Ubuntu Base Minimal Image (Xenial Xerus 16.04.3)

These are my annotations on how to build Ubuntu Xenial Base Minimal Image (barebone minimal image) for the Nano Pi M3 (HOWTO).

For this instructions we need a chroot environment and kernel 4.11.6 pre-built.
I have a ready kernel 4.11.6 built with GCC 7.1 but you can use any kernel or build your own.
These instructions works with Ubuntu Xenial (linux box) but can be adapted to any Distro and can be used with other boards if you have a Kernel ready.

When you use this instructions for different board, chose the Kernel and bootloader target to that board.

• Ubuntu Xenial 16.04 (Ubuntu Base)
• 62 MB of RAM in use
• No Desktop, just networking
• No debootstrap
• This instructions were created on Ubuntu Xenial 16.04 Box (64 bit)

For this we are going to use Ubuntu Base rootfs with some pre-built packages made by the Ubuntu Team.

System Requirements

• Ubuntu Xenial 16.04 (Host PC)
• Chroot environment, wget, git, qemu, etc…
• Kernel pre-built for your board
• SD CARD ( 2 GB will fit, but better use >= 8 GB )
• USB reader/writer (get a good one)

Important

• Get a good SD CARD brand and a good USB reader/writer or you will get the final SD CARD with bad data, don’t blame me*

Instructions

1. Download this instructions

git clone https://github.com/avafinger/nanopi-m3-ubuntu-base-minimal
cd nanopi-m3-ubuntu-base-minimal

or

Use [Clone or download] green button
uncompress
cd nanopi-m3-ubuntu-base-minimal-master

2. Set up your chroot environment

We need the chroot tools to access the ARM64 Ubuntu Base rootfs from the X86_64 (HOST PC) and add some packages

3. Get the Ubuntu Base files

wget http://cdimage.ubuntu.com/ubuntu-base/xenial/daily/current/xenial-base-arm64.tar.gz

4. Find your SD CARD

Insert the SD CARD into USB card reader/writer and check:

dmesg|tail
[  181.158588] sd 6:0:0:0: [sdc] 30547968 512-byte logical blocks: (15.6 GB/14.6 GiB)
[  181.159831] sd 6:0:0:0: [sdc] Write Protect is off
[  181.159835] sd 6:0:0:0: [sdc] Mode Sense: 03 00 00 00
[  181.160836] sd 6:0:0:0: [sdc] No Caching mode page found
[  181.160841] sd 6:0:0:0: [sdc] Assuming drive cache: write through
[  181.167092]  sdc: sdc1 sdc2
[  181.170832] sd 6:0:0:0: [sdc] Attached SCSI removable disk
[  182.194865] EXT4-fs (sdc1): mounted filesystem with ordered data mode. Opts: (null)
[  182.202709] EXT4-fs (sdc2): mounted filesystem without journal. Opts: (null)

The SD CARD is in the format /dev/sdX where X is a letter (b,c,….), in our case is c (from above)

sd card is /dev/sdc

5. Format SD CARD with specific geometry

sudo ./format_sd.sh /dev/sdc

6. Prepare the SD CARD with Ubuntu Base Minimal Rootfs

Change the SDCARD=/dev/sdX (our sd card device) to your /dev/sdX (X is your device letter)

sudo su
export SDCARD=/dev/sdc
mkdir -p rootfs
mount $SDCARD"2" rootfs

7. Decompress the rootfs

tar -xvpzf ./xenial-base-arm64.tar.gz -C ./rootfs --numeric-ow
sync

8. Prepare the SD CARD to chroot

cp /usr/bin/qemu-aarch64-static ./rootfs/usr/bin/
cp /usr/bin/qemu-arm-static ./rootfs/usr/bin/
sync

9. Prepare chroot to add some needed packages

cp -fv /etc/resolv.conf ./etc/resolv.conf
cp -rvf ./etc/* ./rootfs/etc
sync

10. Update our SD CARD with the pre-built kernel

mkdir -p ./rootfs/lib/modules
sudo tar -xvpzf kernel.tar.gz -C ./rootfs/lib/modules --numeric-ow
sync
mkdir -p ./rootfs/lib/firmware
sudo tar -xvpzf firmware.tar.gz -C ./rootfs/lib/firmware --numeric-ow
sync

Chroot to SD CARD and add networking

chroot ./rootfs /bin/bash
(*) apt-get install network-manager (add a ton of packages you may not need)
apt-get install kmod
apt-get install ifupdown
apt-get install net-tools
sync
exit (*Exit from chroot*)

11. Edit with your preferred editor the file ./rootfs/etc/passwd

Change the line from

root:x:0:0:root:/root:/bin/bash

to

root::0:0:root:/root:/bin/bash

and save

12. Unmount the partition

umount ./rootfs
sleep 1
rm -rf ./rootfs

13. Prepare the Boot

mkdir -p boot
mount $SDCARD"1" boot
sleep 1
sudo tar -xvpzf boot.tar.gz -C ./boot --numeric-ow
sync
sleep 1
umount ./boot
sleep 1
rm -rf ./boot

Prepare the booloader

sudo dd if=bl1.bin of=/dev/sdc seek=1
sync
sudo dd if=u-boot.bin of=/dev/sdc seek=64
sync

Exit from su (root)

exit

14. We have now our Ubuntu Base Minimal Image on SD CARD

Just make sure the SD CARD is unmounted and remove it from the USB reader/writer

You can boot the board with this new SD CARD, default to DHCP.
You will be asked the user: root (without the password)

15. If you read this, you have suceeded and from now on you should:

• apt-get update and apt-get dist-upgrade and add packages
• Add user, add sudoers, locales, timezone, keyboard layout, ssh, services, etc…. and restore the line we changed in the passwd file

Enjoy your Ubuntu Xenial Base Minimal Image!

Credits

• Special thanks to @rafaello7 for the Kernel 4.11.6