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1 perry 1 callback
2 !!!callback
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 OPTIONS
7 CONFIG FILE
8 DIAGNOSTICS
9 INTERNALS
10 BUGS
11 SEE ALSO
12 AUTHOR
13 ----
14 !!NAME
15
16
17 callback - call a user back, presenting a login prompt
18 !!SYNOPSIS
19
20
21 __callback__ [[__-x____level__]
22 [[__-V__] [[__-l____lines__]
23 [[__-m____]__
24 [[__-s____]__ [[__-d__] [[__-S__]
25 [[''phone-number'']
26 !!DESCRIPTION
27
28
29 Call the given phone number (if none is given on the command
30 line, ask user for one), and if a CONNECT is established,
31 hand over control to mgetty(8) to present user with a login
32 name prompt.
33
34
35 ''callback'' is used for various purposes:
36
37
38 * security: make sure your users are who they pretend to be
39 by calling a well-known phone number.
40
41
42 * cost savings: make your company call you
43 back.
44
45
46 ''callback'' can be called directly from the command line
47 (but you must be
48 ''
49 !!OPTIONS
50
51
52 __-x __
53
54
55 Use the given level of verbosity for logging - 0 means no
56 logging, 5 is really noisy.
57
58
59 __-V__
60
61
62 Print version number and quit.
63
64
65 __-d__
66
67
68 Do not go into the background. This is helpful for
69 debugging.
70
71
72 __-l __
73
74
75 Use the given modem lines. Multiple lines can be separated
76 by
77
78
79 __-m __
80
81
82 Set the modem initialization sequence (as usual: expect send
83 expect ...). This can do nearly everything, as long as it
84 leaves the modem command responses on (that is, no ATQ1
85 here!) and switches the modem to data mode (AT+FCLASS=0) if
86 it is used in data/fax mode.
87
88
89 __-s __
90
91
92 This is the bit rate that should be used for the
93 machine-modem connection. Usually you'll set this via the
94
95
96 __-S__
97
98
99 Use the line where callback is started from for dialing out.
100 Callback can make use of multiple modem lines, and with this
101 options, you can force it to use just one modem, the one
102 where a call comes in.
103 !!CONFIG FILE
104
105
106 ''callback'' will read all its configuration at run-time
107 from a file, usually called /etc/mgetty/callback.config. See
108 the documentation in the mgetty.info manual for
109 details.
110 !!DIAGNOSTICS
111
112
113 In most cases, ''callback'' can't print any error
114 messages to the console, because it must detach itself
115 immediately from the terminal, in case someone wants to be
116 called back on the modem line he called in. So, nothing to
117 print messages to...
118
119
120 Because of this, all callback errors are logged to a
121 protocol file (the extent of the data written is controlled
122 by the
123
124
125 Just two messages are printed on stdout, and those are
126 self-explaining, a call from a non-root user, and an invalid
127 option.
128 !!INTERNALS
129
130
131 How does it work?
132
133
134 This is a bit tricky, because of the way init(8) handles the
135 utmp(5) file. You can't just have any program ask the user
136 for a login name, and then start a
137 mgetty(8)''
138 has to be started from /etc/inittab).
139
140
141 So, mgetty has to do the
142
143
144 The way it works is this: ''callback'' dials out on a
145 modem device. It will only take a modem device that has a
146 mgetty watching over it (!). When the connection is
147 established (CONNECT), ''callback'' will send a signal
148 SIGUSR1 to mgetty, which, in turn, will send the same signal
149 back to signal
150 ''callback'' then exits, and ''mgetty'' takes over the
151 existing connection, prompts the user for a login name, and
152 forks off /bin/login.
153
154
155 Conclusion: this will not work with mgetty versions before
156 February 04, 1996 (no support for this signalling), and if
157 it doesn't work for you, please send me __BOTH__ the
158 mgetty and the callback log file, otherwise it's very hard
159 to find the bugs.
160 !!BUGS
161
162
163 ''callback'' is
164 ''
165
166
167 ''callback'' is fairly dumb concerning
168 retries.
169
170
171 ''callback'' must be run as root.
172
173
174 Most of the documentation consists of
175 !!SEE ALSO
176
177
178 mgetty(8), ct(1)
179 !!AUTHOR
180
181
182 ''callback'' is Copyright (C) 1993-1996 by Gert Doering,
183 ''
184 ----
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