man.bsd.lv manual page server

DESCRIPTION

The options available for inetd:

-d

Turns on debugging.

-l

Turns on libwrap connection logging.

Upon execution, inetd reads its configuration information from a configuration file which, by default, is /etc/inetd.conf. The path given for this configuration file must be absolute, unless the -d option is also given on the command line. 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 for one special case, described below). The fields of the configuration file are as follows:

[listen-addr:]service-spec
socket-type[:accept-filter]
protocol[,sndbuf=size][,rcvbuf=size]
wait/nowait[:max]
user[:group]
server-program
server program arguments

The listen-addr specifies the local address inetd should use when listening. The single character “*” means INADDR_ANY: all local addresses. To avoid the need to repeat listen addresses over and over again, listen addresses are inherited from line to line, and the listen address can be changed without defining a service by including a line containing just a listen-addr followed by a colon. The default (compatible with historical configuration files) is *. To return to this behavior after configuring some services with specific listen addresses, give * explicitly.

Note that restricted listen addresses are meaningless and ignored for UNIX-domain services, and are not supported for Sun-RPC services. All Sun-RPC services always listen on all interfaces.

The form of the service-spec varies with the service type. For Internet services, the service-spec can be either the name of a service from /etc/services or a decimal port number. For “internal” services (discussed below), the service name must be the official name of the service (that is, the first entry in /etc/services) and not an alias for it.

For Sun-RPC based services, the service-spec has the form service-name/version. The service name must be a valid RPC service name from the file /etc/rpc. The version on the right of the “/” is the RPC version number. This can simply be a single numeric argument or a range of versions. A range is bounded by the low version to the high version - e.g. “rusers/1-3”.

For UNIX-domain (local) services, the service-spec is the path name to listen on.

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.

Optionally, for Internet services, an accept filter (see accept_filter(9)) can be specified by appending a colon to socket-type, followed by the name of the desired accept filter. In this case inetd will not see new connections for the specified service until the accept filter decides they are ready to be handled.

The protocol must be a valid protocol as given in /etc/protocols or (for UNIX-domain services) the string “unix”. The most common are “tcp” and “udp”. For TCP and UDP, the IP version (4 or 6) may be specified explicitly by appending 4 or 6 to the protocol name. Otherwise the default version (IPv4) is used. For Sun-RPC the string “rpc” and a slash should be prepended: “rpc/tcp” or “rpc/udp”. If you would like to enable special support for faithd(8), prepend the string “faith” and a slash: “faith/tcp6”.

In addition to the protocol, the configuration file may specify the send and receive socket buffer sizes for the listening socket. This is especially useful for TCP: the window scale factor, which is based on the receive socket buffer size, is advertised when the connection handshake occurs and thus the socket buffer size must be set on the listen socket. By increasing the socket buffer sizes, better TCP performance may be realized in some situations. The socket buffer sizes are specified by appending their values to the protocol specification as follows:

tcp,rcvbuf=16384
tcp,sndbuf=64k
tcp,rcvbuf=64k,sndbuf=1m

A literal value may be specified, or modified using ‘k’ to indicate kilobytes or ‘m’ to indicate megabytes. Socket buffer sizes may be specified for all services and protocols except for tcpmux services.

The wait/nowait entry is used to tell inetd if 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 inetd can 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 ntalkd(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 optional “max” suffix (separated from “wait” or “nowait” by a dot or a colon) specifies the maximum number of server instances that may be spawned from inetd within an interval of 60 seconds. When omitted, “max” defaults to 40. If it reaches this maximum spawn rate, inetd will log the problem (via the syslogger using the LOG_DAEMON facility and LOG_ERR level) and stop handling the specific service for ten minutes.

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. inetd will continue to listen on the master socket for connections, so the server should not close it when it exits. identd(8) is usually the only stream server marked as wait.

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. Optionally, a group can be specified by appending a colon to the user name, followed by the group name (it is possible to use a dot (``.'') in lieu of a colon, however this feature is provided only for backward compatibility). 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 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. It is possible to quote an argument using either single or double quotes. This allows you to have, e.g., spaces in paths and parameters.