NAME¶
xinetd - the extended Internet services daemon
SYNOPSIS¶
xinetd [
options]
DESCRIPTION¶
xinetd performs the same function as
inetd: it starts programs
that provide Internet services. Instead of having such servers started at
system initialization time, and be dormant until a connection request arrives,
xinetd is the only daemon process started and it listens on all service
ports for the services listed in its configuration file. When a request comes
in,
xinetd starts the appropriate server. Because of the way it
operates,
xinetd (as well as
inetd) is also referred to as a
super-server.
The services listed in
xinetd's configuration file can be separated into
two groups. Services in the first group are called
multi-threaded and
they require the forking of a new server process for each new connection
request. The new server then handles that connection. For such services,
xinetd keeps listening for new requests so that it can spawn new
servers. On the other hand, the second group includes services for which the
service daemon is responsible for handling all new connection requests. Such
services are called
single-threaded and
xinetd will stop
handling new requests for them until the server dies. Services in this group
are usually datagram-based.
So far, the only reason for the existence of a super-server was to conserve
system resources by avoiding to fork a lot of processes which might be dormant
for most of their lifetime. While fulfilling this function,
xinetd
takes advantage of the idea of a super-server to provide features such as
access control and logging. Furthermore,
xinetd is not limited to
services listed in
/etc/services. Therefore, anybody can use
xinetd to start special-purpose servers.
OPTIONS¶
- -d
- Enables debug mode. This produces a lot of debugging output, and it makes
it possible to use a debugger on xinetd.
- -syslog syslog_facility
- This option enables syslog logging of xinetd-produced messages
using the specified syslog facility. The following facility names are
supported: daemon, auth, user, local[0-7]
(check syslog.conf(5) for their meanings). This option is
ineffective in debug mode since all relevant messages are sent to the
terminal.
- -filelog logfile
- xinetd-produced messages will be placed in the specified file.
Messages are always appended to the file. If the file does not exist, it
will be created. This option is ineffective in debug mode since all
relevant messages are sent to the terminal.
- -f config_file
- Determines the file that xinetd uses for configuration. The default
is /etc/xinetd.conf.
- -pidfile pid_file
-
The process ID is written to the file. This option is ineffective in debug
mode.
- -dontfork
- Tells xinetd to stay in the foreground rather than detaching itself, to
support being run from init or daemontools. This option automatically sets
-stayalive (see below).
- -stayalive
- Tells xinetd to stay running even if no services are specified.
- -limit proc_limit
- This option places a limit on the number of concurrently running processes
that can be started by xinetd. Its purpose is to prevent process
table overflows.
- -logprocs limit
- This option places a limit on the number of concurrently running servers
for remote userid acquisition.
- -version
- This option causes xinetd to print out its version information.
- -inetd_compat
- This option causes xinetd to read /etc/inetd.conf in addition to the
standard xinetd config files. /etc/inetd.conf is read after the standard
xinetd config files.
- -cc interval
- This option instructs xinetd to perform periodic consistency checks
on its internal state every interval seconds.
The
syslog and
filelog options are mutually exclusive. If none is
specified, the default is syslog using the
daemon facility. You should
not confuse
xinetd messages with messages related to service logging.
The latter are logged only if this is specified via the configuration file.
CONTROLLING XINETD¶
xinetd performs certain actions when it receives certain signals. The
actions associated with the specific signals can be redefined by editing
config.h and recompiling.
- SIGHUP
- causes a hard reconfiguration, which means that xinetd re-reads the
configuration file and terminates the servers for services that are no
longer available. Access control is performed again on running servers by
checking the remote location, access times and server instances. If the
number of server instances is lowered, some arbitrarily picked servers
will be killed to satisfy the limit; this will happen after any
servers are terminated because of failing the remote location or access
time checks. Also, if the INTERCEPT flag was clear and is set, any
running servers for that service will be terminated; the purpose of
this is to ensure that after a hard reconfiguration there will be
no running servers that can accept packets from addresses that do
not meet the access control criteria.
- SIGQUIT
- causes program termination.
- SIGTERM
- terminates all running servers before terminating xinetd.
- SIGUSR1
- causes an internal state dump (the default dump file is
/var/run/xinetd.dump; to change the filename, edit config.h
and recompile).
- SIGABRT
- causes an internal consistency check to verify that the data structures
used by the program have not been corrupted. When the check is completed
xinetd will generate a message that says if the check was
successful or not.
On reconfiguration the log files are closed and reopened. This allows removal of
old log files.
FILES¶
- /etc/xinetd.conf
- default configuration file
- /var/run/xinetd.dump
- default dump file
SEE ALSO¶
inetd(8),
xinetd.conf(5),
xinetd.log(5)
http://cr.yp.to/daemontools.html
AUTHOR¶
Panos Tsirigotis, CS Dept, University of Colorado, Boulder Rob Braun
PRONUNCIATION¶
zy-net-d
