<HTML ><HEAD ><TITLE >Create fallback position</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="Remote Serial Console HOWTO" HREF="index.html"><LINK REL="UP" TITLE="Preparation" HREF="preparation.html"><LINK REL="PREVIOUS" TITLE="Preparation" HREF="preparation.html"><LINK REL="NEXT" TITLE="Select a serial port " HREF="preparation-setport.html"></HEAD ><BODY CLASS="SECTION" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Remote Serial Console HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="preparation.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 2. Preparation</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="preparation-setport.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECTION" ><H1 CLASS="SECTION" ><A NAME="PREPARATION-FALLBACK" ></A >2.1. Create fallback position</H1 ><P >Good system administrators always have a viable fallback plan to cope with failures. A mistake configuring the serial console can make both the serial console and the attached monitor and keyboard unusable. A fallback plan is needed to retrieve console access.</P ><P >Many <SPAN CLASS="SYSTEMITEM" >Linux</SPAN > distributions allow boot diskettes to be created. Writing a boot diskette before altering the console configuration results in a boot diskette that passes good parameters to the kernel rather than parameters that may contain an error.</P ><P >Under <SPAN CLASS="PRODUCTNAME" >Red Hat Linux</SPAN > a boot diskette is created by determining the running kernel version</P ><DIV CLASS="INFORMALFIGURE" ><A NAME="PREPARATION-FALLBACK-KERNELVERSION" ></A ><P ></P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ><TT CLASS="PROMPT" >bash$</TT > <B CLASS="COMMAND" >uname -r</B > <TT CLASS="COMPUTEROUTPUT" >2.4.2-2</TT ></PRE ></FONT ></TD ></TR ></TABLE ><P ></P ></DIV ><P >and then using that version to create the boot diskette</P ><DIV CLASS="INFORMALFIGURE" ><A NAME="PREPARATION-FALLBACK-RHLDISK" ></A ><P ></P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ><TT CLASS="PROMPT" >bash#</TT > <B CLASS="COMMAND" >mkbootdisk --device /dev/fd0 2.4.2-2</B ></PRE ></FONT ></TD ></TR ></TABLE ><P ></P ></DIV ><P >Under <SPAN CLASS="PRODUCTNAME" >Debian <SPAN CLASS="ACRONYM" >GNU</SPAN >/Linux</SPAN > the boot diskette is created by determining the version of the running kernel and then using that version to write the boot diskette</P ><DIV CLASS="INFORMALFIGURE" ><A NAME="PREPARATION-FALLBACK-DEBIANDISK" ></A ><P ></P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" ><TT CLASS="PROMPT" >bash#</TT > <B CLASS="COMMAND" >mkboot /boot/vmlinuz-2.4.2-2</B ></PRE ></FONT ></TD ></TR ></TABLE ><P ></P ></DIV ><P >An alternative fallback position is have a rescue diskette with the machine. A common choice is <A HREF="http://www.toms.net/rb/" TARGET="_top" >Tom's root boot</A >.</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="preparation.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="preparation-setport.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Preparation</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="preparation.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Select a serial port</TD ></TR ></TABLE ></DIV ></BODY ></HTML >