118 lines
3.4 KiB
Groff
118 lines
3.4 KiB
Groff
.TH TCPD 8
|
|
.SH NAME
|
|
tcpd, tcpdp \- waits for a TCP connection request and starts a server
|
|
.SH SYNOPSIS
|
|
.B tcpd
|
|
.RB [ \-d ]
|
|
.RB [ \-m
|
|
.RI maxclients ]
|
|
.RI service
|
|
.RI program
|
|
.RB [ arg ... ]
|
|
.SH DESCRIPTION
|
|
.de SP
|
|
.if t .sp 0.4
|
|
.if n .sp
|
|
..
|
|
.B Tcpd
|
|
is a daemon, that is, a user-space program that is normally started when the
|
|
operating system is started and that normally does not terminate until the
|
|
system is shut down.
|
|
Conceptually, you can think of
|
|
.B tcpd
|
|
as doing nothing but listening to a port for a connection attempt. Several
|
|
copies of
|
|
.B tcpd
|
|
will typically be started, one for each service that is to be provided.
|
|
When a connection is detected the tcpd for that port
|
|
.IR fork s
|
|
and then the child process
|
|
.IR exec s
|
|
an instance of the server for that port.
|
|
.P
|
|
The above description is simplified.
|
|
Normally two versions of the tcpd.c source code are compiled.
|
|
.B Tcpd
|
|
is the one that waits for a connection. When a connection occurs
|
|
.B tcpd
|
|
.IR fork s.
|
|
If
|
|
.B tcpd
|
|
was started with options or if the child detects that the access
|
|
control file
|
|
.IR /etc/serv.access
|
|
exists, the child will
|
|
.IR exec
|
|
its paranoid twin,
|
|
.B tcpdp,
|
|
which checks that the connection attempt is from an allowed node or network,
|
|
or that it is not from a disallowed node or network.
|
|
.B Tcpdp
|
|
also tries to look up the name corresponding to an IP address, and denies
|
|
the connection if a name cannot be found. Finally,
|
|
.B tcpdp
|
|
determines whether the connection is supposed to be logged.
|
|
If all is well, the child
|
|
.B tcpd
|
|
or
|
|
.B tcpdp
|
|
then
|
|
.IR exec s
|
|
the server for the service with any arguments specified on the command line
|
|
for that server.
|
|
.SH OPTIONS
|
|
.TP
|
|
.B \-d
|
|
turn on debugging.
|
|
.TP
|
|
.B \-m
|
|
allow no more than the specified
|
|
.IR maxclients
|
|
to start.
|
|
.SH EXAMPLES
|
|
.de EX
|
|
.TP 20
|
|
\\fB\\$1\\fR
|
|
# \\$2
|
|
..
|
|
.TP 15n
|
|
.EX "tcpd telnet in.telnetd &" "wait for a telnet connection on the normal port"
|
|
.EX "tcpd 8000 in.httpd /etc/httpd8000.conf &" "wait for web page request on port 8000 and use a custom config file for the in.httpd program."
|
|
.P
|
|
Note that command lines must be terminated with "&" to return control to the
|
|
calling process, leaving the daemon executing as a background process.
|
|
.P
|
|
The above examples show how tcpd might be invoked from /etc/rc or
|
|
another script that runs during system initialization. You will also
|
|
see this in the supplied startup scripts:
|
|
.EX "daemonize tcpd shell in.rshd" "daemonize is a shell function that tests whether a daemon is present and starts it if so, using the & to start it in the background."
|
|
.P
|
|
Another case that should be mentioned is that when a system administrator
|
|
wants to start (or restart) a daemon from a command line,
|
|
.BR intr (8)
|
|
should be used, like this:
|
|
.EX "intr -d tcpd telnet in.telnetd &" "remove the daemon from a process group and connect its input to /dev/null and its output to /dev/log."
|
|
.SH FILES
|
|
.TP 25n
|
|
.B /etc/serv.access
|
|
The access control file.
|
|
.SH "SEE ALSO"
|
|
.BR execve (2),
|
|
.BR fork (2),
|
|
.BR intr (8),
|
|
.BR serv.access (5).
|
|
.SH NOTES
|
|
That daemons cannot daemonize themselves is a way in which Minix differs from
|
|
most other Unix-like systems.
|
|
.P
|
|
Allowing access to your system from the net is dangerous. Be sure you
|
|
know what you are doing. Be sure the owner of your net knows what you are
|
|
doing. Don't enable services you don't need. Enable logging and look at your
|
|
logs.
|
|
.SH BUGS
|
|
None known, let us know...
|
|
.SH AUTHOR
|
|
Kees J. Bot <kjb@cs.vu.nl>
|
|
.P
|
|
Man page by Al Woodhull <asw@woodhull.com>
|
|
.\" rev 2006-06-02
|