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28 .\" @(#)reboot.2 8.1 (Berkeley) 6/4/93
36 .Nd reboot system or halt processor
43 .Fn reboot "int howto"
49 Only the super-user may reboot a machine on demand.
50 However, a reboot is invoked
51 automatically in the event of unrecoverable system failures.
56 is a mask of options; the system call interface allows the following
57 options, defined in the include file
60 to the new kernel or the new bootstrap and init programs.
61 .Bl -tag -width RB_POWERCYCLE
63 The default, causing the system to reboot in its usual fashion.
65 Normally the system only prompts the user if the loader specified root
66 file system has an error.
67 This flag forces it to always prompt the user for the root partition.
69 Use the compiled in root device.
70 Normally, the system uses the device from which it was booted
71 as the root device if possible.
72 (The default behavior is dependent on the ability of the bootstrap program
73 to determine the drive from which it was loaded, which is not possible
76 Dump kernel memory before rebooting; see
80 The processor is simply halted; no reboot takes place.
81 This option should be used with caution.
83 After halting, the shutdown code will do what it can to turn
84 off the power and then turn the power back on.
85 This requires hardware support, usually an auxiliary microprocessor
86 that can sequence the power supply.
89 driver implements this feature.
91 After halting, the shutdown code will do what it can to turn
93 This requires hardware support.
95 Load the symbol table and enable a built-in debugger in the system.
96 This option will have no useful function if the kernel is not configured
98 Several other options have different meaning if combined
99 with this option, although their use may not be possible
105 for more information.
107 Normally, the disks are sync'd (see
109 before the processor is halted or rebooted.
110 This option may be useful if file system changes have been made manually
111 or if the processor is on fire.
113 Instead of rebooting, unmount all filesystems except the one containing
114 currently-running executable, and mount root filesystem using the same
115 mechanism which is used during normal boot, based on
120 Initially mount the root file system read-only.
121 This is currently the default, and this option has been deprecated.
123 Normally, the reboot procedure involves an automatic disk consistency
124 check and then multi-user operations.
126 prevents this, booting the system with a single-user shell
129 is actually interpreted by the
131 program in the newly booted system.
134 When no options are given (i.e.,
136 is used), the system is
139 in the root file system of unit 0
140 of a disk chosen in a processor specific way.
141 An automatic consistency check of the disks is normally performed
145 If successful, this call never returns.
146 Otherwise, a -1 is returned and an error is returned in the global
152 The caller is not the super-user.
163 system call appeared in