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DHCLIENT-SCRIPT(8)     DragonFly System Manager's Manual    DHCLIENT-SCRIPT(8)

NAME
     dhclient-script -- DHCP client network configuration script

DESCRIPTION
     The DHCP client network configuration script is invoked from time to time
     by dhclient(8).

     In general, customizations specific to a particular computer should be
     done in the /etc/dhclient.conf file.

OPERATION
     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
               interface 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
               $new_static_routes.

               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
               contained in /etc/resolv.conf.tail, which is appended to the
               generated /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
               BOUND.

     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
               relinquished, 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
     connected.  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.

SEE ALSO
     dhclient.conf(5), dhclient.leases(5), dhclient(8), dhcpd(8)
     (net/isc-dhcp42-server), dhcrelay(8) (net/isc-dhcp42-relay)

AUTHORS
     The original version of dhclient-script was written for the Internet
     Software Consortium by Ted Lemon <mellon@fugue.com> in cooperation with
     Vixie Enterprises.

     The OpenBSD implementation of dhclient-script was written by Kenneth R.
     Westerback <krw@openbsd.org>.

BUGS
     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
     initialized 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 3.5                   August 4, 2012                   DragonFly 3.5