Ubuntu Manpage: bootpd, bootpgw - Internet Boot Protocol server/gateway

NAME

       bootpd, bootpgw - Internet Boot Protocol server/gateway

SYNOPSIS

       bootpd [ -v ] [ -i -s -t timeout -d level -c chdir-path ] [ bootptab [ dumpfile ] ]
       bootpgw [ -v ] [ -i -s -t timeout -d level ] server

DESCRIPTION

Bootpd implements an Internet Bootstrap Protocol (BOOTP) server as defined in RFC951, RFC1532, and
RFC1533. This server also provides some extension to support the static part of Dynamic Host
Configuration Protocol (DHCP) as specified in RFC1533. DHCP is used by Windows NT and 95. Bootpgw
implements a simple BOOTP gateway which can be used to forward requests and responses between clients on
one subnet and a BOOTP server (i.e. bootpd) on another subnet. While either bootpd or bootpgw will
forward BOOTREPLY packets, only bootpgw will forward BOOTREQUEST packets.

One host on each network segment is normally configured to run either bootpd or bootpgw from inetd by
including one of the following lines in the file /etc/inetd.conf:

bootps dgram udp wait root /usr/sbin/bootpd bootpd bootptab
bootps dgram udp wait root /usr/sbin/bootpgw bootpgw server

This mode of operation is referred to as "inetd mode" and causes bootpd (or bootpgw) to be started only
when a boot request arrives. If it does not receive another packet within fifteen minutes of the last
one it received, it will exit to conserve system resources. The -t option controls this timeout (see
OPTIONS below).

It is also possible to run bootpd (or bootpgw) in "standalone mode" (without inetd) by simply invoking it
from a shell like any other regular command. Standalone mode is particularly useful when bootpd is used
with a large configuration database, where the start up delay might otherwise prevent timely response to
client requests. (Automatic start up in standalone mode can be done by invoking bootpd from within
/etc/rc.local, for example.) Standalone mode is less useful for bootgw which has very little start up
delay because it does not read a configuration file.

Either program automatically detects whether it was invoked from inetd or from a shell and automatically
selects the appropriate mode. The -s or -i option may be used to force standalone or inetd mode
respectively (see OPTIONS).

OPTIONS

-t timeout
Specifies the timeout value (in minutes) that a bootpd or bootpgw process will wait for a BOOTP
packet before exiting. If no packets are received for timeout seconds, then the program will
exit. A timeout value of zero means "run forever". In standalone mode, this option is forced to
zero.

-d debug-level
Sets the debug-level variable that controls the amount of debugging messages generated. For
example, -d4 or -d 4 will set the debugging level to 4. For compatibility with older versions of
bootpd, omitting the numeric parameter (i.e. just -d) will simply increment the debug level by
one.

-c chdir-path
Sets the current directory used by bootpd while checking the existence and size of client boot
files. This is useful when client boot files are specified as relative pathnames, and bootpd
needs to use the same current directory as the TFTP server (typically /tftpboot). This option is
not recognized by bootpgw.

-i Force inetd mode. This option is obsolete, but remains for compatibility with older versions of
bootpd.

-s Force standalone mode. This option is obsolete, but remains for compatibility with older versions
of bootpd.

-v Print version and exit.

bootptab
Specifies the name of the configuration file from which bootpd loads its database of known clients
and client options (bootpd only). Default is /etc/bootptab.

dumpfile
Specifies the name of the file that bootpd will dump its internal database into when it receives a
SIGUSR1 signal (bootpd only). This option is only recognized if bootpd was compiled with the
-DDEBUG flag.

server Specifies the name of a BOOTP server to which bootpgw will forward all BOOTREQUEST packets it
receives (bootpgw only).

OPERATION

Both bootpd and bootpgw operate similarly in that both listen for any packets sent to the bootps port,
and both simply forward any BOOTREPLY packets. They differ in their handling of BOOTREQUEST packets.

When bootpgw is started, it determines the address of a BOOTP server whose name is provided as a command
line parameter. When bootpgw receives a BOOTREQUEST packet, it sets the "gateway address" and "hop
count" fields in the packet and forwards the packet to the BOOTP server at the address determined
earlier. Requests are forwarded only if they indicate that the client has been waiting for at least
three seconds.

When bootpd is started it reads a configuration file, (normally /etc/bootptab) that initializes the
internal database of known clients and client options. This internal database is reloaded from the
configuration file when bootpd receives a hangup signal (SIGHUP) or when it discovers that the
configuration file has changed. Note that any changes to the configuration file should be atomic to
avoid race conditions.

When bootpd receives a BOOTREQUEST packet, it looks for a database entry matching the client request. If
the client is known, bootpd composes a BOOTREPLY packet using the database entry found above, and sends
the reply to the client (possibly using a gateway). If the client is unknown, the request is discarded
(with a notice if debug > 0).

If bootpd is compiled with the -DDEBUG option, receipt of a SIGUSR1 signal causes it to dump its internal
database to the file /tmp/bootpd.dump or the dumpfile specified as a command line parameter.

During initialization, both programs determine the UDP port numbers to be used by calling
getservbyname(3) (which normally uses /etc/services). Two service names (and port numbers) are used:

bootps - BOOTP Server listening port
bootpc - BOOTP Client destination port

If the port numbers cannot be determined using getservbyname then the values default to boopts=67 and
bootpc=68.

FILES

       /etc/bootptab
              Database file read by bootpd.

       /tmp/bootpd.dump
              Debugging dump file created by bootpd.

       /etc/services
              Internet service numbers.

       /tftpboot
              Current directory typically used by the TFTP server and bootpd.

BUGS

       Individual host entries must not exceed 1024 characters.

CREDITS

       This distribution is currently maintained by Walter L. Wimer <walt+@cmu.edu>.

       The original BOOTP server was created by Bill Croft at Stanford University in January 1986.

       The current version of bootpd is primarily the work of David Kovar, Drew D. Perkins, and Walter L. Wimer,
       at Carnegie Mellon University.

       Enhancements and bug-fixes have been contributed by:
              (in alphabetical order)
              Danny Backx <db@sunbim.be>
              John Brezak <brezak@ch.hp.com>
              Frank da Cruz <fdc@cc.columbia.edu>
              David R. Linn <drl@vuse.vanderbilt.edu>
              Jim McKim <mckim@lerc.nasa.gov>
              Pauline Middelink <middelin@calvin.polyware.iaf.nl>
              Martin Schulze <joey@infodrom.north.de>
              Gordon W. Ross <gwr@mc.com>
              Jason Zions <jazz@hal.com>