The “console” device is used for
kernel printf messages and accesses to the
/dev/console character special device in user mode. It is attached to a hardware interface at boot time controlled by options in the kernel configuration file, or information passed by the boot loader.
Bootblocks from
NetBSD 1.4 or newer select their console device from a compiled-in list, and then pass their choice of console device and console parameters to the kernel.
As of
NetBSD 1.5, the
consdev bootblock command allows changing the console device on-the-fly.
The kernel will use the same console device as the bootblock; no special kernel configuration is required.
To override the bootblock's choice of console, or to use a serial kernel console with older bootblocks, you must specify kernel config-file options to override the information passed by the bootblock. The current option choices are:
- the standard PC keyboard and display
(with either the “pc” or the
wscons(4) driver)
- standard PC serial ports
The available
kernel configuration options are:
options CONSDEVNAME=string
specifies the name of the console device. Valid values are “pc” for the pc keyboard / display (default) and “com” for a serial port.
options CONADDR=integer
sets the base address for the serial console port (default: 0x3f8).
options CONSPEED=integer
sets the baudrate for the serial console (default: 9600).
options CONS_OVERRIDE
causes console information passed by the bootloader to be ignored and the settings specified by the three options above (or the defaults) to be used. Default behaviour is to use the settings from the bootloader if present, and to use option / default values only if no information was passed.
options CONMODE=integer
allows to specify terminal control flags. The argument is a “cflag” value, see
termios(4) for details. Default is
(CREAD |
CS8 |
HUPCL) (8N1). This option takes always effect, because mode settings are not passed by the bootloader.