|INETD(8)||System Manager's Manual||INETD(8)|
inetdshould be run at boot time by /etc/rc (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 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,
inetdallows running one daemon to invoke several others, reducing load on the system. The options are as follows:
inetdwill log the problem and stop servicing requests for the specific service for ten minutes. See also the wait/nowait configuration fields below.
inetdreads 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. The fields of the configuration file are as follows:
service name socket type protocol wait/nowait[.max] user[.group] or user[:group] server program server program arguments
service name/version socket type rpc/protocol wait/nowait[.max] user[.group] or user[:group] server program server program arguments
inetdshould use when listening for that service. Multiple local addresses can be specified on the same line, separated by commas. Numeric IP addresses in dotted-quad notation can be used as well as symbolic hostnames. Symbolic hostnames are looked up using
getaddrinfo(). If a hostname has multiple address mappings, inetd creates a socket to listen on each address. The single character “*” indicates
INADDR_ANY, meaning “all local addresses”. To avoid repeating an address that occurs frequently, a line with a host address specifier and colon, but no further fields, causes the host address specifier to be remembered and used for all further lines with no explicit host specifier (until another such line or the end of the file). A line
inetdif it should wait for the server program to return, or continue processing connections on the socket. If a datagram server connects to its peer, freeing the socket so
inetdcan receive 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(8) (biff(1)) and talkd(8) are both examples of the latter type of datagram server. The optional “max” suffix (separated from “wait” or “nowait” by a dot) specifies the maximum number of times a service can be invoked in one minute; the default is 256. If a service exceeds this limit,
inetdwill log the problem and stop servicing requests for the specific service for ten minutes. See also the
-Roption above. Stream servers are usually marked as “nowait” but if a single server process is to handle multiple connections, it may be marked as “wait”. The master socket will then be passed as fd 0 to the server, which will then need to accept the incoming connection. The server should eventually time out and exit when no more connections are active.
inetdwill continue to listen on the master socket for connections, so the server should not close it when it exits. 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. An optional group name can be specified by appending a dot to the user name followed by the group name. This allows for servers to run with a different (primary) group ID than specified in the password file. If a group is specified and user is not root, the supplementary groups associated with that user will still be set. The server program entry should contain the pathname of the program which is to be executed by
inetdwhen a request is found on its socket. If
inetdprovides this service internally, this entry should be “internal”. The server program arguments should be just as arguments normally are, starting with argv, which is the name of the program. If the service is provided internally, the word “internal” should take the place of this entry.
inetdprovides 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.
inetdrereads its configuration file when it receives a hangup signal,
SIGHUP. Services may be added, deleted or modified when the configuration file is reread. inetd.conf, for “tcp4” and “tcp6”. Under various combinations of IPv4/v6 daemon settings,
inetdwill behave as follows:
inetdcommand appeared in 4.3BSD. Support for Sun-RPC based services is modelled after that provided by SunOS 4.1. IPv6 support was added by the KAME project in 1999.
|October 4, 2017||OpenBSD-current|