bootpd, bootpgw - Internet Boot Protocol server/gateway
bootpd [ -i -s -t timeout -d level -c chdir-path ] [ bootptab [ dumpfile ] ]
bootpgw [ -i -s -t timeout -d level ] server
Bootpd implements an Internet Bootstrap Protocol (BOOTP) server as defined in RFC951,
RFC1532, and RFC1533. Bootpgw implements a simple BOOTP gateway which can be used to for-
ward 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).
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 par-
ticularly 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 bootpgw 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).
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 minutes,
then the program will exit. A timeout value of zero means "run forever". In
standalone mode, this option is forced to zero.
Sets the debug-level variable that controls the amount of debugging messages gener-
ated. For example, -d4 or -d 4 will set the debugging level to 4. For compatibil-
ity with older versions of bootpd, omitting the numeric parameter (i.e. just -d)
will simply increment the debug level by one.
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.
Specifies the name of the configuration file from which bootpd loads its database
of known clients and client options (bootpd only).
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).
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 pro-
vided 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 indi-
cate that the client has been waiting for at least three seconds.
When bootpd is started it reads a configuration file, (normally /etc/bootptab) that ini-
tializes the internal database of known clients and client options. This internal data-
base is reloaded from the configuration file when bootpd receives a hangup signal (SIGHUP)
or when it discovers that the configuration file has changed.
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 /etc/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 (which normally uses /etc/services). Two service names (and port numbers)
bootps - BOOTP Server listening port
bootpc - BOOTP Client destination port
If the port numbers cannot be determined using getservbyname then the values default to
bootps=67 and bootpc=68.
/etc/bootptab Database file read by bootpd.
/etc/bootpd.dump Debugging dump file created by bootpd.
/etc/services Internet service numbers.
/tftpboot Current directory typically used by the TFTP server and bootpd.
Individual host entries must not exceed 1024 characters.
This distribution is currently maintained by Walter L. Wimer email@example.com.
The original BOOTP server was created by Bill Croft at Stanford University in January
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 firstname.lastname@example.org
John Brezak email@example.com
Frank da Cruz firstname.lastname@example.org
David R. Linn email@example.com
Jim McKim firstname.lastname@example.org
Gordon W. Ross email@example.com
Jason Zions firstname.lastname@example.org
bootptab(5), inetd(8), tftpd(8)
DARPA Internet Request For Comments:
RFC951 Bootstrap Protocol
RFC1532 Clarifications and Extensions for the Bootstrap Protocol
RFC1533 DHCP Options and BOOTP Vendor Extensions
Carnegie Mellon University November 06, 1993 BOOTPD(8)