REBOOT(8)REBOOT(8)NAME
reboot - UNIX bootstrapping procedures
SYNOPSIS
reboot [ -n ] [ -q ]
DESCRIPTION
UNIX is started by placing it in memory at location zero and transfer‐
ring to the entry point. Since the system is not reenterable, it is
necessary to read it in from disk or tape each time it is to be boot‐
strapped.
Rebooting a running system. When a UNIX is running and a reboot is
desired, shutdown(8) is normally used. If there are no users then
reboot can be used. Reboot causes the disks to be synced and allows
the system to perform other shutdown activities such as resynchronizing
hardware time-of-day clocks. A multi-user reboot (as described below)
is then initiated. This causes a system to be booted and an automatic
disk check to be performed. If all this succeeds without incident, the
system is then brought up for many users.
Options to reboot are:
-n option avoids the sync. It can be used if a disk or the proces‐
sor is on fire.
-q reboots quickly and ungracefully, without shutting down running
processes first.
Reboot normally logs the reboot using syslog(8) and places a shutdown
record in the login accounting file /var/log/wtmp. These actions are
inhibited if the -n or -q options are present.
Power fail and crash recovery. Normally, the system will reboot itself
at power-up or after crashes. An automatic consistency check of the
file systems will be performed as described in fsck(8). and unless
this fails, the system will resume multi-user operations.
Cold starts. These are processor-type dependent. On the CCI Power
6/32 and related processors, the system will do a standard autoboot
from drive 0 upon power-up or reset. This automatic boot may be can‐
celled by typing a “#” in the first few seconds after reset. This
enters console mode; the console prompt is “>” or “#>”. The boot flags
can be set to any hexadecimal value n with the command
#> p23 n.
The default device may be examined or set; see the Diagnostics and
Debugging manual for the processor for details on device naming and
syntax. After setting the boot flags and/or device, a bootstrap
sequence can be initiated with
#> fb
A specific device or bootstrap file may be used; for example,
#> fb xfd(1,0)
would boot from the `a' partition on XFD drive 1.
The file specifications used for the boostrap when loaded with the
“askme” flag (register 23 set to 1 or 3) are of the form:
device(adaptor,controller,unit,minor)
where device is the type of the device to be searched, adaptor is num‐
ber of the VERSAbus (or VMEbus) to which the device is attached, con‐
troller is the unit number of the controller on that buss, unit is the
unit number of the disk or tape, and minor is the disk partition or
tape file number. Leading adaptor or controller numbers default to 0.
Normal line editing characters can be used when typing the file speci‐
fication. The following list of supported devices may vary from
installation to installation:
dk SMD or ESDI disks on VDDC or SMD-E
cy tape on Ciprico Tapemaster controller
For example, to boot from a file system which starts at cylinder 0 of
unit 0 of an SMD-E disk, type “dk(0,0)vmunix” to the boot prompt;
“dk(2,1,0)vmunix” would specify drive 1 on SMD-E controller 2.
In an emergency, the bootstrap methods described in the paper
``Installing and Operating 4.3BSD-tahoe UNIX on the Tahoe'' can be used
to boot from a distribution tape.
FILES
/vmunix system code
/boot system bootstrap
SEE ALSOcrash(8), disklabel(8), fsck(8), halt(8), init(8), rc(8), shutdown(8),
syslogd(8)BUGS
The disklabel format used by some versions of the console processor is
different than the format used by UNIX and the bootstrap.
4th Berkeley Distribution June 24, 1990 REBOOT(8)
