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Diffstat (limited to 'chapter06')
| -rw-r--r-- | chapter06/chapter06.xml | 92 |
1 files changed, 88 insertions, 4 deletions
diff --git a/chapter06/chapter06.xml b/chapter06/chapter06.xml index c64770b2a..287b94540 100644 --- a/chapter06/chapter06.xml +++ b/chapter06/chapter06.xml @@ -502,11 +502,98 @@ Most likely something went wrong with the specs file amendment above.</para> &c6-gcc-2953; +<sect1 id="ch-system-aboutdebug"> +<title>About debugging symbols</title> +<?dbhtml filename="aboutdebug.html" dir="chapter06"?> + +<para>Most programs and libraries are, by default, compiled with debugging +symbols included (with <command>gcc</command>'s <emphasis>-g</emphasis> +option). This means that, when debugging a program or library that was compiled +with debugging information included, the debugger can give you not only memory +addresses but also the names of the routines and variables.</para> + +<para>The inclusion of these debugging symbols, however, enlarges a program or +library significantly. To get an idea of the amount of space these symbols +occupy, have a look at the following:</para> + +<itemizedlist> + +<listitem><para>a bash binary +with debugging symbols: 1200 KB</para></listitem> + +<listitem><para>a bash binary +without debugging symbols: 480 KB</para></listitem> + +<listitem><para>Glibc and GCC files (/lib and /usr/lib) +with debugging symbols: 87 MB</para></listitem> + +<listitem><para>Glibc and GCC files +without debugging symbols: 16 MB</para></listitem> + +</itemizedlist> + +<para>Sizes may vary somewhat, depending on which compiler was used and which C +library, but when comparing programs with and without debugging symbols the +difference will generally be a factor between 2 and 5.</para> + +<para>As most people will probably never use a debugger on their system +software, a lot of disk space can be regained by removing these symbols. For +your convenience, the next section shows how to strip all debugging symbols +from all programs and libraries. Information on other ways of optimizing your +system can be found in the hint at <ulink +url="&hints-root;optimization.txt"/>.</para> + +</sect1> + + +<sect1 id="ch-system-strippingagain"> +<title>Stripping again</title> +<?dbhtml filename="strippingagain.html" dir="chapter06"?> + +<para>If you are not a programmer and don't plan to do any debugging on your +system software, you can shrink your system by about 200 MB by removing the +debugging symbols from binaries and libraries. This causes no inconvenience +other than not being able to debug the software fully any more.</para> + +<para>Most people who use the command mentioned below don't experience any +problems. But it is easy to make a typo and render your new system unusable, so +before running the strip command it is probably a good idea to make a backup of +the current situation.</para> + +<para>If you are going to perform the stripping, special care is needed to +ensure you're not running any of the binaries that are about to be stripped. +If you're not sure whether you entered chroot with the command given in +<xref linkend="ch-system-chroot"/>, then now exit from chroot and reenter it +with the following commands:</para> + +<screen><userinput>logout; chroot $LFS /tools/bin/env -i \ + HOME=/root TERM=$TERM PS1='\u:\w\$ ' \ + PATH=/bin:/usr/bin:/sbin:/usr/sbin \ + /tools/bin/bash --login</userinput></screen> + +<para>Now you can safely strip the binaries and libraries:</para> + +<screen><userinput>/tools/bin/find /{,usr/}{bin,lib,sbin} -type f \ + -exec /tools/bin/strip --strip-debug '{}' ';'</userinput></screen> + +<para>A large number of files will be reported as having their file format not +recognized. These warnings can be safely ignored, they just mean that those +files are scripts instead of binaries, no harm is done.</para> + +<para>If you are really tight on disk space, you may want to use +<emphasis>--strip-all</emphasis> on the binaries in +<filename>/{,usr/}{bin,sbin}</filename> to gain several more megabytes. But do +<emphasis>not</emphasis> use this option on libraries: they would be +destroyed.</para> + +</sect1> + + <sect1 id="ch-system-revisedchroot"> <title>Revised chroot command</title> <?dbhtml filename="revisedchroot.html" dir="chapter06"?> -<para>From now on when you exit the chroot environment and wish to re-enter +<para>From now on when you exit the chroot environment and wish to reenter it, you should run the following modified chroot command:</para> <screen><userinput>chroot $LFS /usr/bin/env -i \ @@ -521,8 +608,5 @@ just yet. There is still some use for it towards the end of the book.</para> </sect1> - -&c6-aboutdebug; - </chapter> |