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