Failed to start docker.service: Unit is masked

Problem

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

Solution

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:

https://forums.docker.com/t/failed-to-start-docker-service-unit-is-masked/67413

and from that the following bug post:

https://bugs.launchpad.net/ubuntu/+source/docker.io/+bug/1844894

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

Getting detailed information about your Linux distribution

To be able to get a more detailed information about your current linux distribution, including the code names use the following:

SSL: error:0B080074:x509 certificate routines:X509_check_private_key:key values mismatch

Problem

Trying to configure and use an nginx server that uses intermediate certifcates, you get the error about values mismatch and nginx does not start

Solution

It seems that this is a common mistake and it is mentioned here: https://nginx.org/en/docs/http/configuring_https_servers.html. In order to fix this you will need to change/reverse the original order that you have concatenated the chain, as in:

Decode access secret key from Terraform IAM user creation

Problem

You want to use the pgp encryption when using Terraform to create an AWS IAM user, and you have the secret access token returned as an output but encoded.

Solution

Use the following to get the actual secret key decoded (after copying your encoded key to a file encrypted_key.txt:

Raspberry, Ubuntu and Megatools

To install megtools (command line utilities for Mega.nz), in your raspberry with ubuntu installed follow the steps below (thanks to the instructions from here: https://www.instructables.com/id/Descarga-archivos-de-Mega-con-Raspberry-Pi/)

  • Install the necessary packages

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

  • Get the latest source code from https://megatools.megous.com
  • Compile and install them
  • Add your Mega account credentials in ~/.megarc like:
  • use the mega tools commands (megacopy, megals, megaget etc.

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):

https://ubuntu.com/tutorials/how-to-install-ubuntu-on-your-raspberry-pi#3-wifi-or-ethernet