108 lines
2.9 KiB
Groff
108 lines
2.9 KiB
Groff
.\" $NetBSD: console.4,v 1.7 2002/01/15 01:41:11 wiz Exp $
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.\"
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.Dd May 12, 2000
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.Os
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.Dt CONS 4 i386
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.Sh NAME
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.Nm console
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.Nd i386 console interface
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.Sh DESCRIPTION
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The
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.Dq console
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device is used for
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.Em kernel printf
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messages and accesses to the
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.Pa /dev/console
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character special device in user mode.
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It is attached to a hardware interface at boot time controlled by options
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in the kernel configuration file, or information passed by the boot loader.
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.Pp
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Bootblocks from
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.Nx 1.4
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or newer select their console device from a compiled-in list,
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and then pass their choice of console device and console parameters to
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the kernel.
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.Pp
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As of
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.Nx 1.5 ,
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the
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.Ic consdev
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bootblock command allows changing the console device on-the-fly.
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.Pp
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The kernel will use the same console device as the
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bootblock; no special kernel configuration is required.
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.Pp
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To override
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the bootblock's choice of console, or to use a serial kernel console
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with older bootblocks, you must specify kernel config-file options to
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override the information passed by the bootblock.
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The current option choices are:
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.Bl -tag -width aaa
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.It - the standard PC keyboard and display
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(with either the
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.Dq pc
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or the
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.Xr wscons 4
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driver)
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.It - standard PC serial ports
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(with
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.Xr com 4
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driver)
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.El
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.Pp
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The available
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.Em kernel configuration
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options are:
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.Bl -ohang
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.It Cd options CONSDEVNAME=string
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specifies the name of the console device. Valid values are
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.Dq pc
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for the pc keyboard / display (default)
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and
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.Dq com
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for a serial port.
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.It Cd options CONADDR=integer
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sets the base address for the serial console port (default: 0x3f8).
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.It Cd options CONSPEED=integer
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sets the baudrate for the serial console (default: 9600).
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.It Cd options CONS_OVERRIDE
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causes console information passed by the bootloader to be ignored and
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the settings specified by the three options above (or the defaults) to be
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used. Default behaviour is to use the settings from the bootloader if
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present, and to use option / default values only if no information was
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passed.
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.It Cd options CONMODE=integer
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allows to specify terminal control flags. The argument is a
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.Dq cflag
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value, see
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.Xr termios 4
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for details. Default is
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.Li (CREAD | CS8 | HUPCL)
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(8N1).
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This option takes always effect, because mode settings are not passed
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by the bootloader.
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.El
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.Sh FILES
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.Bl -tag -width /dev/console
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.It Pa /dev/console
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.It Pa /sys/arch/i386/conf/CONFIG
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.El
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.Sh EXAMPLES
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.Cd options \&"CONSDEVNAME=\e"com\e"",CONADDR=0x2f8,CONSPEED=19200
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.Sh SEE ALSO
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.Xr tty 4 ,
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.Xr boot 8 ,
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.Xr boot_console 8 ,
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.Xr config 8
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.Sh BUGS
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The console device is chosen early in system startup regardless
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if the specified driver / device is present in the system configuration file.
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If the driver asked for by the bootloader or
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.Dq Cd options CONSDEVNAME
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is not configured into the system, a panic is caused. Because there is
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no console device, no explaining message will be printed.
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If the driver is present, but the specific device instance not, kernel
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printf will work, but
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.Pa /dev/console
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becomes a dummy.
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