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1 .\" $OpenBSD: reboot.2,v 1.2 1996/10/08 01:20:13 michaels Exp $
2 .\" $NetBSD: reboot.2,v 1.5 1995/02/27 12:36:02 cgd Exp $
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35 .\" @(#)reboot.2 8.1 (Berkeley) 6/4/93
36 .\"
37 .Dd June 4, 1993
38 .Dt REBOOT 2
39 .Os BSD 4
40 .Sh NAME
41 .Nm reboot
42 .Nd reboot system or halt processor
43 .Sh SYNOPSIS
44 .Fd #include <unistd.h>
45 .Fd #include <sys/reboot.h>
46 .Ft int
47 .Fn reboot "int howto"
48 .Sh DESCRIPTION
49 .Fn Reboot
50 reboots the system. Only the super-user may reboot a machine on demand.
51 However, a reboot may be invoked automatically in the event of
52 unrecoverable system failures. Programs other than
53 .Xr reboot 8
54 should not call
55 .Fn reboot .
56 .Xr Shutdown 8
57 or a higher-level API will shut the system down cleanly.
58 .Pp
59 .Fa Howto
60 is a mask of options; the system call interface allows the following
61 options, defined in the include file
62 .Aq Pa sys/reboot.h ,
63 to be passed
64 to the new kernel or the new bootstrap and init programs.
65 .Bl -tag -width RB_INITNAMEA
66 .It Dv RB_AUTOBOOT
67 The default, causing the system to reboot in its usual fashion.
68 .It Dv RB_ASKNAME
69 Interpreted by the bootstrap program itself, causing it to
70 prompt on the console as to what file should be booted.
71 Normally, the system is booted from the file
72 .Dq Em xx Ns No (0,0)bsd ,
73 where
74 .Em xx
75 is the default disk name,
76 without prompting for the file name.
77 .It Dv RB_DFLTROOT
78 Use the compiled in root device.
79 Normally, the system uses the device from which it was booted
80 as the root device if possible.
81 (The default behavior is dependent on the ability of the bootstrap program
82 to determine the drive from which it was loaded, which is not possible
83 on all systems.)
84 .It Dv RB_DUMP
85 Dump kernel memory before rebooting; see
86 .Xr savecore 8
87 for more information.
88 .It Dv RB_HALT
89 the processor is simply halted; no reboot takes place.
90 This option should be used with caution.
91 .It Dv RB_INITNAME
92 An option allowing the specification of an init program (see
93 .Xr launchd 8 )
94 other than
95 .Pa /sbin/launchd
96 to be run when the system reboots.
97 This switch is not currently available.
98 .It Dv RB_KDB
99 Load the symbol table and enable a built-in debugger in the system.
100 This option will have no useful function if the kernel is not configured
101 for debugging.
102 Several other options have different meaning if combined
103 with this option, although their use may not be possible
104 via the
105 .Fn reboot
106 call.
107 See
108 .Xr kadb 4
109 for more information.
110 .It Dv RB_NOSYNC
111 Normally, the disks are sync'd (see
112 .Xr sync 8 )
113 before the processor is halted or rebooted.
114 This option may be useful if file system changes have been made manually
115 or if the processor is on fire.
116 .It Dv RB_RDONLY
117 Initially mount the root file system read-only.
118 This is currently the default, and this option has been deprecated.
119 .It Dv RB_SINGLE
120 Normally, the reboot procedure involves an automatic disk consistency
121 check and then multi-user operations.
122 .Dv RB_SINGLE
123 prevents this, booting the system with a single-user shell
124 on the console.
125 .Dv RB_SINGLE
126 is actually interpreted by the
127 .Xr launchd 8
128 program in the newly booted system.
129 .Pp
130 When no options are given (i.e.,
131 .Dv RB_AUTOBOOT
132 is used), the system is
133 rebooted from file ``bsd'' in the root file system of unit 0
134 of a disk chosen in a processor specific way.
135 An automatic consistency check of the disks is normally performed
136 (see
137 .Xr fsck 8 ) .
138 .El
139 .Sh RETURN VALUES
140 If successful, this call never returns.
141 Otherwise, a -1 is returned and an error is returned in the global
142 variable
143 .Va errno .
144 .Sh ERRORS
145 .Bl -tag -width Er
146 .It Bq Er EPERM
147 The caller is not the super-user.
148 .El
149 .Sh SEE ALSO
150 .Xr shutdown 8 ,
151 .Xr halt 8 ,
152 .Xr launchd 8 ,
153 .Xr reboot 8
154 .Sh BUGS
155 The HP300 implementation supports neither
156 .Dv RB_DFLTROOT
157 nor
158 .Dv RB_KDB .
159 .Sh HISTORY
160 The
161 .Fn reboot
162 function call appeared in
163 .Bx 4.0 .