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1 perry 1 SHUTDOWN
2 !!!SHUTDOWN
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 ACCESS CONTROL
8 FILES
9 NOTES
10 AUTHOR
11 SEE ALSO
12 ----
13 !!NAME
14
15
16 shutdown - bring the system down
17 !!SYNOPSIS
18
19
20 __/sbin/shutdown__ [[__-t__ ''sec'']
21 [[__-arkhncfF__] ''time''
22 [[''warning-message'']
23 !!DESCRIPTION
24
25
26 __shutdown__ brings the system down in a secure way. All
27 logged-in users are notified that the system is going down,
28 and login(1) is blocked. It is possible to shut the
29 system down immediately or after a specified delay. All
30 processes are first notified that the system is going down
31 by the signal SIGTERM . This gives programs
32 like vi(1) the time to save the file being edited,
33 mail and news processing programs a chance to exit cleanly,
34 etc. __shutdown__ does its job by signalling the
35 __init__ process, asking it to change the runlevel.
36 Runlevel __0__ is used to halt the system, runlevel
37 __6__ is used to reboot the system, and runlevel __1__
38 is used to put to system into a state where administrative
39 tasks can be performed; this is the default if neither the
40 ''-h'' or ''-r'' flag is given to __shutdown__. To
41 see which actions are taken on halt or reboot see the
42 appropriate entries for these runlevels in the file
43 ''/etc/inittab''.
44 !!OPTIONS
45
46
47 __-a__
48
49
50 Use __/etc/shutdown.allow__.
51
52
53 __-t__ ''sec''
54
55
56 Tell init(8) to wait ''sec'' seconds between
57 sending processes the warning and the kill signal, before
58 changing to another runlevel.
59
60
61 __-k__
62
63
64 Don't really shutdown; only send the warning messages to
65 everybody.
66
67
68 __-r__
69
70
71 Reboot after shutdown.
72
73
74 __-h__
75
76
77 Halt after shutdown.
78
79
80 __-n__
81
82
83 [[DEPRECATED] Don't call init(8) to do the shutdown
84 but do it ourself. The use of this option is discouraged,
85 and its results are not always what you'd
86 expect.
87
88
89 __-f__
90
91
92 Skip fsck on reboot.
93
94
95 __-F__
96
97
98 Force fsck on reboot.
99
100
101 __-c__
102
103
104 Cancel an already running shutdown. With this option it is
105 of course not possible to give the __time__ argument, but
106 you can enter a explanatory message on the command line that
107 will be sent to all users.
108
109
110 ''time''
111
112
113 When to shutdown.
114
115
116 ''warning-message''
117
118
119 Message to send to all users.
120
121
122 The ''time'' argument can have different formats. First,
123 it can be an absolute time in the format ''hh:mm'', in
124 which ''hh'' is the hour (1 or 2 digits) and ''mm'' is
125 the minute of the hour (in two digits). Second, it can be in
126 the format __+__''m'', in which ''m'' is the number
127 of minutes to wait. The word __now__ is an alias for
128 __+0__.
129
130
131 If shutdown is called with a delay, it creates the advisory
132 file ''/etc/nologin'' which causes programs such as
133 ''login(1)'' to not allow new user logins. Shutdown
134 removes this file if it is stopped before it can signal init
135 (i.e. it is cancelled or something goes wrong). It also
136 removes it before calling init to change the
137 runlevel.
138
139
140 The __-f__ flag means `reboot fast'. This only creates an
141 advisory file ''/fastboot'' which can be tested by the
142 system when it comes up again. The boot rc file can test if
143 this file is present, and decide not to run fsck(1)
144 since the system has been shut down in the proper way. After
145 that, the boot process should remove
146 ''/fastboot''.
147
148
149 The __-F__ flag means `force fsck'. This only creates an
150 advisory file ''/forcefsck'' which can be tested by the
151 system when it comes up again. The boot rc file can test if
152 this file is present, and decide to run fsck(1) with
153 a special `force' flag so that even properly unmounted
154 filesystems get checked. After that, the boot process should
155 remove ''/forcefsck''.
156
157
158 The __-n__ flag causes __shutdown__ not to call
159 __init__, but to kill all running processes itself.
160 __shutdown__ will then turn off quota, accounting, and
161 swapping and unmount all filesystems.
162 !!ACCESS CONTROL
163
164
165 __shutdown__ can be called from init(8) when the
166 magic keys __CTRL-ALT-DEL__ are pressed, by creating an
167 appropriate entry in ''/etc/inittab''. This means that
168 everyone who has physical access to the console keyboard can
169 shut the system down. To prevent this, __shutdown__ can
170 check to see if an authorized user is logged in on one of
171 the virtual consoles. If __shutdown__ is called with the
172 __-a__ argument (add this to the invocation of shutdown
173 in /etc/inittab), it checks to see if the file
174 ''/etc/shutdown.allow'' is present. It then compares the
175 login names in that file with the list of people that are
176 logged in on a virtual console (from ''/var/run/utmp'').
177 Only if one of those authorized users __or root__ is
178 logged in, it will proceed. Otherwise it will write the
179 message
180
181
182 __shutdown: no authorized users logged in
183 __to the (physical) system console. The format of ''/etc/shutdown.allow'' is one user name per line. Empty lines and comment lines (prefixed by a __#__) are allowed. Currently there is a limit of 32 users in this file.
184
185
186 Note that if ''/etc/shutdown.allow'' is not present, the
187 __-a__ argument is ignored.
188 !!FILES
189
190
191 /fastboot
192 /etc/inittab
193 /etc/init.d/halt
194 /etc/init.d/reboot
195 /etc/shutdown.allow
196 !!NOTES
197
198
199 A lot of users forget to give the ''time'' argument and
200 are then puzzled by the error message __shutdown__
201 produces. The ''time'' argument is mandatory; in 90
202 percent of all cases this argument will be the word
203 __now__.
204
205
206 Init can only capture CTRL-ALT-DEL and start shutdown in
207 console mode. If the system is running the X window System,
208 the X server processes all key strokes. Some X11
209 environments make it possible to capture CTRL-ALT-DEL, but
210 what exactly is done with that event depends on that
211 environment.
212
213
214 Shutdown wasn't designed to be run setuid.
215 /etc/shutdown.allow is not used to find out who is executing
216 shutdown, it ONLY checks who is currently logged in on (one
217 of the) console(s).
218 !!AUTHOR
219
220
221 Miquel van Smoorenburg, miquels@cistron.nl
222 !!SEE ALSO
223
224
225 fsck(8), init(8), halt(8),
226 poweroff(8), reboot(8)
227 ----
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