Failed to start docker.service: Unit is masked


Trying to start the docker service after some upgrades fails with the following message:

Failed to start docker.service: Unit is masked.


It turns out that after upgrading or more specifically removing and then upgrading the docker installation in ubuntu (in this particular case in raspberry 4 with Ubuntu 20.04 installed), results in this error.

A search brings up the following:

and from that the following bug post:

So the solution is to run the following to be able to start the docker service (described in the first link above):

sudo systemctl unmask docker
sudo systemctl start docker

Raspberry, Ubuntu and Megatools

To install megtools (command line utilities for, in your raspberry with ubuntu installed follow the steps below (thanks to the instructions from here:

  • Install the necessary packages
sudo apt-get -y install build-essential libglib2.0-dev libssl-dev libcurl4-openssl-dev libgirepository1.0-dev 

You may also need to add some additional packages if there is an error about the documentation.

  • Get the latest source code from
  • Compile and install them
tar xvfz megatools-1.10.3.tar.gz
cd megatools-1.10.3
sudo make install
sudo ldconfig
  • Add your Mega account credentials in ~/.megarc like:
Username = my_mega@email
Password = mypassword
  • use the mega tools commands (megacopy, megals, megaget etc.

Erlang and Elixir with asdf in Raspberry 4 with Ubuntu 20.04

To install the latest/current versions of erlang (23.0.2) and elixir (1.10.3), follow the instructions below:

Install asdf ( full instructions

git clone ~/.asdf --branch v0.7.8

Add the following two lines in your ~/.bashrc file:

# Add asdf version manager 
. $HOME/.asdf/
. $HOME/.asdf/completions/asdf.bash

Reload/Source your bash file with

source ~/.bashrc

Install the erlang plugin

asdf plugin add erlang

If you get the following warnings:

Extracting source code
Building Erlang/OTP 23.0.2 (asdf_23.0.2), please wait...
WARNING: It appears that a required development package 'libssl-dev' is not installed.
WARNING: It appears that a required development package 'automake' is not installed.
WARNING: It appears that a required development package 'autoconf' is not installed.
WARNING: It appears that a required development package 'libncurses5-dev' is not installed.
Configure failed.

Install the missing packages:

sudo apt install libssl-dev automake autoconf libncurses5-dev

Install latest erlang version:

asdf install erlang latest
Erlang/OTP 23.0.2 (asdf_23.0.2) has been successfully built

Set it up globally (if you want):

asdf global erlang 23.0.2

Add elixir plugin:

asdf plugin add elixir

Install latest elixir version (1.10.3):

asdf install elixir latest

Set it up globally:

asdf global elixir 1.10.3-otp-23

Finally you can also install the latest Phoenix version (1.5.3):

mix archive.install hex phx_new 1.5.3

WiFi, Raspberry Pi 4 B, Ubuntu 20.04

After installing an image of the Ubuntu server on the Raspberry 4, the wifi is not automatically configured after the initial book.

In order to be able to use the WiFi follow the steps described below for setting up your wifi in your SD card, and then reboot your raspberry (make sure that the indentation in the yaml file is correct, and also your WiFi access point is enclosed in quotes):