--- /dev/null
+
+
+
+dhclient(8) dhclient(8)
+
+
+N\bNA\bAM\bME\bE
+ dhclient-script - DHCP client network configuration script
+
+D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
+ The DHCP client network configuration script is invoked
+ from time to time by d\bdh\bhc\bcl\bli\bie\ben\bnt\bt(\b(8\b8)\b). This script is used by
+ the dhcp client to set each interface's initial configura
+ tion prior to requesting an address, to test the address
+ once it has been offered, and to set the interface's final
+ configuration once a lease has been acquired. If no lease
+ is acquired, the script is used to test predefined leases,
+ if any, and also called once if no valid lease can be
+ identified.
+
+ This script is not meant to be customized by the end user.
+ However, the script may not work on particular versions of
+ particular operating systems (indeed, no standard script
+ exists for some operating systems), so a pioneering user
+ may well need to create a new script or modify an existing
+ one. In general, customizations specific to a particular
+ computer should be done in the /\b/e\bet\btc\bc/\b/d\bdh\bhc\bcl\bli\bie\ben\bnt\bt.\b.c\bco\bon\bnf\bf script.
+ If you find that you can't make such a customization with
+ out customizing dhclient.conf, please submit a bug report.
+
+O\bOP\bPE\bER\bRA\bAT\bTI\bIO\bON\bN
+ When dhclient needs to invoke the client configuration
+ script, it writes a shell script into /tmp which defines a
+ variety of variables. In all cases, $reason is set to the
+ name of the reason why the script has been invoked. The
+ following reasons are currently defined: MEDIUM, PREINIT,
+ ARPCHECK, ARPSEND, BOUND, RENEW, REBIND, REBOOT, EXPIRE,
+ FAIL and TIMEOUT.
+
+
+M\bME\bED\bDI\bIU\bUM\bM
+ The DHCP client is requesting that an interface's media
+ type be set. The interface name is passed in $interface,
+ and the media type is passed in $medium.
+
+P\bPR\bRE\bEI\bIN\bNI\bIT\bT
+ The DHCP client is requesting that an interface be config
+ ured as required in order to send packets prior to receiv
+ ing an actual address. For clients which use the BSD
+ socket library, this means configuring the interface with
+ an IP address of 0.0.0.0 and a broadcast address of
+ 255.255.255.255. For other clients, it may be possible
+ to simply configure the interface up without actually giv
+ ing it an IP address at all. The interface name is
+ passed in $interface, and the media type in $medium.
+
+ If an IP alias has been declared in dhclient.conf, its
+ address will be passed in $alias_ip_address, and that ip
+ alias should be deleted from the interface, along with any
+ routes to it.
+
+
+
+ 1
+
+
+
+
+
+dhclient(8) dhclient(8)
+
+
+A\bAR\bRP\bPS\bSE\bEN\bND\bD
+ The DHCP client is requesting that an address that has
+ been offered to it be checked to see if somebody else is
+ using it, by sending an ARP request for that address.
+ It's not clear how to implement this, so no examples exist
+ yet. The IP address to check is passed in
+ $new_ip_address, and the interface name is passed in
+ $interface.
+
+A\bAR\bRP\bPC\bCH\bHE\bEC\bCK\bK
+ The DHCP client wants to know if a response to the ARP
+ request send using ARPCHECK has been received. If one
+ has, the script should exit with a nonzero status, indi
+ cating that the offered address has already been requested
+ and should be declined. $new_ip_address and $interface
+ are set as with ARPSEND.
+
+B\bBO\bOU\bUN\bND\bD
+ 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. The media type is passed in $medium. Any
+ options acquired from the server are passed using the
+ option name described in d\bdh\bhc\bcp\bp-\b-o\bop\bpt\bti\bio\bon\bns\bs, 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 param
+ eters 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, seperated by spaces). A
+ default route should be set using $new_routers, and static
+ routes may need to be set up using $new_static_routes.
+
+ If an IP alias has been declared, it must be set up here.
+ The alias IP address will be written as $alias_ip_address,
+ and other DHCP options that are set for the alias (e.g.,
+ subnet mask) will be passed in variables named as
+ described previously except starting with $alias_ instead
+ of $new_. Care should be taken that the alias IP address
+ not be used if it is identical to the bound IP address
+ ($new_ip_address), since the other alias parameters may be
+ incorrect in this case.
+
+R\bRE\bEN\bNE\bEW\bW
+ 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
+
+
+
+ 2
+
+
+
+
+
+dhclient(8) dhclient(8)
+
+
+ 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.
+
+R\bRE\bEB\bBI\bIN\bND\bD
+ 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.
+
+R\bRE\bEB\bBO\bOO\bOT\bT
+ The DHCP client has successfully reacquired its old
+ address after a reboot. This can be processed as with
+ BOUND.
+
+E\bEX\bXP\bPI\bIR\bRE\bE
+ 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.
+
+F\bFA\bAI\bIL\bL
+ 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.
+
+T\bTI\bIM\bME\bEO\bOU\bUT\bT
+ 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.
+
+F\bFI\bIL\bLE\bES\bS
+ Each operating system should generally have its own script
+ file, although the script files for similar operating sys
+ tems may be similar or even identical. The script files
+ included in the Internet Software Consortium DHCP distri
+ bution appear in the distribution tree under
+ client/scripts, and bear the names of the operating
+
+
+
+ 3
+
+
+
+
+
+dhclient(8) dhclient(8)
+
+
+ systems on which they are intended to work.
+
+B\bBU\bUG\bGS\bS
+ If more than one interface is being used, there's no obvi
+ ous way to avoid clashes between server-supplied configu
+ ration 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.
+
+S\bSE\bEE\bE A\bAL\bLS\bSO\bO
+ dhclient(8), dhcpd(8), dhcrelay(8), dhclient.conf(5) and
+ dhclient.leases(5).
+
+A\bAU\bUT\bTH\bHO\bOR\bR
+ d\bdh\bhc\bcl\bli\bie\ben\bnt\bt-\b-s\bsc\bcr\bri\bip\bpt\bt(\b(8\b8)\b) has been written for the Internet Soft
+ ware Consortium by Ted Lemon <mellon@fugue.com> in cooper
+ ation with Vixie Enterprises. To learn more about the
+ Internet Software Consortium, see h\bht\btt\btp\bp:\b:/\b//\b/w\bww\bww\bw.\b.v\bvi\bix\bx.\b.c\bco\bom\bm/\b/i\bis\bsc\bc.\b.
+ To learn more about Vixie Enterprises, see
+ h\bht\btt\btp\bp:\b:/\b//\b/w\bww\bww\bw.\b.v\bvi\bix\bx.\b.c\bco\bom\bm.\b.
+
+
+
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+
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+ 4
+
+
projects / thirdparty / dhcp.git / commitdiff
