File: inetutils.info,  Node: Configuration file,  Next: Built-in services,  Prev: Invocation,  Up: inetd invocation

19.2 Configuration file
=======================

Upon execution, inetd reads its configuration information from
configuration files and directories named on the command line.  By
default these are '/etc/inetd.conf' and '/etc/inetd.d'.  If the
configuration pathname is a directory, all files in the directory are
read and interpreted like a configuration file.  All of the
configuration files are read and the results are merged.

   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 available fields of
the configuration file are summarized in the table below (optional parts
are enclosed in square brackets):

[service node:]service name
     The service-name entry is the name of a valid service in the file
     '/etc/services'.  For "internal" services (*note Built-in
     services::), the service name must be the official name of the
     service (that is, the first entry in '/etc/services'), or a numeric
     representation thereof.  For TCPMUX services, the value of the
     'service name' field consists of the string 'tcpmux' followed by a
     slash and the locally-chosen service name (*note TCPMUX::).

     An optional 'service node' prefix is allowed for internet services.
     When present, it supplies the local addresses 'inetd' should use
     when listening for that service.  'Service node' consists of a
     comma-separated list of addresses.  Both symbolic host names and
     numeric IP addresses are allowed.  Symbolic hostnames are looked up
     in DNS service.  If a hostname has multiple address mappings,
     'inetd' creates a socket to listen on each address.

     To avoid repeating an address that occurs frequently, a line with a
     host address specifier and colon, but no further fields is allowed,
     e.g.:

          127.0.0.1,192.168.0.5:

     The address specifier from such a line is remembered and used for
     all further lines lacking an explicit host specifier.  Such a
     default address remains in effect until another such line or end of
     the configuration is encountered, whichever occurs first.

     A special hostname '*' stands for the wildcard address.  When used
     in a normal configuration line, it causes the default address
     specifier to be ignored for that line.  When used in a default
     address specification, e.g.:

          *:

     it causes any previous default address specifier to be forgotten.

socket type
     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.  TCPMUX services must use 'stream'.

protocol
     The protocol must be a valid protocol as given in '/etc/protocols'.
     Examples might be 'tcp' or 'udp'.  TCPMUX services must use 'tcp'.
     If IPv6 support is enabled the sockets will accept both IPv4 and
     IPv6 connections if that is supported by the OS. If inetd should
     only accept IPv4 or IPv6 connections, add '4' or '6' to the
     protocol name.  For example 'tcp4' will only accept IPv4 tcp
     connections and 'udp6' will only accept IPv6 udp connections.

wait/nowait[.max]
     The 'wait/nowait' entry specifies whether the server that is
     invoked by 'inetd' will take over the socket associated with the
     service access point, and thus whether inetd should wait for the
     server to exit before listening for new service requests.  Datagram
     servers must use 'wait', as they are always invoked with the
     original datagram socket bound to the specified service address.
     These servers must read at least one datagram from the socket
     before exiting.  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; it should read one
     datagram from the socket and create a new socket connected to the
     peer.  It should fork, and the parent should then exit to allow
     inetd to check for new service requests to spawn new servers.
     Datagram servers which process all incoming datagrams on a socket
     and eventually time out are said to be "single-threaded".  'comsat'
     and 'talkd' are both examples of the latter type of datagram
     server.  'tftpd' is an example of a multi-threaded datagram server.

     Servers using stream sockets generally are multi-threaded and use
     the 'nowait' entry.  Connection requests for these services are
     accepted by inetd, and the server is given only the newly-accepted
     socket connected to a client of the service.  Most stream-based
     services and all TCPMUX services operate in this manner.  For such
     services, the number of running instances of the server can be
     limitied by specifying optional 'max' suffix (a decimal number),
     e.g.: 'nowait.15'.

     Stream-based servers that use 'wait' are started with the listening
     service socket, and must accept at least one connection request
     before exiting.  Such a server would normally accept and process
     incoming connection requests until a timeout.  Other services must
     use 'nowait'.

user
     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 form includes also a group name
     as a suffix, separated from the user name by colon or a period,
     i.e., 'user:group' or 'user.group'.

server program
     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'.

     It is common usage to specify '/usr/sbin/tcpd' in this field.

server program arguments
     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, this entry must contain the
     word 'internal', or be empty.