parameters are
87 likely to need to be set up.
90 needs to be created, using the values of
93 .Va $new_domain_name_servers
94 (which may list more than one server, separated by spaces).
95 A default route should be set using
97 and static routes may need to be set up using
98 .Va $new_static_routes .
102 effectively overwrites
103 .Pa /etc/resolv.conf ,
104 any information contained therein is lost.
105 If options must be passed to the resolver,
106 they may be contained in
107 .Pa /etc/resolv.conf.tail ,
108 which is appended to the generated
113 .\".Xr resolv.conf.tail 5
114 .\"for further information.
117 When a binding has been renewed, the script is called as in BOUND,
118 except that in addition to all the variables starting with $new_,
119 there is another set of variables starting with $old_.
120 Persistent settings that may have changed need to be deleted \- for example,
121 if a local route to the bound address is being configured, the old local
122 route should be deleted.
123 If the default route has changed, the old default route should be deleted.
124 If the static routes have changed, the old ones should be deleted.
125 Otherwise, processing can be done as with BOUND.
127 The DHCP client has rebound to a new DHCP server.
128 This can be handled as with RENEW, except that if the IP address has changed,
129 the ARP table should be cleared.
131 The DHCP client has successfully reacquired its old address after a reboot.
132 This can be processed as with BOUND.
134 The DHCP client has failed to renew its lease or acquire a new one,
135 and the lease has expired.
136 The IP address must be relinquished, and all related parameters should be
137 deleted, as in RENEW and REBIND.
139 The DHCP client has been unable to contact any DHCP servers, and any
140 leases that have been tested have not proved to be valid.
141 The parameters from the last lease tested should be deconfigured.
142 This can be handled in the same way as EXPIRE.
144 The DHCP client has been unable to contact any DHCP servers.
145 However, an old lease has been identified, and its parameters have
146 been passed in as with BOUND.
147 The client configuration script should test these parameters and,
148 if it has reason to believe they are valid, should exit with a value of zero.
149 If not, it should exit with a nonzero value.
152 The usual way to test a lease is to set up the network as with REBIND
153 (since this may be called to test more than one lease) and then ping
154 the first router defined in
156 If a response is received, the lease must be valid for the network to
157 which the interface is currently connected.
158 It would be more complete to try to ping all of the routers listed in
160 as well as those listed in
161 .Va $new_static_routes ,
162 but current scripts do not do this.
164 .\" Each operating system should generally have its own script file,
165 .\" although the script files for similar operating systems may be similar
166 .\" or even identical.
167 .\" The script files included in the Internet Software Consortium DHCP
168 .\" distribution appear in the distribution tree under client/scripts,
169 .\" and bear the names of the operating systems on which they are intended
172 .Xr dhclient.conf 5 ,
173 .Xr dhclient.leases 5 ,
174 .\".Xr resolv.conf.tail 5 ,
176 .Xr dhcpd 8 Pq Pa pkgsrc/net/isc-dhcpd4 ,
177 .Xr dhcrelay 8 Pq Pa pkgsrc/net/isc-dhcrelay4
180 The original version of
182 was written for the Internet Software Consortium by
183 .An Ted Lemon Aq mellon@fugue.com
184 in cooperation with Vixie Enterprises.
191 .An Kenneth R. Westerback Aq krw@openbsd.org .
193 If more than one interface is being used, there's no obvious way to
194 avoid clashes between server-supplied configuration parameters \- for
195 example, the stock dhclient-script rewrites
196 .Pa /etc/resolv.conf .
197 If more than one interface is being configured,
199 will be repeatedly initialized to the values provided by one server, and then
201 Assuming the information provided by both servers is valid, this shouldn't
202 cause any real problems, but it could be confusing.