INETD(8)INETD(8)NAME
inetd - internet ``super-server''
SYNOPSIS
/usr/etc/inetd [ -d ] [ configuration file ]
DESCRIPTION
Inetd should be run at boot time by /etc/rc. 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 corresponds to,
and invokes a program to service the request. After the program 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.
An rpc server can be started from inetd. The only differences from the
usual code are that svcudp_create should be called as:
transp = svcudp_create(0)
since inet passes a socket file as descriptor 0, and svc_register
should be called as:
svc_register(transp, PROGNUM, VERSNUM, dispatch, 0)
with the final flag as 0, since the program will already have been
registered by inetd. If you want to exit from the server process and
return control to inet, you must explicitly exit since svc_run never
returns.
Upon execution, inetd reads its configuration information from a
configuration file which, by default, is /etc/inetd.conf. There must
be an entry for each field in 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. The fields of the configuration file
are as follows:
service name
socket type
protocol
wait/nowait
user
server program
server program arguments
For rpc services:
service name/version
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).
For RPC services the entry is the name of a valid service in the file
/etc/rpc with version = 1-x. An example might be ``mountd/1-2''
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.
Examples might be ``tcp'' or ``udp''.
For RPC services the protocol is of the form rcp/protocol. Examples
might be ``rpc/tcp'' or ``rpc/udp''.
The wait/nowait entry is applicable to datagram (and rpc) sockets only
(other sockets 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. ``Comsat'' (``biff'') and ``talk'' are both examples
of the latter type of datagram server. Tftpd 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
server 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 arguments to the server program should be just as they 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 midnight, January 1, 1900). All of these services are
tcp based. For details of these services, consult the appropriate RFC
from the Network Information 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.
EXAMPLES
#
# Standard inetd.conf entries
ftp stream tcp nowait root /etc/ftpd ftpd
talk dgram udp wait root /etc/talkd talkd
#
# RPC services entries
rexd/1 stream rpc/tcp wait root /usr/etc/rpc.rexd rpc.rexd
SEE ALSOcomsat(8C), ftpd(8C), rexecd(8C), rlogind(8C), rshd(8C), telnetd(8C),
tftpd(8C)4.3 Berkeley Distribution May 26, 1986 INETD(8)