Give a short listing of the files in the root directory of the default boot device, as a hint about available boot files. (A ? may also be specified as the last segment of a path, in which case the listing will be of the relevant subdirectory.)
.Sm off bios_drive: interface( unit,[slice,part]) filename .Sm on [-aCcDdghmnPprsv] .Sm off [-S speed] .Sm on
Specify boot file and flags.
The drive number as recognized by the BIOS. 0 for the first drive, 1 for the second drive, etc.
The type of controller to boot from. Note that the controller is required to have BIOS support since the BIOS services are used to load the boot file image.
The supported interfaces are:
ST506, IDE, ESDI, RLL disks on a WD100 or lookalike controller
5 1/4" or 3 1/2" High density floppies
SCSI disk on any supported SCSI controller
The unit number of the drive on the interface being used. 0 for the first drive, 1 for the second drive, etc.
The partition letter inside the BSD portion of the disk. See bsdlabel(8). By convention, only partition a contains a bootable image. If sliced disks are used ("fdiskpartitions"), any slice (1 for the first slice, 2 for the second slice, etc.) can be booted from, with the default (if not specified) being the active slice or, otherwise, the first .Fx slice. If slice is specified as 0, the first .Fx slice (also known as "compatibility" slice) is booted from.
The pathname of the file to boot (relative to the root directory on the specified partition). Defaults to /boot/kernel/kernel. Symbolic links are not supported (hard links are).
.Sm off [-S speed] .Sm on
during kernel initialization, ask for the device to mount as the root file system.
try to mount root file system from a CD-ROM.
this flag is currently a no-op.
boot with the dual console configuration. In the single configuration, the console will be either the internal display or the serial port, depending on the state of the -h option below. In the dual console configuration, both the internal display and the serial port will become the console at the same time, regardless of the state of the -h option.
enter the DDB kernel debugger (see ddb(4)) as early as possible in kernel initialization.
use the GDB remote debugging protocol.
force the serial console. For instance, if you boot from the internal console, you can use the -h option to force the kernel to use the serial port as its console device. The serial port driver sio(4) has a flag (0x20) to override this option. If that flag is set, the serial port will always be used as the console, regardless of the -h option described here. See the man page for sio(4) for more details.
mute the console.
ignore key press to interrupt boot before loader(8) is invoked.
probe the keyboard. If no keyboard is found, the -D and -h options are automatically set.
pause after each attached device during the device probing phase.
use the statically configured default for the device containing the root file system (see config(8)). Normally, the root file system is on the device that the kernel was loaded from.
boot into single-user mode; if the console is marked as "insecure" (see ttys(5)), the root password must be entered.
-S speed .Sm on
set the speed of the serial console to speed. The default is 9600 unless it has been overridden by setting BOOT_COMCONSOLE_SPEED in /etc/make.conf and recompiling the boot blocks.
be verbose during device probing (and later).
You may put a BIOS drive number, a controller type, a unit number, a partition, a kernel file name, and any valid option in /boot.config to set defaults. Enter them in one line just as you type at the boot: prompt.
"NOTE": On older machines, or otherwise where EDD support (disk packet interface support) is not available, all boot-related files and structures (including the kernel) that need to be accessed during the boot phase must reside on the disk at or below cylinder 1023 (as the BIOS understands the geometry). When a "Disk error 0x1" is reported by the second-stage bootstrap, it generally means that this requirement has not been adhered to.