NAME

inetd − internet super-server

SYNOPSIS

/etc/inetd [ −d ] [ configuration file ]

DESCRIPTION

inetd should be run at boot time by /etc/rc2.d/S30tcp. 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. 

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 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, except as noted below.  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). For RPC services, the value of the service name field consists of the RPC service name, followed by a slash (/) and either a version number or a range of version numbers (for example, mountd/1).

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 field consists of the string “rpc” followed by a slash (/) and the name of the protocol (for example, rpc/udp).

The wait/nowait entry is applicable to datagram 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. 

FILES

/etc/inetd.conf
/etc/services
/etc/protocols

SEE ALSO

ftpd(8C), rlogind(8C), rshd(8C), telnetd(8C), tftpd(8C)

September 02, 1992