1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd April 12, 2025 29.Dt REBOOT 8 30.Os 31.Sh NAME 32.Nm reboot , 33.Nm halt , 34.Nm fastboot , 35.Nm fasthalt 36.Nd stopping and restarting the system 37.Sh SYNOPSIS 38.Nm halt 39.Op Fl DflNnpq 40.Op Fl e Ar variable=value 41.Op Fl k Ar kernel 42.Op Fl o Ar options 43.Nm 44.Op Fl cDdflNnpqr 45.Op Fl e Ar variable=value 46.Op Fl k Ar kernel 47.Op Fl o Ar options 48.Nm fasthalt 49.Op Fl DflNnpq 50.Op Fl e Ar variable=value 51.Op Fl k Ar kernel 52.Op Fl o Ar options 53.Nm fastboot 54.Op Fl dDflNnpq 55.Op Fl e Ar variable=value 56.Op Fl k Ar kernel 57.Op Fl o Ar options 58.Sh DESCRIPTION 59The 60.Nm halt 61and 62.Nm 63utilities flush the file system cache to disk, send all running processes 64a 65.Dv SIGTERM 66(and subsequently a 67.Dv SIGKILL ) 68and, respectively, halt or restart the system. 69The action is logged, including entering a shutdown record into the user 70accounting database. 71.Pp 72The options are as follows: 73.Bl -tag -width indent 74.It Fl c 75The system will turn off the power and then turn it back on if it can. 76If the power down action fails, the system 77will halt or reboot normally, depending on whether 78.Nm halt 79or 80.Nm 81was called. 82At the present time, only the 83.Xr ipmi 4 84driver implements the power cycle functionality and only on hardware 85with a BMC that supports power cycling. 86Unlike power off, the amount of hardware that supports power cycling 87is small. 88.It Fl D 89Delete existing 90.Nm nextboot 91configuration and exit. 92.It Fl d 93The system is requested to create a crash dump. 94This option is 95supported only when rebooting, and it has no effect unless a dump 96device has previously been specified with 97.Xr dumpon 8 . 98.It Fl e Ar variable=value 99Sets 100.Va variable 101to 102.Va value 103in the loader's and kernel's environment. 104If 105.Va value 106is not already enclosed in double quotes, they will be added before writing to the 107.Nm nextboot 108configuration. 109Care should be taken if 110.Va value 111contains any characters that are special to the shell or loader's configuration 112parsing code. 113.It Fl f 114Force reboot. 115Normally, 116.Nm 117checks for the presence of the next kernel, 118and absence of the 119.Pa /var/run/noshutdown 120file. 121Without this flag, reboot is denied if one of the conditions failed. 122.It Fl k Ar kname 123Boot the specified kernel 124.Ar kname 125on the next system boot. 126This is a one-shot option, the 127.Em default 128kernel will be booted on successive boots. 129No 130.Nm reboot 131or 132.Nm halt 133will be performed if 134.Em /boot/kname/kernel 135does not exist unless the 136.Fl f 137flag is specified. 138.It Fl l 139The halt or reboot is 140.Em not 141logged to the system log. 142This option is intended for applications such as 143.Xr shutdown 8 , 144that call 145.Nm 146or 147.Nm halt 148and log this themselves. 149.It Fl N 150The file system cache is not flushed during the initial process clean-up, 151however the kernel level 152.Xr reboot 2 153is still processed with a sync. 154This option can be useful for performing a 155.Dq best-effort 156reboot when devices might be unavailable. 157This can happen when devices have been disconnected, such as with 158.Xr iscsi 4 . 159.It Fl n 160The file system cache is not flushed. 161This option should probably not be used. 162.It Fl o Ar options 163This option 164allows the passing of kernel flags for the next boot. 165.It Fl p 166The system will turn off the power if it can. 167If the power down action fails, the system 168will halt or reboot normally, depending on whether 169.Nm halt 170or 171.Nm 172was called. 173.It Fl q 174The system is halted or restarted quickly and ungracefully, and only 175the flushing of the file system cache is performed (if the 176.Fl n 177option is not specified). 178This option should probably not be used. 179.It Fl r 180The system kills all processes, unmounts all filesystems, mounts the new 181root filesystem, and begins the usual startup sequence. 182After changing vfs.root.mountfrom with 183.Xr kenv 1 , 184.Nm Fl r 185can be used to change the root filesystem while preserving kernel state. 186This requires the 187.Xr tmpfs 4 188kernel module to be loaded because 189.Xr init 8 190needs a place to store itself after the old root is unmounted, but 191before the new root is in place. 192.El 193.Pp 194The 195.Nm fasthalt 196and 197.Nm fastboot 198utilities are nothing more than aliases for the 199.Nm halt 200and 201.Nm 202utilities. 203.Pp 204Normally, the 205.Xr shutdown 8 206utility is used when the system needs to be halted or restarted, giving 207users advance warning of their impending doom and cleanly terminating 208specific programs. 209.Sh EXAMPLES 210Replace current root filesystem with UFS mounted from 211.Pa /dev/ada0s1a : 212.Bd -literal -offset indent 213kenv vfs.root.mountfrom=ufs:/dev/ada0s1a 214reboot -r 215.Ed 216.Pp 217This mechanism can also be used with NFS, with a caveat that 218it only works with NFSv4, and requires a numeric IPv4 address: 219.Bd -literal -offset indent 220kenv vfs.root.mountfrom=nfs:192.168.1.1:/share/name 221reboot -r 222.Ed 223.Sh SEE ALSO 224.Xr kenv 1 , 225.Xr reboot 2 , 226.Xr getutxent 3 , 227.Xr ipmi 4 , 228.Xr boot 8 , 229.Xr dumpon 8 , 230.Xr nextboot 8 , 231.Xr savecore 8 , 232.Xr shutdown 8 , 233.Xr sync 8 234.Sh HISTORY 235A 236.Nm 237utility appeared in 238.Bx 4.0 . 239