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halt(8) [debian man page]

HALT(8) 						Linux System Administrator's Manual						   HALT(8)

halt, reboot, poweroff - stop the system. SYNOPSIS
/sbin/halt [-n] [-w] [-d] [-f] [-i] [-p] [-h] /sbin/reboot [-n] [-w] [-d] [-f] [-i] /sbin/poweroff [-n] [-w] [-d] [-f] [-i] [-h] DESCRIPTION
halt notes that the system is being brought down in the file /var/log/wtmp, and then either tells the kernel to halt, reboot or power-off the system. If halt or reboot is called when the system is not in runlevel 0 or 6, in other words when it's running normally, shutdown will be invoked instead (with the -h or -r flag). For more info see the shutdown(8) manpage. The rest of this manpage describes the behaviour in runlevels 0 and 6, that is when the systems shutdown scripts are being run. OPTIONS
-n Don't sync before reboot or halt. Note that the kernel and storage drivers may still sync. This implies -d. -w Don't actually reboot or halt but only write the wtmp record (in the /var/log/wtmp file). -d Don't write the wtmp record. -f Force halt or reboot, don't call shutdown(8). -i Shut down all network interfaces just before halt or reboot. -h Put all hard drives on the system in stand-by mode just before halt or power-off. -p When halting the system, switch off the power. This is the default when halt is called as poweroff. DIAGNOSTICS
If you're not the superuser, you will get the message `must be superuser'. NOTES
Under older sysvinit releases , reboot and halt should never be called directly. From release 2.74 on halt and reboot invoke shutdown(8) if the system is not in runlevel 0 or 6. This means that if halt or reboot cannot find out the current runlevel (for example, when /var/run/utmp hasn't been initialized correctly) shutdown will be called, which might not be what you want. Use the -f flag if you want to do a hard halt or reboot. The -h flag puts all hard disks in standby mode just before halt or power-off. Right now this is only implemented for IDE drives. A side effect of putting the drive in stand-by mode is that the write cache on the disk is flushed. This is important for IDE drives, since the kernel doesn't flush the write cache itself before power-off. The halt program uses /proc/ide/hd* to find all IDE disk devices, which means that /proc needs to be mounted when halt or poweroff is called or the -h switch will do nothing. AUTHOR
Miquel van Smoorenburg, SEE ALSO
shutdown(8), init(8) Nov 6, 2001 HALT(8)

Check Out this Related Man Page

reboot(8)						      System Manager's Manual							 reboot(8)

reboot, halt, poweroff - reboot or stop the system SYNOPSIS
reboot [OPTION]... halt [OPTION]... poweroff [OPTION]... DESCRIPTION
These programs allow a system administrator to reboot, halt or poweroff the system. When called with --force or when in runlevel 0 or 6, this tool invokes the reboot(2) system call itself and directly reboots the system. Otherwise this simply invokes the shutdown(8) tool with the appropriate arguments. Before invoking reboot(2), a shutdown time record is first written to /var/log/wtmp OPTIONS
-f, --force Does not invoke shutdown(8) and instead performs the actual action you would expect from the name. -p, --poweroff Instructs the halt command to instead behave as poweroff. -w, --wtmp-only Does not call shutdown(8) or the reboot(2) system call and instead only writes the shutdown record to /var/log/wtmp --verbose Outputs slightly more verbose messages when rebooting, useful for debugging problems with shutdown. ENVIRONMENT
RUNLEVEL reboot will read the current runlevel from this environment variable if set in preference to reading from /var/run/utmp FILES
/var/run/utmp Where the current runlevel will be read from; this file will also be updated with the runlevel record being replaced by a shutdown time record. /var/log/wtmp A new runlevel record for the shutdown time will be appended to this file. AUTHOR
Written by Scott James Remnant <> REPORTING BUGS
Report bugs at <> COPYRIGHT
Copyright (C) 2009 Canonical Ltd. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU- LAR PURPOSE. SEE ALSO
shutdown(8) telinit(8) runlevel(8) Upstart 2009-07-09 reboot(8)
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