[7152faa] | 1 | <?xml version="1.0" encoding="UTF-8"?>
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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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[80da60f] | 32 | <!-- TODO: Zstd is better than Zlib for both speed and size.
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| 33 | Unfortunately Valgrind does not support Zstd-compressed debug
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| 34 | info yet: https://bugs.kde.org/show_bug.cgi?id=469782 -->
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| 35 | <para>The debugging symbols from selected libraries are compressed with
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| 36 | <application>Zlib</application> and preserved in separate files. That
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| 37 | debugging information is needed to run regression tests with <ulink
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[d672ab7] | 38 | url='&blfs-book;/general/valgrind.html'>valgrind</ulink> or <ulink
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[9c753b58] | 39 | url='&blfs-book;/general/gdb.html'>gdb</ulink> later, in BLFS.
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[c32384e] | 40 | </para>
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[6c8a79a] | 41 |
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[11d5dee] | 42 | <para>Note that <command>strip</command> will overwrite the binary or library
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[8a269ec] | 43 | file it is processing. This can crash the processes using code or data from
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[9c753b58] | 44 | the file. If the process running <command>strip</command> is
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| 45 | affected, the binary or library being stripped can be destroyed; this can
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| 46 | make the system completely unusable. To avoid this problem we copy some libraries
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[11d5dee] | 47 | and binaries into <filename class="directory">/tmp</filename>, strip them
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[9c753b58] | 48 | there, then reinstall them with the <command>install</command> command.
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| 49 | (The related entry in <xref linkend="pkgmgmt-upgrade-issues"/> gives the
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| 50 | rationale for using the <command>install</command> command here.)</para>
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[de28837] | 51 |
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[a3d6232] | 52 | <note><para>The ELF loader's name is ld-linux-x86-64.so.2 on 64-bit systems
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[bcb20b4] | 53 | and ld-linux.so.2 on 32-bit systems. The construct below selects the
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[8731bd1] | 54 | correct name for the current architecture, excluding anything ending
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[ee950a5e] | 55 | with <literal>g</literal>, in case the commands below have already been
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[8731bd1] | 56 | run.</para></note>
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[4350669] | 57 |
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[b595526] | 58 | <important>
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| 59 | <para>
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[04038ad] | 60 | If there is any package whose version is different from the version
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[b595526] | 61 | specified by the book (either following a security advisory or
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| 62 | satisfying personal preference), it may be necessary to update the
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[04038ad] | 63 | library file name in <envar>save_usrlib</envar> or
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[b595526] | 64 | <envar>online_usrlib</envar>.
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| 65 | <emphasis role='bold'>Failing to do so may render the system
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| 66 | completely unusable.</emphasis>
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| 67 | </para>
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| 68 | </important>
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| 69 |
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[6dfcfecc] | 70 | <!-- also of interest are libgfortan, libgo, libgomp, and libobjc from GCC -->
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[6c8a79a] | 71 |
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[00abb8f] | 72 | <!--<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] | 73 | <screen><userinput>save_usrlib="$(cd /usr/lib; ls ld-linux*[^g])
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[adcaf07e] | 74 | libc.so.6
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[6094dae] | 75 | libthread_db.so.1
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[d672ab7] | 76 | libquadmath.so.&libquadmath-version;
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[6094dae] | 77 | libstdc++.so.&libstdcpp-version;
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[d672ab7] | 78 | libitm.so.&libitm-version;
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| 79 | libatomic.so.&libatomic-version;"
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[c32384e] | 80 |
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| 81 | cd /usr/lib
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| 82 | for LIB in $save_usrlib; do
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[80da60f] | 83 | objcopy --only-keep-debug --compress-debug-sections=zlib $LIB $LIB.dbg
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[ff96923] | 84 | cp $LIB /tmp/$LIB
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| 85 | strip --strip-unneeded /tmp/$LIB
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| 86 | objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
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| 87 | install -vm755 /tmp/$LIB /usr/lib
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| 88 | rm /tmp/$LIB
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[6dfcfecc] | 89 | done</userinput>
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| 90 | <userinput arch="ml_32,ml_all">
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[0ebda11] | 91 | cd /usr/lib32
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[6dfcfecc] | 92 | for LIB in $save_usrlib; do
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[3388c22] | 93 | objcopy --only-keep-debug $LIB $LIB.dbg
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| 94 | cp $LIB /tmp/$LIB
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| 95 | strip --strip-unneeded /tmp/$LIB
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| 96 | objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
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| 97 | install -vm755 /tmp/$LIB /usr/lib32
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| 98 | rm /tmp/$LIB
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[6dfcfecc] | 99 | done</userinput>
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| 100 | <userinput arch="ml_x32,ml_all">
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[0ebda11] | 101 | cd /usr/libx32
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[6dfcfecc] | 102 | for LIB in $save_usrlib; do
