Hardware

You will need 3 or 4Gb free on your hard drive. A fast CPU is recommended, especially if you run QEMU. To have an idea of emulation speed, lets consider the approximate execution time of the command dd if=/dev/zero bs=1M count=10 | gzip > /dev/null :

• native ARM920t@400MHz (Eten G500 based on s3c2440) : 4.8 seconds
• QEMU on a 1.1GHz Pentium-M : 7.8 seconds
• QEMU on a Intel Core Duo 6400 : 2.8 seconds (faster than native processor, looks interesting)
• x86 native code on a 1.1GHz Pentium-M : 0.4 second

64Mb of RAM is not enough, use 128Mb or add some swap space.

Software

The following list of required softwares is not exhaustive. It shows the major components involved in the build process.

• Linux kernel : http://www.kernel.org/, using 2.6.18.3, patched for QEMU/armv4t
• Cross Linux From Scratch book and packages : http://trac.cross-lfs.org/, using 1.0.0
• QEMU : http://fabrice.bellard.free.fr/qemu/, using 0.8.2, patched for armv4t
• Trip : http://www.pierrox.net/trip/, using 0.2
• Unionfs : http://www.am-utils.org/project-unionfs.html, using 1.4
• Network : you need TUN/TAP on the host in order to create a virtual network interface between virtual ARM machine and host. Additionnaly your computer must be configured to export the NFS share $CLFS_TRIP to the virtual machine. You may choose another configuration.

Of course you can deviate from the versions used here. In this case I cannot certify it will work of course. I cannot even certify that using the very same versions will lead to the same result, as many components take part in the process of building softwares.

Other

Internet, brain, books, time, eventually coffee.

Preparations

We choose /home/clfs-trip as root for our work. Create some directories :

export CLFS_TRIP=/home/clfs-trip
mkdir -p $CLFS_TRIP/{src,build,dist,root,pkg,vm}
        

Where the purpose of these directories are :

• src : store the source packages and patches
• build : temporary build directory
• dist : locally installed softwares
• root : location of CLFS files, the final root filesystem, the NFS root of the virtual machine
• pkg : temporary location used to "fake install" packages (see trip)
• vm : files used by the ARM virtual machine

Gather the required source files :

cd $CLFS_TRIP/src
wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.18.3.tar.bz2
wget ftp://ftp.fsl.cs.sunysb.edu/pub/unionfs/unionfs-1.4.tar.gz
wget http://belnet.dl.sourceforge.net/sourceforge/e2fsprogs/e2fsprogs-1.39.tar.gz
wget http://fabrice.bellard.free.fr/qemu/qemu-0.8.2.tar.gz
wget http://www.pierrox.net/G500/20070109/config-2.6.18.3-versatile_pb-920t
wget http://www.pierrox.net/G500/20070109/linux-2.6.18.3-versatile_pb-920t.patch
wget http://www.pierrox.net/G500/20070109/qemu-0.8.2-versatile_pb-920t.patch
wget http://www.pierrox.net/G500/20070109/trip-0.2-clfs-1.0.0.tar.gz
        

Furthermore download the CLFS book and needed packages and patches as described in CLFS chapter 3.2 and 3.4. In case some external dependencies are unreachable, they are mirrored at http://www.pierrox.net/G500/20070109/.

Build CLFS /cross-tools and /tools

Follow the CLFS-1.0.0 book from chapter 1 to end of 6. There is no ARM specific guide but following MIPS (and replacing mips with arm) is ok. Take care when following the book not to include MIPS specific parts (patches and asm headers for example).
At the end of chapter 6, /tools and /cross-tools are ready to build the basic system software. I choosed as CLFS_TARGET arm-9tdmi-linux-gnu.

