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DHCLIENT-SCRIPT(8) DragonFly System Manager's Manual DHCLIENT-SCRIPT(8)
dhclient-script -- DHCP client network configuration script
The DHCP client network configuration script is invoked from time to time
In general, customizations specific to a particular computer should be
done in the /etc/dhclient.conf file.
When dhclient(8) needs to invoke the client configuration script, it sets
up a number of environment variables and runs dhclient-script. In all
cases, $reason is set to the name of the reason why the script has been
invoked. The following reasons are currently defined: BOUND, RENEW,
REBIND, REBOOT, EXPIRE, FAIL and TIMEOUT.
BOUND The DHCP client has done an initial binding to a new address.
The new IP address is passed in $new_ip_address, and the inter-
face name is passed in $interface. Any options acquired from
the server are passed using the option name described in
dhcp-options(5), except that dashes (`-') are replaced by
underscores (`_') in order to make valid shell variables, and
the variable names start with new_. So for example, the new
subnet mask would be passed in $new_subnet_mask.
When a binding has been completed, a lot of network parameters
are likely to need to be set up. A new /etc/resolv.conf needs
to be created, using the values of $new_domain_name and
$new_domain_name_servers (which may list more than one server,
separated by spaces). A default route should be set using
$new_routers, and static routes may need to be set up using
Note: since dhclient-script effectively overwrites
/etc/resolv.conf, any information contained therein is lost.
If options must be passed to the resolver, they may be con-
tained in /etc/resolv.conf.tail, which is appended to the gen-
erated /etc/resolv.conf by dhclient-script.
RENEW When a binding has been renewed, the script is called as in
BOUND, except that in addition to all the variables starting
with $new_, there is another set of variables starting with
$old_. Persistent settings that may have changed need to be
deleted - for example, if a local route to the bound address is
being configured, the old local route should be deleted. If
the default route has changed, the old default route should be
deleted. If the static routes have changed, the old ones
should be deleted. Otherwise, processing can be done as with
REBIND The DHCP client has rebound to a new DHCP server. This can be
handled as with RENEW, except that if the IP address has
changed, the ARP table should be cleared.
REBOOT The DHCP client has successfully reacquired its old address
after a reboot. This can be processed as with BOUND.
EXPIRE The DHCP client has failed to renew its lease or acquire a new
one, and the lease has expired. The IP address must be relin-
quished, and all related parameters should be deleted, as in
RENEW and REBIND.
FAIL The DHCP client has been unable to contact any DHCP servers,
and any leases that have been tested have not proved to be
valid. The parameters from the last lease tested should be
deconfigured. This can be handled in the same way as EXPIRE.
TIMEOUT The DHCP client has been unable to contact any DHCP servers.
However, an old lease has been identified, and its parameters
have been passed in as with BOUND. The client configuration
script should test these parameters and, if it has reason to
believe they are valid, should exit with a value of zero. If
not, it should exit with a nonzero value.
The usual way to test a lease is to set up the network as with REBIND
(since this may be called to test more than one lease) and then ping the
first router defined in $routers. If a response is received, the lease
must be valid for the network to which the interface is currently con-
nected. It would be more complete to try to ping all of the routers
listed in $new_routers, as well as those listed in $new_static_routes,
but current scripts do not do this.
dhclient.conf(5), dhclient.leases(5), dhclient(8), dhcpd(8)
(net/isc-dhcp42-server), dhcrelay(8) (net/isc-dhcp42-relay)
The original version of dhclient-script was written for the Internet
Software Consortium by Ted Lemon <firstname.lastname@example.org> in cooperation with
The OpenBSD implementation of dhclient-script was written by Kenneth R.
If more than one interface is being used, there's no obvious way to avoid
clashes between server-supplied configuration parameters - for example,
the stock dhclient-script rewrites /etc/resolv.conf. If more than one
interface is being configured, /etc/resolv.conf will be repeatedly ini-
tialized to the values provided by one server, and then the other.
Assuming the information provided by both servers is valid, this
shouldn't cause any real problems, but it could be confusing.
DragonFly 5.1 August 4, 2012 DragonFly 5.1