Steps to get ubuntu-system (use armhf as arch): https://help.ubuntu.com/lts/installation-guide/armhf/apds04.html

sudo apt-get install qemu-user-static debootstrap binfmt-support
 
distro=bionic
#distro=focal
arch=armhf
#for bpi-r64 use arch=arm64
targetdir=$(pwd)/debootstrap_ubuntu_${distro}_${arch}
 
 
sudo debootstrap --arch=$arch --foreign $distro $targetdir
 
#if you got this error: E: Cannot install into target '...' mounted with noexec or nodev
sudo mount -i -o remount,exec,dev /mounted_dir
 
sudo cp /usr/bin/qemu-arm-static $targetdir/usr/bin/
sudo cp /etc/resolv.conf $targetdir/etc
sudo distro=$distro chroot $targetdir
export LANG=C
/debootstrap/debootstrap --second-stage
 
#echo "deb-src http://archive.ubuntu.com/ubuntu $distro main">>/etc/apt/sources.list
#echo "deb http://security.ubuntu.com/ubuntu $distro-security main">>/etc/apt/sources.list
#echo "deb-src http://security.ubuntu.com/ubuntu $distro-security main">>/etc/apt/sources.list
echo "deb http://ports.ubuntu.com/ubuntu-ports/ $distro main">>/etc/apt/sources.list
echo "deb-src http://ports.ubuntu.com/ubuntu-ports/ $distro main">>/etc/apt/sources.list
echo "deb http://ports.ubuntu.com/ubuntu-ports/ $distro-updates main">>/etc/apt/sources.list
echo "deb-src http://ports.ubuntu.com/ubuntu-ports/ $distro-updates main">>/etc/apt/sources.list
echo "deb http://ports.ubuntu.com/ubuntu-ports/ $distro-security main">>/etc/apt/sources.list
echo "deb-src http://ports.ubuntu.com/ubuntu-ports/ $distro-security main">>/etc/apt/sources.list
 
echo "bpi-r2-ubuntu" >/etc/hostname 
#set root-password! else you will not be able to login
passwd

configure fstab/… like it's done for debian ubuntu 18.4 uses netplan as default network-framework bionic releasenotes

#exit chroot
exit

pack:

cd $targetdir
sudo tar cvpzf ../debootstrap_${distro}_${arch}.tar.gz .

prepare SD-Card

#unpacking in root-partiton with
sudo tar -xpzf /path/to/debootstrap_$distro.tar.gz
sudo mkdir lib/modules/
cd lib/modules/
#unpack kernel-modules here

temporary configure network:

ip a
ip link set eth0 up
ip addr add 192.168.0.11/24 dev lan0 #ip/prefix in your lan-segment not used
ip link set lan0 up
ip route add default via 192.168.0.10 #ip from your router
echo "nameserver 192.168.0.10" >>/etc/resolv.conf #ip from your router for dns resolution

install “ifupdown” and add “netcfg/do_not_use_netplan=true” to bootopts in /boot/bananapi/bpi-r2/linux/uEnv.txt

after reboot the “old” system with /etc/network/interfaces is used. currently /etc/resolv.conf is resetted every reboot

root@bpi-r2-ubuntu:~# ls -l /etc/resolv.conf                                    
lrwxrwxrwx 1 root root 39 Jun 13 10:27 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf
#delete symlink and replace it by a static file with your settings
rm /etc/resolv.conf
echo "nameserver 192.168.0.10" >>/etc/resolv.conf

in ubuntu 18.4 there is a own dns-service running, which have to be disabled (followed by a reboot or stop), in order to get e.g. DNSMasq running (like in my wifi.sh-script)

systemctl disable systemd-resolved
systemctl stop systemd-resolved

imgfile=/path/to/ubuntu-18.04-bpi-r2-preview.img
 
#create img file from sdcard (optional if no img file available)
sudo dd if=/dev/sdx of=$imgfile
#watch state of dd from another terminal with "sudo kill -SIGUSR1 $(pidof dd)"
 
#truncate image to last partitions end (mbr only,do not use for gpt)...make sure your path does not contain spaces!
IFS=$'\t' #just for security reasons (ignore spaces in path)
ENDOFDATA=$(fdisk -l "$imgfile" |tail -1|awk '{print $3}')
echo $ENDOFDATA
truncate --size=$[($ENDOFDATA+1)*512] $imgfile
#check size
ls -lh "$imgfile"
 
#maybe do some stuff with the img
loopdev=$(losetup -f)
sudo losetup $loopdev $imgfile
sudo partprobe $loopdev
sudo mount ${loopdev}p2 /mnt
ls /mnt
#overwrite free space with zeros for better packing and not leaving possible sensitive data 
sudo sh -c 'cat /dev/zero >/mnt/null.dat'
sudo rm /mnt/null.dat
sudo umount /mnt
 
#pack image
gzip $imgfile
md5sum $imgfile.gz > $imgfile.gz.md5

i have uploaded my image to my gdrive for testing (ubuntu-18.04-bpi-r2-preview.img.gz)

Lan0-IPv4 is 192.168.0.11 (second port,next to wan) you can change it in /etc/network/interfaces. More on network

Sdcard:

dd if=path/to/ubuntu.img of=/dev/sdx

Emmc:

• dd if=path/to/ubuntu.img of=/dev/mmcblkx
• maybe you need reboot reading the partitiontable
• First follow steps here
• in /boot/bananapi/bpi-r2/linux/uEnv.txt: find the line “root=…” and replace /dev/mmcblk0p2 with /dev/mmcblk1p2
• in /etc/fstab: replace /dev/mmcblk0p2 with /dev/mmcblk1p2

ssh-server is installed on my image ubuntu-18.04-bpi-r2-preview.img.gz from my gdrive, but root-login have to be enabled

echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
service sshd restart

you should create new host-keys for ssh…

#first delete your old keys
rm /etc/ssh/ssh_host_*
#reconfigure sshserver-package
dpkg-reconfigure openssh-server