.TH REBOOT 8
.CT 1 sa_auto
.SH NAME
reboot \- bootstrapping procedures
.SH DESCRIPTION
.PP
Here are some recipes for booting and crashing the operating system
on VAXes.
.SS Rebooting a running system
The preferred way to reboot is to log in on the console as super-user,
invoke
.B kill 1
to take the system to single user,
unmount file systems with
.B /etc/umount -a
and halt and restart the system
as described below under `Console boots.'
.SS Power fail and crash recovery
The system will reboot itself at power-up or after crashes if
auto-boot is enabled on the machine front panel
or in the console software.
If auto-restart is enabled,
the system will first attempt to save a copy of physical memory
on a reserved piece of disk.
An automatic consistency check of the file systems is performed.
Unless this fails the system will resume multi-user operations.
.SS Console boots
Sync the disks if necessary and possible.
To recover hardware control of the console, type a
.RB control- P .
This will yield a
.L >>>
prompt from the VAX
console subsystem (sic).
The command
.IP
.B >>> H
.LP
will halt the CPU
(except on the 11/750,
where
.RB control- P
halts the CPU right away).
.PP
On MicroVAXes,
.RB control- P
doesn't work;
hit the
.SM BREAK
key instead.
.PP
To boot multi-user with an automatic file system check,
give the console command
.IP
.B >>> B
.LP
Commands to boot single-user vary.
On the VAX-11/750 and on MicroVAXes,
use
.IP
.B >>> B/3
.LP
On the VAX-11/780 and VAX 8550 and 8700,
use
.IP
.B >>> B MAN
.LP
This will prompt with 
.LR *
for the name of the file to boot.
The filename should be an executable image
in the root directory
of the filesystem at the beginning of the disk.
.SS System core images
If the system crashes
and auto-restart is enabled,
a copy of physical memory is written
to a reserved piece of disk.
To save a core image of a hung system, type on the console (after
.RB control- P
if necessary):
.IP
.EX
>>> S 80000010
.EE
.PP
The system will write the core image,
then reboot automatically.
.PP
If the core image was written on
.LR /dev/ra11 ,
the following incantation will print a stack traceback
from the time of the crash:
.IP
.EX
adb /unix /dev/ra11
$<crash
$c
.EE
.PP
To save disk space,
the core image is sometimes overlaid on part of the swap area,
where normal system operation will soon overwrite it.
.IR Savecore (8)
will copy the core image
to an ordinary disk file.
.SH FILES
.TP
.F /unix
default system binary
.SH "SEE ALSO"
.IR fsck (8), 
.IR init (8), 
.IR rc (8),
.IR savecore (8)
.SH BUGS
Older boot programs with different syntax are still around in a few places,
especially on machines with Emulex UNIBUS disk controllers,
for which silly boot ROMs are common.
.PP
There are commands
.B /etc/reboot
and
.B /etc/halt
which attempt to reboot and halt the system;
their function is indeterminate
and likely to change.