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[3388c22] | 103 | objcopy --only-keep-debug $LIB $LIB.dbg
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| 104 | cp $LIB /tmp/$LIB
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| 105 | strip --strip-unneeded /tmp/$LIB
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| 106 | objcopy --add-gnu-debuglink=$LIB.dbg /tmp/$LIB
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| 107 | install -vm755 /tmp/$LIB /usr/libx32
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| 108 | rm /tmp/$LIB
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[6dfcfecc] | 109 | done</userinput><userinput>
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[b3f1ebb3] | 110 |
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[de28837] | 111 | online_usrbin="bash find strip"
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[6094dae] | 112 | online_usrlib="libbfd-&binutils-version;.so
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[be5b2e0] | 113 | libsframe.so.&libsframe-version;
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[b83366b] | 114 | libhistory.so.&readline-soversion;
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[6094dae] | 115 | libncursesw.so.&ncurses-version;
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| 116 | libm.so.6
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[b83366b] | 117 | libreadline.so.&readline-soversion;
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[6094dae] | 118 | libz.so.&zlib-version;
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[b1b9182] | 119 | libzstd.so.&zstd-version;
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[d1592b9] | 120 | $(cd /usr/lib; find libnss*.so* -type f)"
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[de28837] | 121 |
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| 122 | for BIN in $online_usrbin; do
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| 123 | cp /usr/bin/$BIN /tmp/$BIN
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[08f72423] | 124 | strip --strip-unneeded /tmp/$BIN
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[de28837] | 125 | install -vm755 /tmp/$BIN /usr/bin
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| 126 | rm /tmp/$BIN
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| 127 | done
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[6c8a79a] | 128 |
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[de28837] | 129 | for LIB in $online_usrlib; do
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| 130 | cp /usr/lib/$LIB /tmp/$LIB
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| 131 | strip --strip-unneeded /tmp/$LIB
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| 132 | install -vm755 /tmp/$LIB /usr/lib
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| 133 | rm /tmp/$LIB
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[85cd74c2] | 134 | done</userinput><userinput arch="ml_32,ml_all">
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| 135 | for LIB in $online_usrlib; do
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| 136 | cp /usr/lib32/$LIB /tmp/$LIB
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| 137 | strip --strip-unneeded /tmp/$LIB
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| 138 | install -vm755 /tmp/$LIB /usr/lib32
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| 139 | rm /tmp/$LIB
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| 140 | done</userinput><userinput arch="ml_x32,ml_all">
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| 141 | for LIB in $online_usrlib; do
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| 142 | cp /usr/libx32/$LIB /tmp/$LIB
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| 143 | strip --strip-unneeded /tmp/$LIB
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| 144 | install -vm755 /tmp/$LIB /usr/libx32
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| 145 | rm /tmp/$LIB
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| 146 | done</userinput><userinput>
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[658dcab] | 147 |
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[08f72423] | 148 | for i in $(find /usr/lib -type f -name \*.so* ! -name \*dbg) \
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| 149 | $(find /usr/lib -type f -name \*.a) \
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| 150 | $(find /usr/{bin,sbin,libexec} -type f); do
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| 151 | case "$online_usrbin $online_usrlib $save_usrlib" in
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[d672ab7] | 152 | *$(basename $i)* )
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[11d5dee] | 153 | ;;
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[d672ab7] | 154 | * ) strip --strip-unneeded $i
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[11d5dee] | 155 | ;;
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[de28837] | 156 | esac
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[85cd74c2] | 157 | done</userinput><userinput arch="ml_32,ml_all">
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[9282602] | 158 | for i in $(find /usr/lib32 -type f -name \*.so* ! -name \*dbg) \
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| 159 | $(find /usr/lib32 -type f -name \*.a); do
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[3330d51] | 160 | case "$online_usrbin $online_usrlib $save_usrlib" in
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[b8d5542] | 161 | *$(basename $i)* )
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| 162 | ;;
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| 163 | * ) strip --strip-unneeded $i
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| 164 | ;;
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[85cd74c2] | 165 | esac
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| 166 | done</userinput><userinput arch="ml_x32,ml_all">
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[9282602] | 167 | for i in $(find /usr/libx32 -type f -name \*.so* ! -name \*dbg) \
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| 168 | $(find /usr/libx32 -type f -name \*.a); do
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[3330d51] | 169 | case "$online_usrbin $online_usrlib $save_usrlib" in
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[b8d5542] | 170 | *$(basename $i)* )
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| 171 | ;;
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| 172 | * ) strip --strip-unneeded $i
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| 173 | ;;
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[85cd74c2] | 174 | esac
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| 175 | done</userinput><userinput>
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[de28837] | 176 |
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| 177 | unset BIN LIB save_usrlib online_usrbin online_usrlib
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| 178 | </userinput></screen>
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[3c928f1] | 179 |
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[9c753b58] | 180 | <para>A large number of files will be flagged as errors because their file
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| 181 | format is not recognized. These warnings can be safely ignored. They
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| 182 | indicate that those files are scripts, not binaries.</para>
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[6c8a79a] | 183 |
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[3c928f1] | 184 | </sect1>
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