Low disk space hint

jsmaby at virgo.umeche.maine.edu jsmaby at virgo.umeche.maine.edu
Sat Sep 28 07:10:11 PDT 2002


TITLE:		LFS for small hard drives
LFS VERSION:	4.0
AUTHOR:		James Smaby <jsmaby at virgo.umeche.maine.edu>

SYNOPSIS:
	The recommended LFS partition size is 1GB.  By following
	this hint, that number can be 300MB, and possibly lower.
	So if you're on a 486, or want to compile LFS in RAM,
	this hint is for you.

HINT:
    Much more space is needed to build LFS than is needed for the
final system.  There used to be a general rule that once you're past
glibc, you're all set, but now gcc-3 is a similarly high hurdle.
Note that gcc-2.95.3-2, used in LFS-3.3, is smaller, and in some
people's opinions, better than gcc-3, and using it might be a good
idea for people low on disk space.  You'll need about 300MB of disk
space available to LFS, less if you use gcc-2 and don't install
the locales.  The disk space doesn't all have to be physical.  You can
stick some things on a tmpfs if you have spare RAM, or just really
need the space.  Indeed, you can build an LFS entirely in RAM if
you have more than about 350MB, using:
  mount tmpfs -t tmpfs -o size=300m $LFS
You can also save quite a bit of space if the sources for glibc
and glibc are already unpacked and on a cdrom.

    First off, the default compiler options of "-O2 -g" make large
binaries/object files.  Assuming you won't need debugging information
in the system's executables/libraries, the following environment
variables should be set (these are conservative; -march=i686 will
help, but might break glibc/gcc/binutils).
  export CC="gcc -s"
  export CFLAGS="-Os -fomit-frame-pointer -s"
  export BOOT_CFLAGS="$CFLAGS"

     For chapter 5, build gcc-3 first, as it's the biggest package.
Depending on available space, you may want to delete some of the
unused sources first:
  rm -rf libjava libobjc gcc/ada gcc/f gcc/java gcc/objc
Using make bootstrap uses extra space, and if you have a trustworthy
compiler on your host, bootstrap is unneeded.

     After completing chapter 5, make a minimal static by running
these commands:
  mkdir -p $LFS/minimal/bin
  mkdir -p `echo $LFS/static/lib/gcc-lib/*/*/include | sed s/static/minimal/`
  # Copy over only the files used by building a chapter 6.
  # These were found using find -anewer
  cp -a $LFS/static/bin/{ar,as,awk,basename,bash,bzip2,cat,cc,chmod,\
    chown,cmp,cp,cpp,cut,date,diff,dirname,du,echo,egrep,env,expr,fgrep,\
    find,fold,gawk,gcc,grep,gunzip,gzip,head,hostname,install,install-info,\
    ld,ln,ls,make,makeinfo,mkdir,mknod,mount,mv,nl,nm,objdump,od,pwd,\
    ranlib,readelf,rm,rmdir,sed,sleep,sort,strip,tail,tar,touch,tr,true,\
    uname,uniq,wc,whoami,xargs,zcat} $LFS/minimal/bin
  cp -a $LFS/static/lib/gcc-lib/*/*/{cc1,collect2,cpp0,crtbegin.o,crtbeginS.o,\
    crtbeginT.o,crtend.o,crtendS.o,libgcc.a,specs} $LFS/minimal/lib/*/*/*
  cp -a $LFS/static/lib/gcc-lib/*/*/include/{float.h,limits.h,stdarg.h,
    stdbool.h,stddef.h,stdio.h,syslimits.h} $LFS/minimal/lib/*/*/*/include
  # Strip any unneeded symbols from binaries
  strip $LFS/minimal/bin/* $LFS/minimal/lib/*/*/*/{cc1,collect2,cpp0}
  # Strip debugging symbols from object files
  strip -g $LFS/minimal/lib/*/*/*/*.*
  # Use bash builtins for some commands
  echo -e '#!/bin/bash\n echo $@' > $LFS/minimal/bin/echo
  echo -e '#!/bin/bash\n pwd' > $LFS/minimal/bin/pwd
  echo -e '#!/bin/bash\n sleep $@' > $LFS/minimal/bin/sleep
  echo -e '#!/bin/bash\n' > $LFS/minimal/bin/true
  echo -e '#!/bin/bash\n echo root' > $LFS/minimal/bin/whoami
If all goes well, "du -sh $LFS/minimal" should produce 35M.  That's all
you need of a chapter 5 to build a chapter 6.  Replace the old static:
  rm -rf $LFS/static
  mv $LFS/minimal $LFS/static

After entering chroot, you lose your environment variables.  Reset
them here:
  export CC="gcc -s"
  export CFLAGS="-Os -fomit-frame-pointer -s"
  export CXXFLAGS="$CFLAGS"
  export BOOT_CFLAGS="$CFLAGS"

On to the first hurdle, glibc.  Really the only thing you can do
that I've found is add "--enable-omitfp --enable-kernel=2.4.19" to
the configure line.  After it's built, you should be getting awfully
close to 300MB.  Relieve a little stress by killing libc_g.a:
  echo -n > libc_g.a
We don't care about debugging, so this (25MB!) file isn't needed.
Now "make install" should have room.  Run the following commands
to free up even more:
  strip /{usr/,}{lib/*so,sbin/*,bin/*}
  strip -g /usr/lib/*.a
  rm /usr/lib/*_g.a
  bzip2 /usr/share/info/*info*
If you really, _really_ need them, you can install the locales, but
they eat up precious space.

    Okay, onto gcc.  If you're using gcc-2, then you're fine, and can
just go on to do the rest of the LFS.  We'll need some tweaking for gcc-3.
Note that installing man-pages is preferably done after gcc to save
about 6MB for the gcc build.  First, delete some of the bigger unneeded
source directories:
  rm -rf libjava libobjc gcc/ada gcc/f gcc/java gcc/objc
There won't be enough room (to stay under 300MB) to do a bootstrap compile,
so just type "make".  This has the advantage that it takes quite a bit
less time to compile :-)  You may need to do some preliminary stripping
before installing:
  strip gcc/{cc1,cc1plus}
  find . -name *.so -exec strip {} \;

    Things may start getting a little tight when building perl; compressing
the man and info pages should be enough to make room:
  bzip2 -d /usr/share/info/*.bz2
  bzip2 /usr/share/info/*info*
  bzip2 /usr/share/man/man?/*.?

    Now you can get busy stripping down your fresh LFS to make room for
more programs/data.

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