NAME

reboot − UNIX bootstrapping procedures

SYNOPSIS

/etc/reboot [ −n ] [ −q ]

DESCRIPTION

UNIX is started by placing it in memory at location zero and transferring to zero.  Since the system is not reenterable, it is necessary to read it in from disk or tape each time it is to be bootstrapped. 

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 /etc/reboot can be used.  Reboot causes the disks to be synced, and then a multi-user reboot (as described below) is 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 processor is on fire.  (It is no longer necessary to reboot after rebuilding the root file system.) 

−q reboots quickly and ungracefully, without shutting down running processes first. 

Power fail and crash recovery.  Normally, the system will reboot itself at power-up or after crashes.  Provided the auto-restart is enabled on the machine front panel, an automatic consistency check of the file systems will be performed then and unless this fails the system will resume multi-user operations. 

Cold starts.  These are processor type dependent.  On an 11/780, there are two floppy files for each disk controller, both of which cause boots from unit 0 of the root file system of a controller located on mba0 or uba0.  One gives a single user shell, while the other invokes the multi-user automatic reboot.  Thus these files are HPS and HPM for the single and multi-user boot from MASSBUS RP06/RM03/RM05 disks, UPS and UPM for UNIBUS storage module controller and disks such as the EMULEX SC-21 and AMPEX 9300 pair, or HKS and HKM for RK07 disks. 

Giving the command

>>>BOOT HPM

Would boot the system from (e.g.) an RP06 and run the automatic consistency check as described in fsck(8). (Note that it may be necessary to type control-P to gain the attention of the LSI-11 before getting the >>> prompt.) The command

>>>BOOT ANY

invokes a version of the boot program in a way which allows you to specify any system as the system to be booted.  It reads from the console a device specification (see below) followed immediately by a pathname. 

On an 11/750, the reset button will boot from the device selected by the front panel boot device switch.  In systems with RK07’s, position B normally selects the RK07 for boot.  This will boot multi-user.  To boot from RK07 with boot flags you may specify

>>>B/n DMA0

where, giving a n of 1 causes the boot program to ask for the name of the system to be bootstrapped, giving a n of 2 causes the boot program to come up single user, and a n of 3 causes both of these actions to occur. 

The 11/750 boot procedure uses the boot roms to load block 0 off of the specified device.  The /usr/mdec directory contains a number of bootstrap programs for the various disks which should be placed in a new pack via

cp /usr/mdec/xxboot /dev/xx?a

whenever a new bootable pack is to be created. 

On both processors, the boot program finds the corresponding file on the given device, loads that file into memory location zero, and starts the program at the entry address specified in the program header (after clearing off the high bit of the specified entry address.)  Normal line editing characters can be used in specifying the pathname. 

If you have an rp06, rm05 or rm03 disk and wish to boot off of a file system which starts at cylinder 0 of unit 0, you can type “hp(0,0)vmunix” to the boot prompt; “up(0,0)vmunix” would specify a UNIBUS ampex 9300 drive, “rk(0,0)vmunix” would specify a RK-07 disk drive. 

A device specification has the following form:

device(unit, minor)

where device is the type of the device to be searched, unit is 8\(** the mba or uba number plus the unit number of the device, and minor is the minor device index.  The following list of supported devices may vary from installation to installation:

hpRP06, RM03, RM05, RP07 or RM80 on MASSBUS
upstorage module drive on UNIBUS
htTE16,TU45,TU77 on MASSBUS
hkRK07 on UNIBUS
tmTM11 emulation tape drives on UNIBUS
tsTS11 on UNIBUS

For tapes, the minor device number gives a file offset. 

In an emergency, the bootstrap methods described in the paper “Setting up the Fourth Berkeley Software Tape” can be used to boot from a distribution tape. 

FILES

/vmunixsystem code
/bootsystem bootstrap

SEE ALSO

crash(8), fsck(8), init(8), rc(8), shutdown(8), halt(8)

4th Berkeley Distribution  —  @(#)reboot.8 1.1 Preliminary GER0