BOOT(8)

NAME
boot - system bootstrapping procedures

DESCRIPTION
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. The 386 PC AT clones attempt to boot the floppy disk drive A (otherwise known as drive 0) first, and failing that, attempt to boot the hard disk C (otherwise known as hard disk controller 1, drive 0). The automatic boot will attempt to load bsd from partition A of either the floppy or the hard disk. This boot may be aborted by typing any character on the keyboard repeatedly (four or five times at least) during the operating system load phase, after which the bootstrap will prompt for the file that you wish to load instead.

One exception to this is the ‘d’ key, which will not abort the load but instead silently force the DEBUG boot flags. The boot flags for an autoboot are 0, and 3 for the successive boot after an aborted autoboot sequence. No other provison is made for setting boot flags (yet). A specific device or bootstrap file may be used; for example,

The file specifications used for the boostrap when loaded with the “askme” flag (e.g. an aborted autoboot) are of the form:

    device unit partition:

where device is the type of the device, assumed to be on the ISA bus, to be searched, unit is the unit number of the disk or tape, and partition is the disk partition or tape file number. Normal line editing characters can be used when typing the file specification. The following list of supported devices may vary from installation to installation:

    wd	ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
    	controller
    fd	5 1/4" or 3 1/2" High density floppies

For example, to boot from a file system which starts at cylinder 0 of unit 0 of an IDE disk, type “wd0a:bsd” to the boot prompt; “fd0a:bsd” would specify a 3 1/2" floppy drive 0 .

In an emergency, the bootstrap methods described in the paper can be used to boot from a distribution tape.

FILES
/bsd
    system code
/boot
    system bootstrap

SEE ALSO
halt(8), reboot(8), shutdown(8)

BUGS
The disklabel format used by this version of BSD is quite different from that of other architectures.