[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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[ddd5542] | 15 | any debugging on the system software, the system size can be decreased
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[942e81de] | 16 | by about 2 GB by removing the debugging symbols and unneeded symbol table
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| 17 | entries from binaries and libraries. This causes no inconvenience other
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| 18 | than not being able to debug the software fully anymore.</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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[ddd5542] | 21 | experience any difficulties. However, it is easy to make a typo 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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[942e81de] | 26 | <para>A <command>strip</command> command with
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| 27 | <parameter>--strip-unneeded</parameter> option removes all debug symbols
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| 28 | from a binary or library. And, it removes all symbol table entries not
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| 29 | needed by the linker (for static libraries) or dynamic linker (for
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| 30 | dynamic-linked binaries and shared libraries).</para>
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| 31 |
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[de28837] | 32 | <para>The debugging symbols for selected libraries are placed
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[d672ab7] | 33 | in separate files. This debugging information is needed if running
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| 34 | regression tests that use <ulink
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| 35 | url='&blfs-book;/general/valgrind.html'>valgrind</ulink> or <ulink
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[826bbcc] | 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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[11d5dee] | 41 | the file. If the process running <command>strip</command> itself is
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[8a269ec] | 42 | affected, the binary or library being stripped can be destroyed and can
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[11d5dee] | 43 | make the system completely unusable. To avoid it, we'll copy some libraries
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| 44 | and binaries into <filename class="directory">/tmp</filename>, strip them
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[de28837] | 45 | there, and install them back with the <command>install</command> command.
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| 46 | Read the related entry in <xref linkend="pkgmgmt-upgrade-issues"/> for the
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| 47 | rationale to use the <command>install</command> command here.</para>
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| 48 |
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[a3d6232] | 49 | <note><para>The ELF loader's name is ld-linux-x86-64.so.2 on 64-bit systems
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[bcb20b4] | 50 | and ld-linux.so.2 on 32-bit systems. 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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[77d2cd8d] | 55 | <!-- also of interest are libgfortan, libgo, libgomp, and libobjc from GCC -->
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[6c8a79a] | 56 |
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[00abb8f] | 57 | <!--<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] | 58 | <screen><userinput>save_usrlib="$(cd /usr/lib; ls ld-linux*[^g])
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[adcaf07e] | 59 | libc.so.6
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[6094dae] | 60 | libthread_db.so.1
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[d672ab7] | 61 | libquadmath.so.&libquadmath-version;
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[6094dae] | 62 | libstdc++.so.&libstdcpp-version;
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[d672ab7] | 63 | libitm.so.&libitm-version;
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| 64 | libatomic.so.&libatomic-version;"
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[c32384e] | 65 |
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| 66 | cd /usr/lib
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| 67 |
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| 68 | for LIB in $save_usrlib; do
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| 69 | objcopy --only-keep-debug $LIB $LIB.dbg
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[ff96923] | 70 | cp $LIB /tmp/$LIB
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| 71 | strip --strip-unneeded /tmp/$LIB
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| 72 | objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
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| 73 | install -vm755 /tmp/$LIB /usr/lib
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| 74 | rm /tmp/$LIB
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[c32384e] | 75 | done
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| 76 |
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[de28837] | 77 | online_usrbin="bash find strip"
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[6094dae] | 78 | online_usrlib="libbfd-&binutils-version;.so
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[b83366b] | 79 | libhistory.so.&readline-soversion;
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[6094dae] | 80 | libncursesw.so.&ncurses-version;
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| 81 | libm.so.6
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[b83366b] | 82 | libreadline.so.&readline-soversion;
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[6094dae] | 83 | libz.so.&zlib-version;
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[d1592b9] | 84 | $(cd /usr/lib; find libnss*.so* -type f)"
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[de28837] | 85 |
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| 86 | for BIN in $online_usrbin; do
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| 87 | cp /usr/bin/$BIN /tmp/$BIN
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[08f72423] | 88 | strip --strip-unneeded /tmp/$BIN
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[de28837] | 89 | install -vm755 /tmp/$BIN /usr/bin
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| 90 | rm /tmp/$BIN
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| 91 | done
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[6c8a79a] | 92 |
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[de28837] | 93 | for LIB in $online_usrlib; do
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| 94 | cp /usr/lib/$LIB /tmp/$LIB
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| 95 | strip --strip-unneeded /tmp/$LIB
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| 96 | install -vm755 /tmp/$LIB /usr/lib
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| 97 | rm /tmp/$LIB
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| 98 | done
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[658dcab] | 99 |
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[08f72423] | 100 | for i in $(find /usr/lib -type f -name \*.so* ! -name \*dbg) \
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| 101 | $(find /usr/lib -type f -name \*.a) \
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| 102 | $(find /usr/{bin,sbin,libexec} -type f); do
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| 103 | case "$online_usrbin $online_usrlib $save_usrlib" in
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[d672ab7] | 104 | *$(basename $i)* )
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[11d5dee] | 105 | ;;
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[d672ab7] | 106 | * ) strip --strip-unneeded $i
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[11d5dee] | 107 | ;;
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[de28837] | 108 | esac
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| 109 | done
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| 110 |
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| 111 | unset BIN LIB save_usrlib online_usrbin online_usrlib
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| 112 | </userinput></screen>
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[3c928f1] | 113 |
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[ddd5542] | 114 | <para>A large number of files will be reported as having their file
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[8a269ec] | 115 | format not recognized. These warnings can be safely ignored. They
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| 116 | indicate that those files are scripts instead of binaries.</para>
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[6c8a79a] | 117 |
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[3c928f1] | 118 | </sect1>
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