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