1.\" Copyright (c) 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software written and contributed 5.\" to Berkeley by William Jolitz. 6.\" 7.\" %sccs.include.redist.roff% 8.\" 9.\" @(#)boot_i386.8 1.2 (Berkeley) 04/25/91 10.\" 11.Dd 12.Dt REBOOT 8 13.Os 14.Sh NAME 15.Nm reboot 16.Nd 17.Tn UNIX 18bootstrapping procedures 19.Sh SYNOPSIS 20.Nm reboot 21.Op Fl n 22.Op Fl q 23.Sh DESCRIPTION 24.Tn UNIX , 25an ordinary executable file, 26is placed into memory by bootstrap at location absolute zero, and 27entered at the executable's entry point 28.Pq Va a_entry . 29Upon startup, the system reorganizes memory to suit the needs of 30the hardware configuration found, thus it is not designed to 31be restartable without being reloaded on reboot. 32Each time it is to be bootstrapped, it must be reloaded, usually from 33a disk file. 34.Pp 35.Sy Rebooting a running system . 36When a 37.Tn UNIX 38is running and a reboot is desired, 39.Xr shutdown 8 40is normally used. 41If there are no users then 42.Nm reboot 43can be used. 44Reboot causes the disks to be synced and allows the system 45to perform other shutdown activities such as resynchronizing 46hardware time-of-day clocks. 47A multi-user reboot (as described below) is then initiated. 48This causes a system to be 49booted and an automatic disk check to be performed. If all this succeeds 50without incident, the system is then brought up for many users. 51.Pp 52Options to reboot are: 53.Bl -tag -width indent 54.It Fl n 55option avoids the sync. It can be used if a disk or the processor 56is on fire. 57.It Fl q 58reboots quickly and ungracefully, without shutting down running 59processes first. 60.El 61.Pp 62.Nm Reboot 63normally logs the reboot using 64.Xr syslog 8 65and places a shutdown record in the login accounting file 66.Pa /var/log/wtmp . 67These actions are inhibited if the 68.Fl n 69or 70.Fl q 71options are present. 72.Pp 73.Sy Power fail and crash recovery. 74Normally, the system will reboot itself at power-up or after crashes. 75An automatic consistency check of the file systems will be performed 76as described in 77.Xr fsck 8 . 78and unless this fails, the system will resume multi-user operations. 79.Pp 80.Sy Cold starts . 81The 386 82.Tn "PC AT" 83clones attempt to boot the floppy disk drive A (otherwise 84known as drive 0) first, and failing that, attempt to boot the hard disk 85C (otherwise known as hard disk controller 1, drive 0). 86The automatic boot will attempt to load 87.Pa vmunix 88from partition A of 89either the floppy or the hard disk. This boot may be aborted by typing 90any character on the keyboard repeatedly (four or five times at least) 91during the operating system load phase, after which the bootstrap will 92prompt for the file that you wish to load instead. 93.Pp 94One exception to this is the 95.Ql d 96key, which will not abort the load but 97instead silently force the 98.Dv DEBUG 99boot flags. The boot flags for an autoboot 100are 0, and 3 for the successive boot after an aborted autoboot sequence. 101No other provison is made for setting boot flags (yet). 102A specific device or bootstrap file may be used; for example, 103.Pp 104The file specifications used for the boostrap 105when loaded with the 106.Dq askme 107flag 108(e.g. an aborted autoboot) 109are of the form: 110.Pp 111.Dl device unit partition: 112.Pp 113where 114.Ar device 115is the type of the device, assumed to be on the ISA bus, to be searched, 116.Ar unit 117is the unit number of the disk or tape, 118and 119.Ar partition 120is the disk partition or tape file number. 121Normal line editing characters can be used when typing the file specification. 122The following list of supported devices may vary from installation to 123installation: 124.Bd -unfilled -offset indent 125wd ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 126 controller 127fd 5 1/4" or 3 1/2" High density floppies 128.Ed 129.Pp 130For example, 131to boot from a file system which starts at cylinder 0 132of unit 0 of an IDE disk, type 133.Dq Li wd0a:vmunix 134to the boot prompt; 135.Dq Li fd0a:vmunix 136would specify a 3 1/2" floppy drive 0 . 137.Pp 138In an emergency, the bootstrap methods described in the paper 139.%T "Installing and Operating 4.3 BSD-Reno UNIX on the AT/386" 140can be used 141to boot from a distribution tape. 142.Sh FILES 143.Bl -tag -width /vmunixxx -compact 144.It Pa /vmunix 145system code 146.It Pa /boot 147system bootstrap 148.El 149.Sh SEE ALSO 150.Xr crash 8 , 151.Xr disklabel 8 , 152.Xr fsck 8 , 153.Xr halt 8 , 154.Xr init 8 , 155.Xr rc 8 , 156.Xr shutdown 8 , 157.Xr syslogd 8 158.Sh BUGS 159The disklabel format used by this version of 160.Bx 161is quite 162different from that of other architectures. 163