Make Ubuntu server 20.04 boot from an SSD on Raspberry Pi 4

6 min readAug 14, 2020

It has been a while since I’m interested in Raspberry Pi, the reason why I’ve 6 Raspberry Pi at home 😝; however, I prefer Ubuntu Server rather than Raspberry Pi OS (ex-Raspbian), and it’s totally a subjective opinion (I’m using Ubuntu since version 08.04. 12 years ago; I’m feeling too old!).

Say Goodbye to your SD-Card

Since last May 2020, Raspberry Pi Foundation has announced its big show “the arrival of USB boot on Raspberry Pi 4 in a beta version”, and since I’m holding this kind of Raspberry Pi, I was looking for how to make it possible with Ubuntu Server for RPi.

I’m using my 6 Raspberry Pi as a Kubernetes Cluster, and I have a lot of I/O operations, so using an SD-Card is not enough for me (an SSD Hard Disk is more suitable for I/O operations rather than an SD-Card). After a lot of googling, I didn’t find a complete way to make my Raspberry Pi 4 boot Ubuntu Server from USB (whether USB key or SSD external) [With 0 errors], that’s why I’ve decided to write this post to explain how to make it possible with easy steps, so I hope it will help you.

To achieve this operation we need:

Raspberry Pi 4b (at least 4 GBytes RAM).
SD-Card (at least 8 GBytes disk space).
USB key (or external SSD disk I’m using an SSD Disk with 256 GBytes space).
BalenaEtcher installed to flash the SD-Card and the SSD disk → https://www.balena.io/etcher/.
Raspberry Pi OS image → https://www.raspberrypi.org/downloads/raspberry-pi-os/ I’m using the lite version.
Ubuntu Server 20.04 64 bits for Raspberry Pi → https://ubuntu.com/download/raspberry-pi

Let’s dive into it

First, let me say that this procedure can be applied to any ARM OS and not just Ubuntu Server.

1- Burn the Raspberry OS on the SD-card using BalenaEtcher.

BalenaEtcher formats the SDCard with the Raspberry OS Image

2- Burn the Ubuntu Server on the SSD Disk using BalenaEtcher.

3- Boot your Raspberry Pi with the SD-Card (for the moment don’t plug the USB disk). If you want to access your Raspberry Pi from ssh, don’t forget to add the ‘ssh’ file to the boot partition.

add ssh file to enable ssh access to your raspberry pi

4- In my case, I’m accessing my Raspberry Pi via ssh (default username: pi and password: raspberry, don’t forget to change them after login 😛).192.168.0.4 is the address of my raspberry.

$ ssh pi@192.168.0.4

5- Now let’s upgrade the system:

$ sudo apt update && sudo apt full-upgrade -y

This operation will upgrade the system and all the installed applications.

6- Edit the rpi-eeprom-update file and replace firmware release status by ‘beta’ value:

$ sudo nano /etc/default/rpi-eeprom-update

7- Install the latest bootloader beta update by executing the next commands: (2020–07–31 is the date of the recent beta bootloader in my case).

# cd /lib/firmware/raspberrypi/bootloader/beta/
# rpi-eeprom-update -d -f pieeprom-2020-07-31.bin

Once the rpi-eeprom-update command finishes reboot the raspberry.

8- After rebooting, you can verify that the eeprom has been updated successfully by executing this command and verify that you have the last version:

$ vcgencmd bootloader_version

9- Now, plug the SSD disk to the Raspberry Pi and mount its partitions.

a- let’s find the name of the disk by executing

$ lsblk

/dev/sda1: the boot partition on the SSD.
/dev/sda2: the principal partition on the SSD.

b- let’s mount them on /mnt/boot (the boot partition) and /mnt/principal (the principal partition)

$ sudo mkdir /mnt/boot && sudo mount /dev/sda1 /mnt/boot
$ sudo mkdir /mnt/principal && sudo mount /dev/sda2 /mnt/principal

10- Now we’ll copy the content (*.dat & *.elf files) of /boot partition to /mnt/boot.

$ cd /mnt/boot
$ sudo cp /boot/*.elf /mnt/boot/ 
$ sudo sudo cp /boot/*.dat /mnt/boot/

11- let’s extract the vmlinuz file on the boot partition https://en.wikipedia.org/wiki/Vmlinux .

$ cd /mnt/boot
# zcat vmlinuz > vmlinux

12- Update the section [pi4] on config.txt file (located on /mnt/boot) as follow:

# nano /mnt/boot/config.txt

Add the next lines and save the file.

dtoverlay=vc4-fkms-v3d 
boot_delay 
kernel=vmlinux 
initramfs initrd.img followkernel

13- Now we’ll add a script for auto decompression of the Kernel in boot partition (/mnt/boot/) let’s name it auto_decompress_kernel.

#!/bin/bash -e# auto_decompress_kernel script#Set Variables 
BTPATH=/boot/firmware 
CKPATH=$BTPATH/vmlinuz 
DKPATH=$BTPATH/vmlinux  #Check if compression needs to be done. 
if [ -e $BTPATH/check.md5 ]; then  
   if md5sum --status --ignore-missing -c $BTPATH/check.md5; then
      echo -e "\e[32mFiles have not changed, Decompression not needed\e[0m"  
      exit 0  
   else 
      echo -e "\e[31mHash failed, kernel will be compressed\e[0m"  
   fi 
fi#Backup the old decompressed kernel 
mv $DKPATH $DKPATH.bak  
if [ ! $? == 0 ]; then  
   echo -e "\e[31mDECOMPRESSED KERNEL BACKUP FAILED!\e[0m"  
   exit 1 
else  
   echo -e "\e[32mDecompressed kernel backup was successful\e[0m" 
fi  #Decompress the new kernel 
echo "Decompressing kernel: "$CKPATH".............."  zcat $CKPATH > $DKPATH  if [ ! $? == 0 ]; then  
   echo -e "\e[31mKERNEL FAILED TO DECOMPRESS!\e[0m"  
   exit 1 
else  
   echo -e "\e[32mKernel Decompressed Succesfully\e[0m" 
fi  #Hash the new kernel for checking 
md5sum $CKPATH $DKPATH > $BTPATH/check.md5  if [ ! $? == 0 ]; then  
   echo -e "\e[31mMD5 GENERATION FAILED!\e[0m"  
else 
   echo -e "\e[32mMD5 generated Succesfully\e[0m" 
fi  #Exit 
exit 0

make it executable:

# chmod +x auto_decompress_kernel

14- Now, we’ll add a script 999_decompress_rpi_kernel in /mnt/principal/etc/apt/apt.conf.d/ folder to decompress the rpi kernel , it’s content is:

DPkg::Post-Invoke {"/bin/bash /boot/firmware/auto_decompress_kernel"; };

make it executable:

# chmod +x /mnt/principal/etc/apt/apt.conf.d/999_decompress_rpi_kernel

Here is a link for further reading https://debian-handbook.info/browse/wheezy/sect.apt-get.html#sidebar.directory.d

15- At this step, our journey is over, switch off the Raspberry Pi and unplug the SD-Card, switch it on then and enjoy booting from SSD disk. I’ll access my Raspberry Pi now via ssh but with ubuntu this time (default user and password are ubuntu/ubuntu).