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In this repository you will find all the steps and extra files used to create the stretch image for the B3 platforms.

Given the fact that image creation is not done every day there is no scripted/automated method to create it ; instead all the steps needed (and taken) to create the released image will be described in this README. It will be updated with each release.

The current version for the excito stretch image is 1.0


  • This file, the "image create manual"
  • first-boot which contains first-boot scripts run ... on the first boot; Currently these scripts:
    • Generate new ssh host keys
    • Remove themselves

Image creation


In order to create an image you need a B3 running whatever standard Linux OS you wish, ~1GiB free space and an internet connection; The only software needed on the host is the debootstrap package.

The released image are created from the install/rescue system which provides all the necessary tools.

Everything must be run as root.

Boostraping and chroot into the system

  • Create a directory that will host the image (it doesn't have to be a mounted partition):
mkdir /mnt/target
  • Debootstrap stretch:
debootstrap --arch=armel stretch /mnt/target 
  • Mount the kernel filesystems:
mount -t proc none /mnt/target/proc
mount -t sysfs none /mnt/target/sys
mount -o bind /dev /mnt/target/dev
mount -t devpts none /mnt/target/dev/pts
mount -t tmpfs none /mnt/target/dev/shm
  • Create the policy-rc.d file which will prevent the daemons to be run inside the chroot:
cat > /mnt/target/usr/sbin/policy-rc.d << EOF
exit 101
chmod 755 /mnt/target/usr/sbin/policy-rc.d
  • Chroot into the system and setup the environment:
chroot /mnt/target /bin/bash
source /etc/profile
cd /root
export PS1="(chroot) $PS1"

APT configuration and standard package install

  • Create the /etc/mtab link:
ln -s /proc/mounts /etc/mtab
  • Add security repository to sources.list:
cat >> /etc/apt/sources.list << EOF
deb stretch/updates main
  • Download and install the excito-release-stretch package:
wget -q
dpkg -i excito-release-stretch.deb
rm excito-release-stretch.deb
  • Update apt cache and ugprade the system:
apt-get update
apt-get -y dist-upgrade
  • Install kernel and b3 utils:
apt-get -y install bubba3-kernel b3-utils
  • Install locales and standard system tools:
apt-get -y install locales
tasksel install --new-install standard ssh-server

[Optional] Install u-boot-tools to access u-boot configuration

Released images provide fw_setenv and fw_printenv which allows access and modification of the platform bootloader. These tools are only 'nice to have'. Beware that misuse can prevent the system from booting.

  • Create the fw_env.config file:
cat > /etc/fw_env.config << EOF
# MTD definition for Bubba|3
# MTD device name       Device offset   Env. size       Flash sector size       Number of sectors
/dev/mtd1		0x000000	0x010000	0x010000
  • Install the u-boot-tools and the mtd-utils package:
apt-get -y install u-boot-tools mtd-utils

User and password creation

  • Set the root password ('excito' without quotes on the released images):
  • Create the excito user and set its password ('excito' without quotes on the released images):
useradd -m -U -s /bin/bash excito
passwd excito

System configuration

  • Reconfigure the exim4 mail server with the following answers: dpkg-reconfigure exim4-config
    • General type of mail configuration: local delivery only; not on a network
    • System mail name: b3 for the B3
    • IP-addresses to listen: ; ::1
    • Other destinations: empty
    • Keep number of DNS-queries minimal: No
    • Delivery method for local mail: mbox format in /var/mail
    • Split configuration into small files: No
    • Root and postmaster mail recipient: excito
  • Configure the network:
cat >> /etc/network/interfaces << EOF

allow-hotplug eth0
iface eth0 inet dhcp

allow-hotplug eth1
iface eth1 inet dhcp
  • Create /etc/fstab:
cat > /etc/fstab << EOF
/dev/sda1   /   ext3    noatime 0   1
  • Set the hostname:
echo "b3" > /etc/hostname


  • Empty apt cache:
apt-get clean
  • Remove previously created ssh keys (they will be recreated by the first-boot files):
rm /etc/ssh/*key*
  • Exit the chroot:
  • Remove the shell history file and the previously created policy-rc.d file:
rm /mnt/target/usr/sbin/policy-rc.d /mnt/target/root/.bash_history
  • Unmount kernel filesystem:
umount /mnt/target/dev/shm
umount /mnt/target/dev/pts
umount /mnt/target/dev
umount /mnt/target/sys
umount /mnt/target/proc

first-boot files and tarball creation

  • Download and extract the first-boot release tarball into target:
wget -O/mnt/target/first-boot.txz
( cd /mnt/target; tar -xvf first-boot.txz )
rm /mnt/target/first-boot.txz
  • Now that the image files are ready, go ahead and create the final tarball:
( cd /mnt/target; tar -cJvf /root/stretch-image.txz .)


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