XINETD - phpMan

XINETD(8) XINETD(8)

NAME
xinetd - the extended Internet services daemon

SYNOPSIS
xinetd [options]

DESCRIPTION
xinetd performs the same function as inetd: it starts programs that provide Inter-
net 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. Further-
more, xinetd is not limited to services listed in /etc/services. Therefore, any-
body 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: dae-
mon, 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 cre-
ated. 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 sup-
port 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 stan-
dard 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 mes-
sages 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 arbi-
trarily 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).

SIGIOT causes an internal consistency check to verify that the data struc-
tures 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