459 lines
7.8 KiB
HTML
459 lines
7.8 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>Optionally configure the BIOS</TITLE
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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TITLE="Remote Serial Console HOWTO"
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TITLE="Configure the terminal or the terminal emulator"
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HREF="preparation-terminal.html"><LINK
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TITLE="Configure the boot loader"
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HREF="configure-boot-loader.html"></HEAD
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Remote Serial Console HOWTO</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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>Prev</A
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><DIV
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CLASS="CHAPTER"
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><H1
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><A
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NAME="BIOS"
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></A
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>Chapter 3. Optionally configure the <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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></H1
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><P
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>Some <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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>s provide support for serial
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consoles. If your computer's <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> is one of
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these you should investigate the extent of the support provided.
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Depending upon the extent of serial console support you may not need
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to explicitly configure the boot loader to use the serial
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port.</P
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><P
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>The contributors to this <I
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CLASS="CITETITLE"
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>HOWTO</I
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> have
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encountered the following styles of <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> support
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for serial consoles.</P
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><P
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></P
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><DIV
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CLASS="VARIABLELIST"
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><DL
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><DT
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>Redirection of textual VGA output to the serial port</DT
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><DD
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><P
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>The <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> takes the interrupt 0x10
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<SPAN
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CLASS="QUOTE"
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>"video"</SPAN
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> requests used to write to the screen and
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sends the characters that would have appeared on the screen to
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the serial port. Characters recieved from the serial port are
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used to supply characters to <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> interrupt
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0x16 <SPAN
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CLASS="QUOTE"
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>"read key"</SPAN
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> requests.</P
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><P
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>Any 16-bit application which uses the
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<SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> functions for outputing text to the
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screen and reading from the keyboard is redirected to the serial
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port. This includes the <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> itself, the boot
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loader, and 16-bit operating systems (such as
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<SPAN
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CLASS="PRODUCTNAME"
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><SPAN
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CLASS="ACRONYM"
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>MS-DOS</SPAN
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></SPAN
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>).</P
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><P
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>When a 32-bit operating system (such as <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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>, <SPAN
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CLASS="SYSTEMITEM"
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>BSD</SPAN
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> or <SPAN
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CLASS="SYSTEMITEM"
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>Windows NT/2000/XP</SPAN
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>) loads the 16-bit
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<SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> is no longer accessible and the
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<SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> can no longer be used for input and
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output. The 32-bit operating system loads its own device drivers
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for this purpose. These device drivers then need to provide the
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redirection of console <SPAN
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CLASS="ACRONYM"
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>I/O</SPAN
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> to the serial
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port.</P
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><P
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>If your <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> uses this technique then
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you should:</P
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><DIV
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CLASS="PROCEDURE"
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><OL
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TYPE="1"
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><LI
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><P
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>Configure the <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> to redirect
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keyboard input and video output to the serial port.</P
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></LI
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><LI
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><P
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>Do not configure the boot loader, as the
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<SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> will redirect this 16-bit application's
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input and output to the serial port.</P
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></LI
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><LI
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><P
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>Configure <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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>
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to use the serial port as a console, as <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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> is a 32-bit operating
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system.</P
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></LI
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></OL
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></DIV
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></DD
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><DT
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><SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> configuration and power on self-test
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uses the serial port</DT
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><DD
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><P
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>These <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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>s use the serial port for
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configuration and the power-on self-test, but do not redirect the
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interrupt 0x10 <SPAN
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CLASS="QUOTE"
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>"video"</SPAN
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> requests interrupt 0x16
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<SPAN
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CLASS="QUOTE"
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>"read key"</SPAN
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> requests to the serial port.</P
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><P
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>Some <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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>s which usually redirect all
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keyboard and video output to the serial port can be configured in
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only to redirect <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> input and output. Look
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for a <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> configuration option similar to
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<SPAN
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CLASS="GUIMENUITEM"
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>Cease redirection after boot</SPAN
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>.</P
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><P
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>If your <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> uses this technique or you
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choose to set <SPAN
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CLASS="GUIMENUITEM"
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>Cease redirection after
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boot</SPAN
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> then you should:</P
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><DIV
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CLASS="PROCEDURE"
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><OL
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TYPE="1"
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><LI
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><P
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>Configure the <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> to send its output
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to the serial port.</P
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></LI
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><LI
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><P
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>Configure the boot loader to use the serial port.</P
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></LI
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><LI
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><P
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>Configure <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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>
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to use the serila port as the console, as <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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> is a 32-bit operating
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system.</P
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></LI
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></OL
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></DIV
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></DD
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><DT
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>Redirection of graphical <SPAN
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CLASS="ACRONYM"
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>VGA</SPAN
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> output to
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the serial port</DT
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><DD
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><P
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>Some graphical 32-bit operating systems do not provide
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their own facilities to send console output to the serial port.
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Some BIOSs attempt to overcome this shortcoming, using a
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propietary serial protocol to send graphical output to a remote
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serial client.</P
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><P
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>As these machines cannot be connected to from a standard
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terminal emulator this facility is best left unconfigured when
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using the <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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> operating
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system.</P
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><DIV
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CLASS="PROCEDURE"
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><OL
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TYPE="1"
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><LI
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><P
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>Configure the <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> not to send output
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to the serial port.</P
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></LI
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><LI
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><P
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>Configure the boot loader to use the serial port.</P
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></LI
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><LI
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><P
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>Configure <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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>
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to use the serial port as the console.</P
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></LI
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></OL
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></DIV
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></DD
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><DT
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>No serial port facilities</DT
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><DD
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><P
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>The <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> cannot be accessed from the
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serial port, so power-on self-test messages cannot be
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seen.</P
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><P
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>Note that <SPAN
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CLASS="ACRONYM"
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>BIOS</SPAN
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> may still be able to be
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configured remotely using the <TT
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CLASS="FILENAME"
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>/dev/nvram</TT
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> device. This takes some
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care.</P
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><DIV
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CLASS="PROCEDURE"
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><OL
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TYPE="1"
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><LI
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><P
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>Configure the boot loader to use the serial port.</P
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></LI
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><LI
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><P
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>Configure <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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>
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to use the serial port as the console.</P
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></LI
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></OL
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></DIV
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></DD
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></DL
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></DIV
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><P
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>If you need to configure the boot loader to use the serial
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port then continue to <A
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HREF="configure-boot-loader.html"
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>Chapter 4</A
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>.
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Otherwise go directly to <A
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HREF="configure-kernel.html"
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>Chapter 5</A
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> to
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configure the kernel; this is done by configuring the boot loader to
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pass boot parameters to the <SPAN
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CLASS="SYSTEMITEM"
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>Linux</SPAN
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> kernel.</P
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></DIV
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