Important : make sure these variables are set :

CLFS_TRIP=/home/clfs-trip
CLFS=$CLFS_TRIP/root
CLFS_HOST="$(echo $MACHTYPE | sed "s/$(echo $MACHTYPE | cut -d- -f2)/cross/")"
CLFS_TARGET=arm-9tdmi-linux-gnu
PATH=/cross-tools/bin:$PATH
export CLFS_TRIP CLFS CLFS_HOST CLFS_TARGET PATH
        

Create some essentiel directories, device nodes and symlinks

mkdir -p $CLFS/{dev,proc,sys,bin,tmp}
mkdir -p $CLFS/usr/lib
mkdir $CLFS/dev/{pts,shm}
mknod -m 600 $CLFS/dev/console c 5 1
mknod -m 666 $CLFS/dev/null c 1 3
ln -sv /tools/bin/{bash,cat,grep,pwd,stty} $CLFS/bin
ln -sv /tools/lib/libgcc_s.so{,.1} $CLFS/usr/lib
ln -sv /tools/lib/libstd* $CLFS/usr/lib
ln -sv bash $CLFS/bin/sh
mkdir -p $CLFS/mnt/{pkg,union}
        

Install Trip

Untar the trip-0.2-clfs-1.0.0.tar.gz, it contains both trip-0.2 and the clfs-1.0.0 associated trip packages.

cd $CLFS
tar xf $CLFS_TRIP/src/trip-0.2-clfs-1.0.0.tar.gz
mv trip-0.2-clfs-1.0.0 trip
        

Create a temporary fstab for trip pkg and unionfs filesystems

mkdir $CLFS/etc
echo << EOF > $CLFS/etc/fstab
192.168.101.2:/home/clfs-trip/pkg      /mnt/pkg     nfs      defaults,nolock            0    0
unionfs                                /mnt/union   unionfs  dirs=/mnt/pkg:/=ro         0    0
EOF
        

Build an ARM Linux kernel

This kernel will be used for the QEMU virtual machine. The provided linux config file mainly configures the kernel with ARM versatile PB machine type and support for NFS root.

cd $CLFS_TRIP/build
tar xjf $CLFS_TRIP/src/linux-2.6.18.3.tar.bz2
cd linux-2.6.18.3
cp $CLFS_TRIP/src/config-2.6.18.3-versatile_pb-920t .config
patch -p1 < $CLFS_TRIP/src/linux-2.6.18.3-versatile_pb-920t.patch
make ARCH=arm CROSS_COMPILE=arm-9tdmi-linux-gnu-
make ARCH=arm CROSS_COMPILE=arm-9tdmi-linux-gnu- INSTALL_MOD_PATH=/tools modules_install
cp arch/arm/boot/zImage $CLFS_TRIP/vm/kernel-2.6.18.3
        

The patch applied on the kernel tree allows to choose a 920t processor for the versatile pb machine.

Build the unionfs module

Unionfs is required for Trip.

cd $TRIP_CLFS/build
tar xzf $CLFS_TRIP/src/unionfs-1.4.tar.gz
cd unionfs-1.4
make LINUXSRC=$CLFS_TRIP/build/linux-2.6.18.3 \
     CC=arm-9tdmi-linux-gnu-gcc \
     ARCH=arm \
     CROSS_COMPILE=arm-9tdmi-linux-gnu- \
     unionfs.ko
make LINUXSRC=$CLFS_TRIP/build/linux-2.6.18.3 \
     CC=arm-9tdmi-linux-gnu-gcc \
     ARCH=arm \
     CROSS_COMPILE=arm-9tdmi-linux-gnu- \
     MODPREFIX=$CLFS/tools \
     MODDIR=lib/modules/2.6.18.3 \
     install-mod
        

Build QEMU

cd $CLFS_TRIP/build
tar xf $CLFS_TRIP/src/qemu-0.8.2.tar.gz
cd qemu-0.8.2
patch -p1 < $TRIP_CLFS/src/qemu-0.8.2-versatile_pb-920t.patch
./configure --prefix=/usr/local/qemu \
            --cc=/usr/local/gcc-3.4.6/bin/gcc \
            --host-cc=/usr/local/gcc-3.4.6/bin/gcc \
            --target-list=arm-user,arm-softmmu
make install
        

Some explanations :

• --prefix=/usr/local/qemu : choose your prefix as you like, but since it is a patched version, avoid /usr
• --cc=/usr/local/gcc-3.4.6/bin/gcc : qemu has problems with gcc4, you may have to install an older gcc version, use this option according to your own build environment
• --target-list=arm-user,arm-softmmu : this selects only the ARM emulation

Configuring and starting QEMU

QEMU has a lot of options, so putting the command line in a script is probably a good idea.

