1XINETD(8) System Manager's Manual XINETD(8)
2
6 xinetd - the extended Internet services daemon
7
9 xinetd [options]
10
12 xinetd performs the same function as inetd: it starts programs that
13 provide Internet services. Instead of having such servers started at
14 system initialization time, and be dormant until a connection request
15 arrives, xinetd is the only daemon process started and it listens on
16 all service ports for the services listed in its configuration file.
17 When a request comes in, xinetd starts the appropriate server. Because
18 of the way it operates, xinetd (as well as inetd) is also referred to
19 as a super-server.
20 The services listed in xinetd's configuration file can be separated
22 into two groups. Services in the first group are called multi-threaded
23 and they require the forking of a new server process for each new con‐
24 nection request. The new server then handles that connection. For
25 such services, xinetd keeps listening for new requests so that it can
26 spawn new servers. On the other hand, the second group includes ser‐
27 vices for which the service daemon is responsible for handling all new
28 connection requests. Such services are called single-threaded and
29 xinetd will stop handling new requests for them until the server dies.
30 Services in this group are usually datagram-based.
31 So far, the only reason for the existence of a super-server was to con‐
33 serve system resources by avoiding to fork a lot of processes which
34 might be dormant for most of their lifetime. While fulfilling this
35 function, xinetd takes advantage of the idea of a super-server to pro‐
36 vide features such as access control and logging. Furthermore, xinetd
37 is not limited to services listed in /etc/services. Therefore, anybody
38 can use xinetd to start special-purpose servers.
39 BEWARE of xinetd reload termination handling. For services with type =
41 INTERNAL, SIGTERM signal will be sent. For services without type =
42 INTERNAL, SIGKILL signall will be sent. Take this into an account when
43 dealing with proper handling of the SIGTERM and SIGKILL. It is impor‐
44 tant to be aware of this as your xinetd service could be killed on a
45 xinetd reload.
46
48 -d Enables debug mode. This produces a lot of debugging output, and
49 it makes it possible to use a debugger on xinetd.
50 -syslog syslog_facility
52 This option enables syslog logging of xinetd-produced messages
53 using the specified syslog facility. The following facility
54 names are supported: daemon, auth, user, local[0-7] (check sys‐
55 log.conf(5) for their meanings). This option is ineffective in
56 debug mode since all relevant messages are sent to the terminal.
57 -filelog logfile
59 xinetd-produced messages will be placed in the specified file.
60 Messages are always appended to the file. If the file does not
61 exist, it will be created. This option is ineffective in debug
62 mode since all relevant messages are sent to the terminal.
63 -f config_file
65 Determines the file that xinetd uses for configuration. The
66 default is /etc/xinetd.conf.
67 -pidfile pid_file
69 The process ID is written to the file. This option is ineffec‐
70 tive in debug mode.
71 -dontfork
73 Tells xinetd to stay in the foreground rather than detaching
74 itself, to support being run from init or daemontools. This
75 option automatically sets -stayalive (see below).
76 -stayalive
78 Tells xinetd to stay running even if no services are specified.
79 -limit proc_limit
81 This option places a limit on the number of concurrently running
82 processes that can be started by xinetd. Its purpose is to pre‐
83 vent process table overflows.
84 -logprocs limit
86 This option places a limit on the number of concurrently running
87 servers for remote userid acquisition.
88 -version
90 This option causes xinetd to print out its version information.
91 -inetd_compat
93 This option causes xinetd to read /etc/inetd.conf in addition to
94 the standard xinetd config files. /etc/inetd.conf is read after
95 the standard xinetd config files.
96 -cc interval
98 This option instructs xinetd to perform periodic consistency
99 checks on its internal state every interval seconds.
100 The syslog and filelog options are mutually exclusive. If none is
102 specified, the default is syslog using the daemon facility. You should
103 not confuse xinetd messages with messages related to service logging.
104 The latter are logged only if this is specified via the configuration
105 file.
106
108 xinetd performs certain actions when it receives certain signals. The
109 actions associated with the specific signals can be redefined by edit‐
110 ing config.h and recompiling.
111 SIGHUP causes a hard reconfiguration, which means that xinetd
113 re-reads the configuration file and terminates the
114 servers for services that are no longer available.
115 Access control is performed again on running servers by
116 checking the remote location, access times and server
117 instances. If the number of server instances is lowered,
118 some arbitrarily picked servers will be killed to sat‐
119 isfy the limit; this will happen after any servers are
120 terminated because of failing the remote location or
121 access time checks. Also, if the INTERCEPT flag was
122 clear and is set, any running servers for that service
123 will be terminated; the purpose of this is to ensure
124 that after a hard reconfiguration there will be no run‐
125 ning servers that can accept packets from addresses that
126 do not meet the access control criteria.
127 SIGQUIT causes program termination.
129 SIGTERM terminates all running servers before terminating
131 xinetd.
132 SIGUSR1 causes an internal state dump (the default dump file is
134 /var/run/xinetd.dump; to change the filename, edit con‐
135 fig.h and recompile).
136 SIGIOT causes an internal consistency check to verify that the
138 data structures used by the program have not been cor‐
139 rupted. When the check is completed xinetd will gener‐
140 ate a message that says if the check was successful or
141 not.
142 On reconfiguration the log files are closed and reopened. This allows
144 removal of old log files.
145
147 /etc/xinetd.conf default configuration file
148 /var/run/xinetd.dump
149 default dump file
150
152 inetd(8),
153 xinetd.conf(5),
155 xinetd.log(5)
157 http://cr.yp.to/daemontools.html
159
161 Panos Tsirigotis, CS Dept, University of Colorado, Boulder Rob Braun
162
164 zy-net-d
165 14 June 2001 XINETD(8)