This section is optional. If the intended user is not a programmer and does not plan to do any debugging of the system software, the system's size can be decreased by some 2 GB by removing the debugging symbols, and some unnecessary symbol table entries, from binaries and libraries. This causes no real inconvenience for a typical Linux user.
Most people who use the commands mentioned below do not experience any difficulties. However, it is easy to make a mistake and render the new system unusable. So before running the strip commands, it is a good idea to make a backup of the LFS system in its current state.
A strip command with
the --strip-unneeded
option
removes all debug symbols from a binary or library. It also removes
all symbol table entries not needed by the linker (for static
libraries) or dynamic linker (for dynamically linked binaries and
shared libraries).
The debugging symbols from selected libraries are compressed with Zlib and preserved in separate files. That debugging information is needed to run regression tests with valgrind or gdb later, in BLFS.
Note that strip 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 strip is
affected, the binary or library being stripped can be destroyed; this
can make the system completely unusable. To avoid this problem we
copy some libraries and binaries into /tmp
, strip them there, then reinstall them with
the install command.
(The related entry in Section 8.2.1, “Upgrade Issues”
gives the rationale for using the install command here.)
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 g
, in case the commands
below have already been run.
If there is any package whose version is different from the version
specified by the book (either following a security advisory or
satisfying personal preference), it may be necessary to update the
library file name in save_usrlib
or
online_usrlib
. Failing to do so may render the system completely
unusable.
save_usrlib="$(cd /usr/lib; ls ld-linux*[^g]) libc.so.6 libthread_db.so.1 libquadmath.so.0.0.0 libstdc++.so.6.0.33 libitm.so.1.0.0 libatomic.so.1.2.0" cd /usr/lib for LIB in $save_usrlib; do objcopy --only-keep-debug --compress-debug-sections=zlib $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-2.43.1.so libsframe.so.1.0.0 libhistory.so.8.2 libncursesw.so.6.5 libm.so.6 libreadline.so.8.2 libz.so.1.3.1 libzstd.so.1.5.6 $(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
A large number of files will be flagged as errors because their file format is not recognized. These warnings can be safely ignored. They indicate that those files are scripts, not binaries.