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 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).
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 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).
- -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 minutes, 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.
- bootptab
- Specifies the name of the configuration file from which bootpd
loads its database of known clients and client options (bootpd
only).
- 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).
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.
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) 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 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
<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>
Gordon W. Ross <gwr@mc.com>
Jason Zions <jazz@hal.com>
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