[3c928f1] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[b06ca36] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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[81fd230] | 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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[ddd5542] | 7 |
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[8a269ec] | 8 | <sect1 id="ch-system-stripping">
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| 9 | <?dbhtml filename="stripping.html"?>
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[ddd5542] | 10 |
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[8a269ec] | 11 | <title>Stripping</title>
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[ddd5542] | 12 |
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[d672ab7] | 13 | <para>This section is optional. If the intended user is not a
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[c32384e] | 14 | programmer and does not plan to do
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[9c753b58] | 15 | any debugging of the system software, the system's size can be decreased
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| 16 | by some 2 GB by removing the debugging symbols, and some unnecessary symbol table
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| 17 | entries, from binaries and libraries. This causes no real inconvenience for
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| 18 | a typical Linux user.</para>
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[ddd5542] | 19 |
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[826bbcc] | 20 | <para>Most people who use the commands mentioned below do not
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[9c753b58] | 21 | experience any difficulties. However, it is easy to make a mistake and
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| 22 | render the new system unusable. So before running the
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[826bbcc] | 23 | <command>strip</command> commands, it is a good idea to make a
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[ddd5542] | 24 | backup of the LFS system in its current state.</para>
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| 25 |
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[9c753b58] | 26 | <para>A <command>strip</command> command with the
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[942e81de] | 27 | <parameter>--strip-unneeded</parameter> option removes all debug symbols
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[9c753b58] | 28 | from a binary or library. It also removes all symbol table entries not
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[942e81de] | 29 | needed by the linker (for static libraries) or dynamic linker (for
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[9c753b58] | 30 | dynamically linked binaries and shared libraries).</para>
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[942e81de] | 31 |
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[9c753b58] | 32 | <para>The debugging symbols from selected libraries are preserved
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| 33 | in separate files. That debugging information is needed to run
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| 34 | regression tests with <ulink
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[d672ab7] | 35 | url='&blfs-book;/general/valgrind.html'>valgrind</ulink> or <ulink
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[9c753b58] | 36 | url='&blfs-book;/general/gdb.html'>gdb</ulink> later, in BLFS.
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[c32384e] | 37 | </para>
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[6c8a79a] | 38 |
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[11d5dee] | 39 | <para>Note that <command>strip</command> will overwrite the binary or library
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[8a269ec] | 40 | file it is processing. This can crash the processes using code or data from
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[9c753b58] | 41 | the file. If the process running <command>strip</command> is
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| 42 | affected, the binary or library being stripped can be destroyed; this can
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| 43 | make the system completely unusable. To avoid this problem we copy some libraries
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[11d5dee] | 44 | and binaries into <filename class="directory">/tmp</filename>, strip them
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[9c753b58] | 45 | there, then reinstall them with the <command>install</command> command.
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| 46 | (The related entry in <xref linkend="pkgmgmt-upgrade-issues"/> gives the
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| 47 | rationale for using the <command>install</command> command here.)</para>
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[de28837] | 48 |
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[8ec5b53] | 49 | <note><para>The ELF loader's name may vary on different systems.
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| 50 | The construct below selects the
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[8731bd1] | 51 | correct name for the current architecture, excluding anything ending
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| 52 | with <quote>g</quote>, in case the commands below have already been
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| 53 | run.</para></note>
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[4350669] | 54 |
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[b595526] | 55 | <important>
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| 56 | <para>
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[04038ad] | 57 | If there is any package whose version is different from the version
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[b595526] | 58 | specified by the book (either following a security advisory or
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| 59 | satisfying personal preference), it may be necessary to update the
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[04038ad] | 60 | library file name in <envar>save_usrlib</envar> or
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[b595526] | 61 | <envar>online_usrlib</envar>.
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| 62 | <emphasis role='bold'>Failing to do so may render the system
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| 63 | completely unusable.</emphasis>
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| 64 | </para>
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| 65 | </important>
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| 66 |
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[77d2cd8d] | 67 | <!-- also of interest are libgfortan, libgo, libgomp, and libobjc from GCC -->
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[6c8a79a] | 68 |
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[00abb8f] | 69 | <!--<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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[8731bd1] | 70 | <screen><userinput>save_usrlib="$(cd /usr/lib; ls ld-linux*[^g])
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[adcaf07e] | 71 | libc.so.6
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[6094dae] | 72 | libthread_db.so.1
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[d672ab7] | 73 | libquadmath.so.&libquadmath-version;
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[6094dae] | 74 | libstdc++.so.&libstdcpp-version;
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[d672ab7] | 75 | libitm.so.&libitm-version;
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| 76 | libatomic.so.&libatomic-version;"
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[c32384e] | 77 |
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| 78 | cd /usr/lib
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| 79 |
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| 80 | for LIB in $save_usrlib; do
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| 81 | objcopy --only-keep-debug $LIB $LIB.dbg
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[ff96923] | 82 | cp $LIB /tmp/$LIB
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| 83 | strip --strip-unneeded /tmp/$LIB
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| 84 | objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
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| 85 | install -vm755 /tmp/$LIB /usr/lib
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| 86 | rm /tmp/$LIB
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[c32384e] | 87 | done
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| 88 |
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[de28837] | 89 | online_usrbin="bash find strip"
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[6094dae] | 90 | online_usrlib="libbfd-&binutils-version;.so
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[358ed3c] | 91 | libsframe.so.0.0.0
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[b83366b] | 92 | libhistory.so.&readline-soversion;
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[6094dae] | 93 | libncursesw.so.&ncurses-version;
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| 94 | libm.so.6
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[b83366b] | 95 | libreadline.so.&readline-soversion;
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[6094dae] | 96 | libz.so.&zlib-version;
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[d1592b9] | 97 | $(cd /usr/lib; find libnss*.so* -type f)"
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[de28837] | 98 |
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| 99 | for BIN in $online_usrbin; do
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| 100 | cp /usr/bin/$BIN /tmp/$BIN
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[08f72423] | 101 | strip --strip-unneeded /tmp/$BIN
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[de28837] | 102 | install -vm755 /tmp/$BIN /usr/bin
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| 103 | rm /tmp/$BIN
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| 104 | done
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[6c8a79a] | 105 |
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[de28837] | 106 | for LIB in $online_usrlib; do
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| 107 | cp /usr/lib/$LIB /tmp/$LIB
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| 108 | strip --strip-unneeded /tmp/$LIB
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| 109 | install -vm755 /tmp/$LIB /usr/lib
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| 110 | rm /tmp/$LIB
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| 111 | done
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[658dcab] | 112 |
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[08f72423] | 113 | for i in $(find /usr/lib -type f -name \*.so* ! -name \*dbg) \
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| 114 | $(find /usr/lib -type f -name \*.a) \
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| 115 | $(find /usr/{bin,sbin,libexec} -type f); do
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| 116 | case "$online_usrbin $online_usrlib $save_usrlib" in
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[d672ab7] | 117 | *$(basename $i)* )
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[11d5dee] | 118 | ;;
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[d672ab7] | 119 | * ) strip --strip-unneeded $i
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[11d5dee] | 120 | ;;
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[de28837] | 121 | esac
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| 122 | done
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| 123 |
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| 124 | unset BIN LIB save_usrlib online_usrbin online_usrlib
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| 125 | </userinput></screen>
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[3c928f1] | 126 |
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[9c753b58] | 127 | <para>A large number of files will be flagged as errors because their file
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| 128 | format is not recognized. These warnings can be safely ignored. They
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| 129 | indicate that those files are scripts, not binaries.</para>
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[6c8a79a] | 130 |
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[3c928f1] | 131 | </sect1>
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