— internet super-server
should be run at boot time by
). 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).
allows running one daemon to
invoke several others, reducing load on the system.
The options are as follows:
- Turns on debugging.
- Specify the maximum number of times a service can be
invoked in one minute; the default is 256. If a service exceeds this
limit, inetd will log the problem and stop
servicing requests for the specific service for ten minutes. See also the
wait/nowait configuration fields below.
Upon execution, inetd
reads its configuration
information from a configuration file which, by default, is
. 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:
user[.group] or user[:group]
server program arguments
To specify a Sun-RPC based service, the entry would contain these fields.
user[.group] or user[:group]
server program arguments
For internet services, the first field of the line may also have a host address
specifier prefixed to it, separated from the service name by a colon. If this
is done, the string before the colon in the first field indicates what local
should 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
(). If a hostname has multiple address
mappings, inetd creates a socket to listen on each address.
The single character “*” indicates
, 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
is implicitly provided at the top of the file; thus, traditional configuration
files (which have no host address specifiers) will be interpreted in the
traditional manner, with all services listened for on all local addresses. If
the protocol is “unix”, this value is ignored.
The service name
entry is the name of a valid
service in the file /etc/services
“internal” services (discussed below), the service name
be the official name of the service (that
is, the first entry in /etc/services
). When used
to specify a Sun-RPC based service, this field is a valid RPC service name in
the file /etc/rpc
. The part 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 - “rusers/1-3”. For
-domain sockets this field specifies the path name
of the socket.
The socket type
should be one of
“stream” or “dgram”, depending on whether the
socket is a stream or datagram socket.
must be a valid protocol as given in
. Examples might be
“tcp” or “udp”. RPC based services are specified
with the “rpc/tcp” or “rpc/udp” service type.
“tcp” and “udp” will be recognized as “TCP
or UDP over default IP version”. This is currently IPv4, but in the
future it will be IPv6. If you need to specify IPv4 or IPv6 explicitly, use
something like “tcp4” or “udp6”. A
of “unix” is used to
specify a socket in the UNIX
entry is used to tell
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.
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,
will log the problem and stop servicing
requests for the specific service for ten minutes. See also the
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.
will continue to listen on the master
socket for connections, so the server should not close it when it exits.
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
when a request is found on its socket. If
provides 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.
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
rereads its configuration file when it
receives a hangup signal,
may be added, deleted or modified when the configuration file is reread.
If you wish to run a server for IPv4 and IPv6 traffic, you'll need to run two
separate processes for the same server program, specified as two separate
lines in inetd.conf
, for “tcp4” and
Under various combinations of IPv4/v6 daemon settings,
will behave as follows:
- If you have only one server on “tcp4”,
IPv4 traffic will be routed to the server. IPv6 traffic will not be
- If you have two servers on “tcp4” and
“tcp6”, IPv4 traffic will be routed to the server on
“tcp4”, and IPv6 traffic will go to server on
- If you have only one server on “tcp6”,
only IPv6 traffic will be routed to the server.
command appeared in
. Support for Sun-RPC based services is modelled
after that provided by SunOS 4.1. IPv6 support was added by the KAME project
Host address specifiers, while they make conceptual sense for RPC services, do
not work entirely correctly. This is largely because the portmapper interface
does not provide a way to register different ports for the same service on
different local addresses. Provided you never have more than one entry for a
given RPC service, everything should work correctly. (Note that default host
address specifiers do apply to RPC lines with no explicit specifier.)