cd $CLFS_TRIP/vm
cat << EOF > qemu.sh
/usr/local/qemu/bin/qemu-system-arm \
    -M versatilepb_920 \
    -kernel kernel-2.6.18.3 \
    -nographic \
    -append "root=/dev/nfs rw nfsroot=192.168.101.2:/home/clfs-trip/root \
             ip=192.168.101.3::192.168.101.2:255.255.255.0:bipbip:eth0:off \
             console=ttyAMA0 \
             init=/tools/bin/bash" \
    -net nic -net tap,script=./qemu-ifup.sh
EOF
chmod +x qemu.sh
        

Some explanations :

• -M versatilepb_920 : select the type of emulated arm system, in our case it is our special version of versatile pb based on 920t
• -kernel kernel-2.6.18.3 : being able to boot directly the kernel avoid us to install a boot loader and a more complex system
• -nographic : disables the video output. For the moment it will not be used but will be reactivated later
• -append "..." : this selects the command line passed to the kernel (see bellow)
• -net nic -net tap,script=./qemu-ifup.sh : this select the virtual network interface mode

The kernel command line is composed of these parameters :

• root=/dev/nfs rw nfsroot=192.168.101.2:/home/clfs-trip/root : tells the kernel to use the prepared root filesystem as its root
• ip=192.168.101.3::192.168.101.2:255.255.255.0:bipbip:eth0:off : configure the ethernet interface with a fixed ipv4 adress
• console=ttyAMA0 : the first UART is used as the QEMU console, so that typing in the terminal will send characters to the VM console

The qemu-ifup.sh script configures the tap interface :

cat << EOF > qemu-ifup.sh
#!/bin/sh

ifconfig tap0 192.168.101.2
EOF
chmod +x qemu-ifup.sh
        

So we use 192.168.101.2 for the host and 192.168.101.3 for the guest. Instead of a tap interface you may prefer to use bridging.

Booting this way drops the user in a really restricted environment. However this is enough for what we have to do and it avoids to install more packages.

./qemu.sh
        

From that point all steps take place in the virtual machine console

Build some additionnal packages

As our "init" is just a bash, we need to dome some work manually when the virtual machine is started.

export PATH=/bin:/usr/bin:/sbin:/usr/sbin:/tools/bin:/trip/trip/bin
        

Set the date manually because this virtual machine has no RTC clock.

date -s "<enter the current date !>"
        

Build additionnal tools that will be used later :

cd /trip/tmp
tar xf /trip/clfs-1.0.0/src/util-linux-2.12r/src/util-linux-2.12r.tar.bz2
cd util-linux-2.12r
patch -p1 -i  ../util-linux-2.12r-gcc4_fixes-1.patch
cp -v configure{,.orig}
sed -e 's@/usr/include@/tools/include@g' configure.orig > configure
./configure
make ARCH="" CPU="" -C lib
make ARCH="" CPU="" -C mount mount umount
make ARCH="" CPU="" -C text-utils more
cp -v mount/{,u}mount text-utils/more /tools/bin
          

cd /trip/tmp
tar xf /trip/clfs-1.0.0/src/module-init-tools-3.2.2/src/module-init-tools-3.2.2.tar.bz2
cd module-init-tools-3.2.2
./configure --prefix=/tools
make
make install
          

cd /trip/tmp
tar xf /trip/clfs-1.0.0/src/perl-5.8.8/src/perl-5.8.8.tar.bz2
cd perl-5.8.8/
./configure.gnu --prefix=/tools    -Dstatic_ext='Data/Dumper IO Fcntl POSIX' -Dcc="gcc"
make perl utilities
cp -v perl pod/pod2man /tools/bin
install -dv /tools/lib/perl5/5.8.8
cp -Rv lib/* /tools/lib/perl5/5.8.8
ln -sv /tools/bin/perl /usr/bin
          

Build packages using trip

Now everything is setup to build final packages. The following command will load the unionfs module and mount the pkg NFS share, as required for trip :

insmod /tools/lib/modules/2.6.18.3/kernel/fs/unionfs/unionfs.ko
mount /mnt/pkg
        

Each package should be built using : trip -b /trip/clfs-1.0.0/src/<package>. Once the package has been built a binary package is created and can be installed with trip -i <binary package>. For example : trip -b /trip/clfs-1.0.0/glibc-2.4 && trip -i glibc-2.4-1.armv4t.tar.gz.

