In this post we will explain how you can create your own Debian rootfs with pre-installed packages of your choice, which to allow tiny Linux images to be created.
All steps below should work on any Debian host (Debian/Ubuntu etc) and are verified with Ubuntu 12.04LTS.
First of all you need to install the support packages on your pc
sudo apt-get install qemu-user-static debootstrap binfmt-support
Next you need to choose the version of Debian in this case we are building a wheezy image.
Now we will build first stage of Debian rootfs :
sudo debootstrap --arch=armhf --foreign $distro $targetdir
Next copy the qemu-arm-static binary into the right place for the binfmt packages to find it and copy in resolv.conf from the host.
sudo cp /usr/bin/qemu-arm-static $targetdir/usr/bin/
sudo cp /etc/resolv.conf $targetdir/etc
If everything is right we now have a minimal Debian Rootfs
sudo chroot $targetdir
Inside the chroot we need to set up the environment again
Now we are setup the second stage of debootstrap needs to run install the packages downloaded earlier
Once the package installation has finished, setup some support files and apt configuration.
cat <<EOT > /etc/apt/sources.list
deb http://ftp.uk.debian.org/debian $distro main contrib non-free
deb-src http://ftp.uk.debian.org/debian $distro main contrib non-free
deb http://ftp.uk.debian.org/debian $distro-updates main contrib non-free
deb-src http://ftp.uk.debian.org/debian $distro-updates main contrib non-free
deb http://security.debian.org/debian-security $distro/updates main contrib non-free
deb-src http://security.debian.org/debian-security $distro/updates main contrib non-free
cat <<EOT > /etc/apt/apt.conf.d/71-no-recommends
Update Debian package database:
set up locales dpkg scripts tend to complain otherwise, note in jessie you will also need to install the dialog package as well.
apt-get install locales dialog
Install some useful packages inside the chroot
apt-get install openssh-server ntpdate
Set a root password so you can login
Build a basic network interface file so that the board will DHCP on eth0
echo <<EOT >> /etc/network/interfaces
iface eth0 inet static
Note: Your board will be accessible over SSH on IP address defined above !
Set the hostname
echo nameme > /etc/hostname
Enable the serial console, Debian sysvinit way
echo T0:2345:respawn:/sbin/getty -L ttyS0 115200 vt100 >> /etc/inittab
We are done inside the chroot, so quit the chroot shell
Tidy up the support files
sudo rm $targetdir/etc/resolv.conf
sudo rm $targetdir/usr/bin/qemu-arm-static
Now you have your Debian rootfs. Next step is to build Kernel, Uboot and to make your SD-card as explained in our early posts and Build instructions but instead to use the rootfs in the posts you can use your own minimal rootfs which you created above. The rootfs image created above is approx 150MB, it could be made smaller if you remove more packages.
Special thanks to Dimitar Gamishev (aka HEHOPMAJIEH) for creating this tutorial.