diff --git a/books/bookvol4.pamphlet b/books/bookvol4.pamphlet
index 854dcf3..418aeb8 100644
--- a/books/bookvol4.pamphlet
+++ b/books/bookvol4.pamphlet
@@ -5241,6 +5241,33 @@ vector thus:
 Again we rerun the failing function and now tpd1 contains the
 domain vector for the domain CHAR:
 
+\subsection{Operating system level I/O trace (strace)}
+If the bug seems to happen during startup the only method of 
+debugging might be to use strace. To do this, replace the 
+\$AXIOM/bin/AXIOMsys binary with a shell script. You should:
+
+\begin{enumerate}
+\item rename \$AXIOM/bin/AXIOMsys to \$AXIOM/bin/AXIOMsys.bin
+\item create the shell script shown below
+\item copy the shell script to the file \$AXIOM/bin/AXIOMsys so it will 
+execute in place of the normal Axiom image
+\item chmod +x \$AXIOM/bin/AXIOMsys to make the script executable
+\item start axiom normally
+\end{enumerate}
+
+The script reads:
+\begin{verbatim}
+#!/bin/sh
+exec strace -o /tmp/str.$$ /research/test/mnt/ubuntu/bin/AXIOMsys.bin "$@" | tee /tmp/tee.$$
+\end{verbatim}
+
+The script will create 2 files in the tmp directory, "str.NNNNN" and
+"tee.NNNNN" where NNNNN is the process id assigned to axiom at runtime.
+
+The tee.NNNNN file contains the console output you saw.
+The str.NNNNN contains the output of strace which is a list of all of
+the system calls and their result.
+
 \section{How to make graphs in algebra books}
 dot -Tps <pic >books/ps/domain.ps
 
diff --git a/changelog b/changelog
index a907e36..5f5033c 100644
--- a/changelog
+++ b/changelog
@@ -1,3 +1,5 @@
+20101127 tpd src/axiom-website/patches.html 20101127.01.tpd.patch
+20101127 tpd books/bookvol4 add debugging technique
 20101126 tpd src/axiom-website/patches.html 20101126.01.tpd.patch
 20101126 tpd src/interp/postprop.lisp treeshake compiler
 20101126 tpd src/interp/compiler.lisp treeshake compiler
diff --git a/src/axiom-website/patches.html b/src/axiom-website/patches.html
index 76248d1..3708f26 100644
--- a/src/axiom-website/patches.html
+++ b/src/axiom-website/patches.html
@@ -3276,5 +3276,7 @@ books/bookvol9 treeshake compiler<br/>
 books/bookvol9 treeshake compiler<br/>
 <a href="patches/20101126.01.tpd.patch">20101126.01.tpd.patch</a>
 books/bookvol9 treeshake compiler<br/>
+<a href="patches/20101127.01.tpd.patch">20101127.01.tpd.patch</a>
+books/bookvol4 add debugging technique<br/>
  </body>
 </html>