123 lines
4.3 KiB
Groff
123 lines
4.3 KiB
Groff
.\" $NetBSD: boot_console.8,v 1.7 2000/11/07 05:44:17 lukem Exp $
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.\"
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.Dd May 12, 2000
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.Os
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.Dt BOOT_CONSOLE 8 i386
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.Sh NAME
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.Nm boot_console
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.Nd selection of a console device in the i386 bootloader
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.\"
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.Sh DESCRIPTION
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The
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.Nx
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i386 bootloader selects a console device for its user interaction and
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passes information about it to the
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.Nx
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kernel. The selection process is controlled by bootloader compile-time
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options and system setup at the bootloader startup time, and may
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be changed on-the-fly from within the bootloader.
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.\"
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.Ss Serial Console Options
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The compile-time options (to be set in the booter's
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.Dq Makefile )
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are:
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.Bl -ohang
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.It Dv Sy SUPPORT_SERIAL= Ns Fa policy
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enables support for serial input / output. By default this option is
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not set and the standard PC keyboard and display are always used as the
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console device. See
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.Dq Em "Console selection Policy"
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below for valid values of
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.Fa policy .
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.It Dv Sy DIRECT_SERIAL
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causes direct hardware access to be used for serial input / output.
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With this option, software handshake (XON/XOFF) is used for flow
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control. Without this option, BIOS functions are employed for serial
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port handling, which require hardware handshake lines to be completely
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wired.
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.It Dv Sy CONSPEED= Ns Fa integer
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sets the baud-rate for the serial console. This option has only an
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effect when used in combination with the
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.Dq Dv DIRECT_SERIAL
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option above, otherwise, the default setting of 9600 baud is used. The
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value of
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.Fa integer
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must be something that makes sense as a serial port baud rate.
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.It Dv Sy COMCONS_KEYPRESS
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Require a character input within seven (7) seconds from serial console
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device to be selected.
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.El
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.\"
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.Ss Console Selection Policy
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The actual policy for the console selection is determined by the value
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of
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.Dv Dq SUPPORT_SERIAL
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The following options are available:
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.Bl -ohang
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.It Dv Em CONSDEV_PC
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Force use of the standard PC keyboard and display as the console.
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.It Dv Em CONSDEV_COM0 Li ... Dv Em CONSDEV_COM3
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Use the serial port with the corresponding BIOS number as the console.
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No output is attempted to the selected serial port. If the port is not
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known to the BIOS, it falls back to
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.Dq Dv CONSDEV_PC .
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(Note: This feature can be deliberately used for console selection if
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the serial ports have been disabled in the BIOS.)
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.It Dv Em CONSDEV_COM0KBD Li ... Dv Em CONSDEV_COM3KBD
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If the port is known to the BIOS, and output of a character to the port
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succeeds (and if
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.Dq Dv DIRECT_SERIAL
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is defined the RS-232
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.Dq "modem ready"
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status is on after the character is output), the port is used as
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console. If the port is not known to the BIOS, it falls back to
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.Dq Dv CONSDEV_PC .
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.It Dv Em CONSDEV_AUTO
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Auto-select the console. All serial ports known to the BIOS are probed
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in sequence. If output of a character to the port succeeds (and if
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.Dq Dv DIRECT_SERIAL
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is defined the RS-232
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.Dq "modem ready"
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status is on after the character is output), the port is used as console.
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If no serial port passes the check,
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.Dq Dv CONSDEV_PC
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is used. The progress of the selection process is shown at the PC
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display as digits corresponding to the serial port number currently
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probed.
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.El
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.\"
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.Sh FILES
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.Bl -tag -width /sys/arch/i386/stand/{bios,dos,net}boot/Makefile
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.It Pa /sys/arch/i386/stand/{bios,dos,net}boot/Makefile
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compile time options for the boot programs.
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.El
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.\"
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.Sh SEE ALSO
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.Xr console 4 ,
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.Xr boot 8
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.\"
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.Sh BUGS
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The value of
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.Dv SERIAL_POLICY
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should be settable through a boot configuration option. However
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traditionally there was no non-volatile storage available on the PC
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platform. This requires console auto-selection methods which can be
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inconvenient and / or unstable in some situations. The selection policy
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should be adapted to the local hardware configuration, which might
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require code changes. (Some BIOS versions, particularly those used on
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large servers and in embedded and single-board industrial computers,
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have integrated support for serial consoles. The boot loader should
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query for these settings if possible.)
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.Pp
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The serial communication parameters (byte-size, parity, stop-bits) are
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not settable (either at compile time or run time). The default
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parameters are
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.Dq "8 N 1" .
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.Pp
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The baud rate is not settable when using BIOS I/O. It should be
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settable at compile time with
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.Dv Dq CONSPEED
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just as it is when using
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.Dv Dq DIRECT_SERIAL .
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The default speed is 9600 baud (the maximum for BIOS I/O).
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