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>
SEE ALSO¶
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