--- embedaddon/dhcp/client/dhclient.8 2012/02/21 22:30:18 1.1 +++ embedaddon/dhcp/client/dhclient.8 2012/10/09 09:06:54 1.1.1.1 @@ -1,6 +1,6 @@ -.\" $Id: dhclient.8,v 1.1 2012/02/21 22:30:18 misho Exp $ +.\" $Id: dhclient.8,v 1.1.1.1 2012/10/09 09:06:54 misho Exp $ .\" -.\" Copyright (c) 2004,2007-2011 by Internet Systems Consortium, Inc. ("ISC") +.\" Copyright (c) 2004,2007-2012 by Internet Systems Consortium, Inc. ("ISC") .\" Copyright (c) 1996-2003 by Internet Software Consortium .\" .\" Permission to use, copy, modify, and distribute this software for any @@ -134,8 +134,8 @@ fail, by statically assigning an address. .PP The DHCP protocol allows a host to contact a central server which maintains a list of IP addresses which may be assigned on one or more -subnets. A DHCP client may request an address from this pool, and -then use it on a temporary basis for communication on network. The +subnets. A DHCP client may request an address from this pool, and +then use it on a temporary basis for communication on network. The DHCP protocol also provides a mechanism whereby a client can learn important details about the network to which it is attached, such as the location of a default router, the location of a name server, and @@ -149,20 +149,19 @@ or options. .PP On startup, \fBdhclient\fR reads the dhclient.conf -.IR dhclient.conf -for configuration instructions. It then gets a list of all the -network interfaces that are configured in the current system. For +for configuration instructions. It then gets a list of all the +network interfaces that are configured in the current system. For each interface, it attempts to configure the interface using the DHCP protocol. .PP In order to keep track of leases across system reboots and server restarts, \fBdhclient\fR keeps a list of leases it has been assigned in the -dhclient.leases file. On startup, after reading the dhclient.conf +dhclient.leases file. On startup, after reading the dhclient.conf file, \fBdhclient\fR reads the dhclient.leases file to refresh its memory about what leases it has been assigned. .PP When a new lease is acquired, it is appended to the end of the -dhclient.leases file. In order to prevent the file from becoming +dhclient.leases file. In order to prevent the file from becoming arbitrarily large, from time to time \fBdhclient\fR creates a new dhclient.leases file from its in-core lease database. The old version of the dhclient.leases file is retained under the name @@ -171,19 +170,19 @@ until the next time \fBdhclient\fR rewrites the databa .PP Old leases are kept around in case the DHCP server is unavailable when \fBdhclient\fR is first invoked (generally during the initial system boot -process). In that event, old leases from the dhclient.leases file +process). In that event, old leases from the dhclient.leases file which have not yet expired are tested, and if they are determined to be valid, they are used until either they expire or the DHCP server becomes available. .PP A mobile host which may sometimes need to access a network on which no DHCP server exists may be preloaded with a lease for a fixed -address on that network. When all attempts to contact a DHCP server +address on that network. When all attempts to contact a DHCP server have failed, \fBdhclient\fR will try to validate the static lease, and if it succeeds, will use that lease until it is restarted. .PP A mobile host may also travel to some networks on which DHCP is not -available but BOOTP is. In that case, it may be advantageous to +available but BOOTP is. In that case, it may be advantageous to arrange with the network administrator for an entry on the BOOTP database, so that the host can boot quickly on that network rather than cycling through the list of old leases. @@ -196,7 +195,7 @@ network interfaces, eliminating non-broadcast interfac possible, and attempt to configure each interface. .PP It is also possible to specify interfaces by name in the dhclient.conf -file. If interfaces are specified in this way, then the client will +file. If interfaces are specified in this way, then the client will only configure interfaces that are either specified in the configuration file or on the command line, and will ignore all other interfaces. @@ -259,7 +258,7 @@ DHCP client will exit if it isn't able to identify any to configure. On laptop computers and other computers with hot-swappable I/O buses, it is possible that a broadcast interface may be added after system startup. This flag can be used to cause the client -not to exit when it doesn't find any such interfaces. The +not to exit when it doesn't find any such interfaces. The .B omshell(1) program can then be used to notify the client when a network interface has been added or removed, so that the client can attempt to configure an IP @@ -397,28 +396,28 @@ client using TCP/IP, authenticate, and can then examin current status and make changes to it. .PP Rather than implementing the underlying OMAPI protocol directly, user -programs should use the dhcpctl API or OMAPI itself. Dhcpctl is a +programs should use the dhcpctl API or OMAPI itself. Dhcpctl is a wrapper that handles some of the housekeeping chores that OMAPI does -not do automatically. Dhcpctl and OMAPI are documented in +not do automatically. Dhcpctl and OMAPI are documented in \fBdhcpctl(3)\fR -and \fBomapi(3)\fR. Most things you'd want to do with the client can +and \fBomapi(3)\fR. Most things you'd want to do with the client can be done directly using the \fBomshell(1)\fR command, rather than having to write a special program. .SH THE CONTROL OBJECT The control object allows you to shut the client down, releasing all leases that it holds and deleting any DNS records it may have added. It also allows you to pause the client - this unconfigures any -interfaces the client is using. You can then restart it, which -causes it to reconfigure those interfaces. You would normally pause +interfaces the client is using. You can then restart it, which +causes it to reconfigure those interfaces. You would normally pause the client prior to going into hibernation or sleep on a laptop -computer. You would then resume it after the power comes back. +computer. You would then resume it after the power comes back. This allows PC cards to be shut down while the computer is hibernating or sleeping, and then reinitialized to their previous state once the computer comes out of hibernation or sleep. .PP -The control object has one attribute - the state attribute. To shut -the client down, set its state attribute to 2. It will automatically -do a DHCPRELEASE. To pause it, set its state attribute to 3. To +The control object has one attribute - the state attribute. To shut +the client down, set its state attribute to 2. It will automatically +do a DHCPRELEASE. To pause it, set its state attribute to 3. To resume it, set its state attribute to 4. .PP .SH ENVIRONMENT VARIABLES @@ -465,7 +464,7 @@ Stanford. The current version owes much to Elliot's Linux enhancements, but was substantially reorganized and partially rewritten by Ted Lemon so as to use the same networking framework that the Internet Systems -Consortium DHCP server uses. Much system-specific configuration code +Consortium DHCP server uses. Much system-specific configuration code was moved into a shell script so that as support for more operating systems is added, it will not be necessary to port and maintain system-specific configuration code to these operating systems - instead,