INETD(8) BSD System Manager's Manual INETD(8)
NAME
inetd - internet ``super-server''
SYNOPSIS
inetd [-d] [configuration file]
DESCRIPTION
Inetd should be run at boot time by /etc/rc.local (see rc(8)). It then
listens for connections on certain internet sockets. When a connection
is found on one of its sockets, it decides what service the socket corre-
sponds to, and invokes a program to service the request. After the pro-
gram is finished, it continues to listen on the socket (except in some
cases which will be described below). Essentially, inetd allows running
one daemon to invoke several others, reducing load on the system.
The option available for inetd:
-d Turns on debugging.
Upon execution, inetd reads its configuration information from a configu-
ration file which, by default, is /etc/inetd.conf. There must be an entry
for each field of the configuration file, with entries for each field
separated by a tab or a space. Comments are denoted by a ``#'' at the
beginning of a line. There must be an entry for each field. The fields
of the configuration file are as follows:
service name
socket type
protocol
wait/nowait
user
server program
server program arguments
The service-name entry is the name of a valid service in the file
/etc/services. For ``internal'' services (discussed below), the service
name must be the official name of the service (that is, the first entry
in /etc/services).
The socket-type should be one of ``stream'', ``dgram'', ``raw'', ``rdm'',
or ``seqpacket'', depending on whether the socket is a stream, datagram,
raw, reliably delivered message, or sequenced packet socket.
The protocol must be a valid protocol as given in /etc/protocols. Exam-
ples might be ``tcp'' or ``udp''.
The wait/nowait entry is applicable to datagram sockets only (other sock-
ets should have a ``nowait'' entry in this space). If a datagram server
connects to its peer, freeing the socket so inetd can received further
messages on the socket, it is said to be a ``multi-threaded'' server, and
should use the ``nowait'' entry. For datagram servers which process all
incoming datagrams on a socket and eventually time out, the server is
said to be ``single-threaded'' and should use a ``wait'' entry. Com-
sat(8) (biff(1)) and talkd(8) are both examples of the latter type of
datagram server. Tftpd(8) is an exception; it is a datagram server that
establishes pseudo-connections. It must be listed as ``wait'' in order
to avoid a race; the server reads the first packet, creates a new socket,
and then forks and exits to allow inetd to check for new service requests
to spawn new servers.
The user entry should contain the user name of the user as whom the serv-
er should run. This allows for servers to be given less permission than
root.
The server-program entry should contain the pathname of the program which
is to be executed by inetd when a request is found on its socket. If
inetd provides this service internally, this entry should be
``internal''.
The server program arguments should be just as arguments normally are,
starting with argv[0], which is the name of the program. If the service
is provided internally, the word ``internal'' should take the place of
this entry.
Inetd provides several ``trivial'' services internally by use of routines
within itself. These services are ``echo'', ``discard'', ``chargen''
(character generator), ``daytime'' (human readable time), and ``time''
(machine readable time, in the form of the number of seconds since mid-
night, January 1, 1900). All of these services are tcp based. For de-
tails of these services, consult the appropriate RFC from the Network In-
formation Center.
Inetd rereads its configuration file when it receives a hangup signal,
SIGHUP. Services may be added, deleted or modified when the configuration
file is reread.
SEE ALSO
comsat(8), fingerd(8), ftpd(8), rexecd(8), rlogind(8), rshd(8),
telnetd(8), tftpd(8)
HISTORY
The inetd command appeared in 4.3BSD.
4.3 Berkeley Distribution March 27, 1993 2