boot_console(8) - NetBSD Manual Pages

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BOOT_CONSOLE(8)       NetBSD/x86 System Manager's Manual       BOOT_CONSOLE(8)


NAME

     boot_console -- selection of a console device in the x86 bootloader


DESCRIPTION

     The NetBSD x86 bootloader selects a console device for its user interac-
     tion 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 com-
     pile-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 con-
     sole 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 han-
     dling, 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 parame-
     ters 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).

NetBSD 10.0                    February 17, 2017                   NetBSD 10.0