bootpd, bootpgw - Internet Boot Protocol server/gateway
bootpd [ -v ] [ -i -s -t timeout -d level -c chdir-path ] [ bootptab [
dumpfile ] ]
bootpgw [ -v ] [ -i -s -t timeout -d level ] server
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
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
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
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.
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.
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
-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.
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.
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 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
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 >
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.
Database file read by bootpd.
Debugging dump file created by bootpd.
Internet service numbers.
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
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 <email@example.com>
John Brezak <firstname.lastname@example.org>
Frank da Cruz <email@example.com>
David R. Linn <firstname.lastname@example.org>
Jim McKim <email@example.com>
Pauline Middelink <firstname.lastname@example.org>
Martin Schulze <email@example.com>
Gordon W. Ross <firstname.lastname@example.org>
Jason Zions <email@example.com>
bootptab(5), services(5), inetd(8), inetd.conf(5), 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