term% cat index.txt REBOOT(8) System Manager's Manual REBOOT(8)
NAME
reboot - bootstrapping procedures
SYNOPSIS
/etc/reboot [ -s ] [ -n ] [ -a ] [ -d ]
/etc/halt [ -n ]
DESCRIPTION
UNIX is started by placing it in memory at location zero and transfer‐
ring to zero. Since the system is not reenterable, it is necessary to
read it in from disk each time it is to be bootstrapped.
Rebooting a running system
The preferred way to reboot is to log in on the console, invoke kill 1
to take the system to single user, unmount filesystems with /etc/umount
-a and halt and restart the system as described below under Console
boots.
If access to the console is difficult, /etc/reboot may be used to
restart a running system. It normally syncs the disks (see sync(8)),
then causes a system boot and an automatic disk check. If all this
succeeds, the system is brought up multi-user.
The options to reboot are:
-s Come up single-user after the reboot, without checking the
disks.
-n Don't sync the disks before performing the reboot.
-a Ask on the console for the name of the file to be booted.
-d Write a crash dump to the swap area before rebooting.
/etc/halt syncs the disks and stops the CPU. If the -n option is en‐
abled, the disk sync is not performed.
Power fail and crash recovery
The system will normally reboot itself at power-up or after crashes if
the auto-restart is enabled on the machine front panel. An automatic
consistency check of the file systems is performed. Unless this fails
the system will resume multi-user operations.
Console boots: VAX-11/750
Sync the disks if necessary and possible. To recover control of the
console (normally it is running as an ordinary Unix terminal), type a
control-P. This will halt the CPU and yield a `>>>' prompt from the
VAX console subsystem (sic). (Under undocumented conditions, this may
fail. If so, hit the white button on the front panel.) The command
>>> B
will cause a normal automatic reboot. Use
>>> B/3
to come up single-user. This also will prompt (with `:') for the name
of the file to boot. The format of the file name is
disk(m, n)file
where disk is `ra' for UDA50 disks with 4KB filesystems, `sa' for UDA50
disks with 1KB filesystems, `up' for UNIBUS SMD disks, `hp' for Massbus
SMD disks; m is the drive number (usually 0); n is the file system num‐
ber on the drive (usually 0); and file is the Unix name of the file on
the disk.
If the root disk is curdled, the bootstrap program /boot can be read
from another disk, say RA drive 1, by
>>> B/3 DUA1
To the console subsystem, the RA's are called DU; the Emulex disks are
EM. Note that regardless how a system is bootstrapped, it will use
drive 0 for the root disk.
Console boots: VAX-11/780
To halt a 780, type control-P, then issue the command
>>> H
to halt the CPU.
Rebooting a 780 is like a 750 except for the format of the B command.
>>> B
initiates automatic reboot.
>>> B ANY
comes up single user. Replace `ANY' by `HPS' for hp disk single user
reboot, `RPS' for rp reboot, and `UPS' for ra reboot.
Generating system core images
If the system crashes, it attempts to save a copy of its physical mem‐
ory to the swap area, to be copied to the file system after reboot (see
savecore(8)). To save a core image for a hung system, type on the con‐
sole (after control-P if necessary):
>>> I
>>> S C00
This resets the bus and jumps to the start of the dumping code. The
system will reboot automatically.
Examining system core images
Savecore saves in the dump directory two files: the copy of physical
memory, called vmcore.n, and a copy of the kernel binary unix.n, where
n is a sequence counter. To recover a stack traceback at the time of
the crash, type
$ adb unix.n vmcore.n
$<crash
$c
Pi(9.1) can examine kernel core dumps.
FILES
/unix default Unix kernel binary
/boot system bootstrap
SEE ALSO
fsck(8), init(8), rc(8)
BUGS
Our homemade boot ROM for Emulex disks always boots from drive 0, no
matter what you tell it.
REBOOT(8)