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:
Reboot normally logs the reboot using syslog(8) and places a shutdown record in the login accounting file (see utmp(5). 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, and unless this fails, the system will resume multi-user operations.
Cold starts. On an HP300, the boot procedure uses the boot rom to load a boot program from an LIF format directory at the beginning of an attached disk. The /usr/mdec directory contains a disk boot program bootrd which should be placed in a new pack automatically by newfs(8) when the ``a'' partition file system on the pack is created.
This boot program finds the corresponding file on the given device ( vmunix by default), loads that file into memory, and starts the program at the entry address specified in the program header.
The boot program can be interrupted by typing `^C' (ctrl-C). This will force the boot program to interactively prompt for a system to boot. If not interrupted, it will boot from the device from which the boot program itself was loaded.
The file specifications used for an interactive boot are of the form:
device(unit,minor)
where device is the type of the device to be searched, unit is 8 * the hpib number plus the unit number of the disk or tape, and minor is the disk partition or tape file number. Normal line editing characters can be used when typing the file specification. Currently, ``rd'' is the only valid device specifier.
For example, to boot from the `a' file system of unit 0 on HP-IB 2, type `rd(16,0)vmunix' to the boot prompt. For tapes, the minor device number gives a file offset.
In an emergency, the bootstrap methods described in the paper Installing 4.3bsd on the HP300 can be used to boot from a distribution tape.