NAME
boot_console —
selection of a console
device in the x86 bootloader
DESCRIPTION
The
NetBSD x86 bootloader selects a console device for
its user interaction and passes information about it to the
NetBSD kernel. When booting from the system BIOS, the
console device and properties are saved in the primary bootstrap by
installboot(8). For
other boot procedures (such as
x86/dosboot(8)) the
selection process is controlled by bootloader compile-time options and system
setup at the bootloader startup time. The selection may be changed on-the-fly
from within the bootloader.
Serial Console Options
The compile-time options (to be set in the booter's “Makefile”) are:
- SUPPORT_SERIAL=policy
- enables support for serial input/output. By default this
option is not set and the standard PC keyboard and display are always used
as the console device. See
Console Selection
Policy below for valid values of policy.
- DIRECT_SERIAL
- causes direct hardware access to be used for serial input
/ output. With this option, software handshake (XON/XOFF) is used for flow
control. Without this option, BIOS functions are employed for serial port
handling, which require hardware handshake lines to be completely
wired.
- CONSPEED=integer
- sets the baud-rate for the serial console. This option
has only an effect when used in combination with the
“
DIRECT_SERIAL
” option above,
otherwise, the default setting of 9600 baud is used. The value of
integer must be something that makes sense as a
serial port baud rate.
- COMCONS_KEYPRESS
- Require a character input within seven (7) seconds from
serial console device to be selected.
Console Selection Policy
The actual policy for the console selection is determined by the value of
“
SUPPORT_SERIAL
” The following options are
available:
- CONSDEV_PC
- Force use of the standard PC keyboard and display as the
console.
- CONSDEV_COM0
...
CONSDEV_COM3
- Use the serial port with the corresponding BIOS number as
the console. No attempt is made to verify connectivity on the selected
port. If the port is not known to the BIOS, it falls back to
“
CONSDEV_PC
”. (Note: This feature can
be deliberately used for console selection if the serial ports have been
disabled in the BIOS.)
- CONSDEV_COM0KBD
...
CONSDEV_COM3KBD
- If the port is known to the BIOS, and output of a
character to the port succeeds (and if
“
DIRECT_SERIAL
” is defined the RS-232
“modem ready” status is on after the character is output), the
port is used as console. If the port is not known to the BIOS, or the test
output fails, it falls back to
“CONSDEV_PC
”.
- CONSDEV_AUTO
- Auto-select the console. All serial ports known to the
BIOS are probed in sequence. If output of a character to the port succeeds
(and if “
DIRECT_SERIAL
” is defined the
RS-232 “modem ready” status is on after the character is
output), the port is used as console. If no serial port passes the check,
“CONSDEV_PC
” is used. The progress of
the selection process is shown at the PC display as digits corresponding
to the serial port number currently probed.
FILES
-
-
- src/sys/arch/i386/stand/{boot,pxeboot}/Makefile
- compile time options for the boot programs.
SEE ALSO
console(4),
installboot(8),
x86/boot(8)
BUGS
The serial communication parameters (byte-size, parity, stop-bits) are not
settable (either at compile time or run time). The default parameters are
“8 N 1”.
The baud rate is not settable when using BIOS I/O. It should be settable at
compile time with “
CONSPEED
” just as it is
when using “
DIRECT_SERIAL
”. The default
speed is 9600 baud (the maximum for BIOS I/O).