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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
<sect1 id="ch-system-stripping">
<?dbhtml filename="stripping.html"?>
<title>Stripping</title>
<para>This section is optional. If the intended user is not a
programmer and does not plan to do
any debugging on the system software, the system size can be decreased
by about 2 GB by removing the debugging symbols and unneeded symbol table
entries from binaries and libraries. This causes no inconvenience other
than not being able to debug the software fully anymore.</para>
<para>Most people who use the commands mentioned below do not
experience any difficulties. However, it is easy to make a typo and
render the new system unusable, so before running the
<command>strip</command> commands, it is a good idea to make a
backup of the LFS system in its current state.</para>
<para>A <command>strip</command> command with
<parameter>--strip-unneeded</parameter> option removes all debug symbols
from a binary or library. And, it removes all symbol table entries not
needed by the linker (for static libraries) or dynamic linker (for
dynamic-linked binaries and shared libraries).</para>
<para>The debugging symbols for selected libraries are placed
in separate files. This debugging information is needed if running
regression tests that use <ulink
url='&blfs-book;/general/valgrind.html'>valgrind</ulink> or <ulink
url='&blfs-book;/general/gdb.html'>gdb</ulink> later in BLFS.
</para>
<para>Note that <command>strip</command> will overwrite the binary or library
file it is processing. This can crash the processes using code or data from
the file. If the process running <command>strip</command> itself is
affected, the binary or library being stripped can be destroyed and can
make the system completely unusable. To avoid it, we'll copy some libraries
and binaries into <filename class="directory">/tmp</filename>, strip them
there, and install them back with the <command>install</command> command.
Read the related entry in <xref linkend="pkgmgmt-upgrade-issues"/> for the
rationale to use the <command>install</command> command here.</para>
<note><para>The ELF loader's name is ld-linux-x86-64.so.2 on 64-bit systems
and ld-linux.so.2 on 32-bit systems. The construct below selects the
correct name for the current architecture, excluding anything ending
with <quote>g</quote>, in case the commands below have already been
run.</para></note>
<!-- also of interest are libgfortan, libgo, libgomp, and libobjc from GCC -->
<!--<screen><userinput>save_lib="ld-2.25.so libc-2.25.so libpthread-2.25.so libthread_db-1.0.so"-->
<screen><userinput>save_usrlib="$(cd /usr/lib; ls ld-linux*[^g])
libc.so.6
libthread_db.so.1
libquadmath.so.&libquadmath-version;
libstdc++.so.&libstdcpp-version;
libitm.so.&libitm-version;
libatomic.so.&libatomic-version;"
cd /usr/lib
for LIB in $save_usrlib; do
objcopy --only-keep-debug $LIB $LIB.dbg
cp $LIB /tmp/$LIB
strip --strip-unneeded /tmp/$LIB
objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
install -vm755 /tmp/$LIB /usr/lib
rm /tmp/$LIB
done
online_usrbin="bash find strip"
online_usrlib="libbfd-&binutils-version;.so
libhistory.so.&readline-soversion;
libncursesw.so.&ncurses-version;
libm.so.6
libreadline.so.&readline-soversion;
libz.so.&zlib-version;
$(cd /usr/lib; find libnss*.so* -type f)"
for BIN in $online_usrbin; do
cp /usr/bin/$BIN /tmp/$BIN
strip --strip-unneeded /tmp/$BIN
install -vm755 /tmp/$BIN /usr/bin
rm /tmp/$BIN
done
for LIB in $online_usrlib; do
cp /usr/lib/$LIB /tmp/$LIB
strip --strip-unneeded /tmp/$LIB
install -vm755 /tmp/$LIB /usr/lib
rm /tmp/$LIB
done
for i in $(find /usr/lib -type f -name \*.so* ! -name \*dbg) \
$(find /usr/lib -type f -name \*.a) \
$(find /usr/{bin,sbin,libexec} -type f); do
case "$online_usrbin $online_usrlib $save_usrlib" in
*$(basename $i)* )
;;
* ) strip --strip-unneeded $i
;;
esac
done
unset BIN LIB save_usrlib online_usrbin online_usrlib
</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
indicate that those files are scripts instead of binaries.</para>
</sect1>
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