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 December 8, 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 stop and restart the system, respectively. 64.Pp 65Both utilities have two distinct modes of operation. 66In normal mode, they send a signal to the 67.Xr init 8 68process, which shuts down running services and stops or restarts the 69system. 70In fast mode, they flush the file system cache to disk, send all 71running processes a 72.Dv SIGTERM 73(and subsequently a 74.Dv SIGKILL ) 75and stop or restart the system themselves. 76Services are killed, not shut down, which may result in data loss. 77.Pp 78In either mode, the action is logged, including entering a shutdown 79record into the user accounting database. 80.Pp 81The following options are available: 82.Bl -tag -width indent 83.It Fl c 84The system will turn off the power and then turn it back on if it can. 85If the power down action fails, the system 86will halt or reboot normally, depending on whether 87.Nm halt 88or 89.Nm 90was called. 91At the present time, only the 92.Xr ipmi 4 93driver implements the power cycle functionality and only on hardware 94with a BMC that supports power cycling. 95Unlike power off, the amount of hardware that supports power cycling 96is small. 97.It Fl D 98Delete existing 99.Nm nextboot 100configuration and exit. 101.It Fl d 102The system is requested to create a crash dump. 103This option is 104supported only when rebooting, and it has no effect unless a dump 105device has previously been specified with 106.Xr dumpon 8 . 107.It Fl e Ar variable=value 108Sets 109.Va variable 110to 111.Va value 112in the loader's and kernel's environment. 113If 114.Va value 115is not already enclosed in double quotes, they will be added before writing to the 116.Nm nextboot 117configuration. 118Care should be taken if 119.Va value 120contains any characters that are special to the shell or loader's configuration 121parsing code. 122.It Fl f 123Forced mode. 124Normally, 125.Nm halt 126or 127.Nm 128checks for the presence of the next kernel, 129and absence of the 130.Pa /var/run/noshutdown 131file. 132Without this flag, the operation is rejected if one of these checks 133fails. 134.It Fl k Ar kname 135Boot the specified kernel 136.Ar kname 137on the next system boot. 138This is a one-shot option, the 139.Em default 140kernel will be booted on successive boots. 141No 142.Nm reboot 143or 144.Nm halt 145will be performed if 146.Em /boot/kname/kernel 147does not exist unless the 148.Fl f 149flag is specified. 150.It Fl l 151The halt or reboot is 152.Em not 153logged to the system log. 154This option is intended for applications such as 155.Xr shutdown 8 , 156that call 157.Nm 158or 159.Nm halt 160and log this themselves. 161.It Fl N 162The file system cache is not flushed during the initial process clean-up, 163however the kernel level 164.Xr reboot 2 165is still processed with a sync. 166This option can be useful for performing a 167.Dq best-effort 168reboot when devices might be unavailable. 169This can happen when devices have been disconnected, such as with 170.Xr iscsi 4 . 171.It Fl n 172The file system cache is not flushed. 173This option should probably not be used. 174.It Fl o Ar options 175This option 176allows the passing of kernel flags for the next boot. 177.It Fl p 178The system will turn off the power if it can. 179If the power down action fails, the system 180will halt or reboot normally, depending on whether 181.Nm halt 182or 183.Nm 184was called. 185.It Fl q 186The system is halted or restarted quickly and ungracefully, and only 187the flushing of the file system cache is performed (if the 188.Fl n 189option is not specified). 190This option should probably not be used. 191.It Fl r 192The system kills all processes, unmounts all filesystems, mounts the new 193root filesystem, and begins the usual startup sequence. 194After changing vfs.root.mountfrom with 195.Xr kenv 1 , 196.Nm Fl r 197can be used to change the root filesystem while preserving kernel state. 198This requires the 199.Xr tmpfs 4 200kernel module to be loaded because 201.Xr init 8 202needs a place to store itself after the old root is unmounted, but 203before the new root is in place. 204.El 205.Pp 206The 207.Nm fasthalt 208and 209.Nm fastboot 210utilities invoke 211.Nm halt 212and 213.Nm , 214respectively, in fast mode. 215.Pp 216The 217.Xr shutdown 8 218utility can be used to not only stop or restart the system right away, 219but also schedule a stop or restart in the future, and will, unlike 220.Nm halt 221and 222.Nm , 223give users advance warning of their impending doom. 224.Sh EXAMPLES 225Replace current root filesystem with UFS mounted from 226.Pa /dev/ada0s1a : 227.Bd -literal -offset indent 228kenv vfs.root.mountfrom=ufs:/dev/ada0s1a 229reboot -r 230.Ed 231.Pp 232This mechanism can also be used with NFS, with a caveat that 233it only works with NFSv4, and requires a numeric IPv4 address: 234.Bd -literal -offset indent 235kenv vfs.root.mountfrom=nfs:192.168.1.1:/share/name 236reboot -r 237.Ed 238.Sh SEE ALSO 239.Xr kenv 1 , 240.Xr reboot 2 , 241.Xr getutxent 3 , 242.Xr ipmi 4 , 243.Xr boot 8 , 244.Xr dumpon 8 , 245.Xr nextboot 8 , 246.Xr savecore 8 , 247.Xr shutdown 8 , 248.Xr sync 8 249.Sh HISTORY 250A 251.Nm 252utility appeared in 253.Bx 4.0 . 254.Pp 255Historically, the 256.Xr shutdown 8 257utility was used when the system needed to be halted or restarted 258cleanly in the normal course of operations, and the 259.Nm halt 260and 261.Nm 262utilities were blunt instruments used only in single-user mode or if 263exceptional circumstances made a normal shutdown impractical. 264As other operating systems did away with this distinction, and it 265became clear that many users were unaware of it and were using 266.Nm 267in the belief that it performed a clean shutdown, it was rewritten to 268conform to that expectation. 269