inetd
NAME
SYNOPSIS
DESCRIPTION
should be run at boot time by
(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,
allows running one daemon to invoke several others,
reducing load on the system.
The options are as follows:
- d Turns on debugging.
- E Prevents from laundering the environment. Without this option a selection of environent variables believed by the authors to be harmful, including
will be removed and not inherited by services.
l
Turns on libwrap connection logging. Internal services cannot be wrapped.
When enabled,
is silently not executed even if present in
Upon execution,
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:
service name socket type protocol[,sndbuf=size][,rcvbuf=size] wait/nowait[.max] user[.group] or user[:group] server program server program arguments
To specify a Sun-RPC
based service, the entry would contain these fields.
service name/version socket type rpc/protocol[,sndbuf=size][,rcvbuf=size] wait/nowait[.max] user[.group] or user[:group] server program 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 address
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
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
this value is ignored.
The
entry is the name of a valid service in
the file
For
services (discussed below), the service
name
be the official name of the service (that is, the first entry in
When used to specify a Sun-RPC
based service, this field is a valid RPC service name in
the file
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 -
For
domain sockets this field specifies the path name of the socket.
The
should be one of
or
depending on whether the socket is a stream, datagram, raw,
reliably delivered message, or sequenced packet socket.
The
must be a valid protocol as given in
Examples might be
or
RPC based services are specified with the
or
service type.
and
will be recognized as
This is currently IPv4, but in the future it will be IPv6.
If you need to specify IPv4 or IPv6 explicitly, use something like
or
A
of
is used to specify a socket in the
domain.
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
as the window scale factor, which is based on the receive socket
buffer size, is advertised when the connection handshake occurs,
thus the socket buffer size for the server must be set on the listen socket.
By increasing the socket buffer sizes, better
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
to indicate kilobytes or
to indicate megabytes.
The
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
can receive further messages on the socket, it is said to be
a
server, and should use the
entry.
For datagram servers which process all incoming datagrams
on a socket and eventually time out, the server is said to be
and should use a
entry.
comsat(8)
and
talkd(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
in order to avoid a race;
the server reads the first packet, creates a new socket,
and then forks and exits to allow
to check for new service requests to spawn new servers.
The optional
suffix (separated from
or
by a dot) specifies the maximum number of server instances that may be
spawned from
within an interval of 60 seconds.
When omitted,
defaults to 256.
Stream servers are usually marked as
but if a single server process is to handle multiple connections, it may be
marked as
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.
The
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
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
The
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
should take the place of this entry.
provides several
services internally by use of routines within itself.
These services are
(character generator),
(human readable time), and
(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
from the Network Information Center.
rereads its configuration file when it receives a hangup signal,
Services may be added, deleted or modified when the configuration file
is reread.
creates a file
that contains its process identifier.
Support for
wrappers is included with
to provide built-in tcpd-like access control functionality.
An external tcpd program is not needed.
You do not need to change the
server-program entry to enable this capability.
uses
and
for access control facility configurations, as described in
hosts_access(5)
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
for
and
Under various combinations of IPv4/v6 daemon settings,
will behave as follows:
- t
If you have only one server on
IPv4 traffic will be routed to the server.
IPv6 traffic will not be accepted.
t
If you have two servers on
and
IPv4 traffic will be routed to the server on
and IPv6 traffic will go to server on
t
If you have only one server on
only IPv6 traffic will be routed to the server.
The special
parameter can be used for obsolete servers which require to receive IPv4
connections mapped in an IPv6 socket. Its usage is discouraged.
SEE ALSO
HISTORY
The
command appeared in
x 4.3 .
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.
Marco d'Itri ported this code from OpenBSD in summer 2002 and added
socket buffers tuning and libwrap support from the NetBSD source tree.
BUGS
On Linux systems, the daemon cannot reload its configuration and needs
to be restarted when the host address for a service is changed between
and a specific address.
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.)
on IPv6 is not tested enough.
Kerberos support on IPv6 is not tested.
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