Build the packages in this order :

• clfs-base-1.0.0
• linux-headers-2.6.17.13-09092006
• man-pages-2.34
• glibc-2.4

Adjusting the toolchain : this operation does not fit in any package, so do it once. In case you would like to come back to the previous step, in order to re-use the /tools directory for another build, just remove the file $(dirname $(gcc --print-libgcc-file-name))/specs.

gcc -dumpspecs | \
perl -p -e 's@/tools/lib/ld@/lib/ld@g;' \
     -e 's@\*startfile_prefix_spec:\n@$_/usr/lib/ @g;' > \
          $(dirname $(gcc --print-libgcc-file-name))/specs
        

Continue with these packages :

• binutils-2.17
• gcc-4.1.1 : you will get normal conflicts on previously created symlinks, install with trip --no-conflict -i gcc-4.1.1-1.armv4tl.tar.gz
• coreutils-5.96 (conflicts with previously created symlinks, use --no-conflict)
• iana-etc-2.10
• m4-1.4.4
• bison-2.3
• ncurses-5.5
• procps-3.2.6
• sed-4.1.5
• libtool-1.5.22
• flex-2.5.33
• iproute2-2.6.16-060323
• perl-5.8.8 (conflicts with previously created symlinks, use --no-conflict)
• readline-5.1
• zlib-1.2.3
• autoconf-2.59
• automake-1.9.6
• bash-3.1 (conflicts with previously created symlinks, use --no-conflict)
• bzip2-1.0.3
• diffutils-2.8.7
• e2fsprogs-1.39
• file-4.17
• findutils-4.2.27
• gawk-3.1.5
• gettext-0.14.5
• grep-2.5.1a (conflicts with previously created symlinks, use --no-conflict)
• groff-1.19.2
• inetutils-1.4.2
• gzip-1.3.5
• kbd-1.12
• less-394
• make-3.81
• man-1.6d
• mktemp-1.5
• module-init-tools-3.2.2
• patch-2.5.9
• psmisc-22.2
• shadow-4.0.16
• sysklogd-1.4.1
• sysvinit-2.86
• tar-1.15.1
• texinfo-4.8
• udev-096
• util-linux-2.12r
• vim-7.0
• clfs-bootscripts-1.0.0
• udev-rules-1.0.3
• clfs-configuration-1.0.0

Post build configuration

Update the root password since it has not yet a correct value

passwd root
        

Note : at this stage it seems the qemu keyboard handling makes passwd fail. If you encounter the same problem, use passwd -d root and choose another password later.

Create the final fstab :

echo << EOF > $CLFS/etc/fstab
192.168.101.2:/home/clfs-trip/root   /            nfs     defaults              0     0
proc                                 /proc        proc    defaults              0     0
sysfs                                /sys         sysfs   defaults              0     0
devpts                               /dev/pts     devpts  gid=4,mode=620        0     0
shm                                  /dev/shm     tmpfs   defaults              0     0

192.168.101.2:/home/clfs-trip/pkg    /mnt/pkg     nfs     defaults,nolock       0     0
unionfs                              /mnt/union   unionfs dirs=/mnt/pkg:/=ro    0     0
EOF
        

Create a .bashrc and .bash_profile for the root user (examples) :

cat << EOF > /root/.bashrc
#!/bin/bash

alias cp='cp -i'
alias rm='rm -i'
alias mv='mv -i'
alias ll='ls -l --color'

[ "\s-\v\$ " = "\s-\v\$ " ] && PS1="[\u@\h \W]\$ "
EOF

cat << EOF > /root/.bash_profile
#!/bin/bash

LC_ALL=POSIX
PKG_CONFIG_PATH=/usr/lib/pkgconfig
PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/X11R6/bin:/trip/trip/bin

export LC_ALL PKG_CONFIG_PATH PATH

if [ -f ~/.bashrc ]
then
  source ~/.bashrc
fi
EOF

        

Indicates the known shells (will be used later by dropbear for example) :

cat << EOF > /etc/shells
/bin/bash
EOF
        

At last but not least, modify inittab so that a getty is started on our console (ttyAMA0, first virtual UART), so that we can login after the next reboot.

sed 's/tty1 9600/ttyAMA0 115200/' -i /etc/inittab