Renaming multiple files in linux

Problem

You would like to rename multiple files, replacing some text with something else (like replacing Pixies_The with Pixies).

Solution

Install the rename utility

and replace the text as follows

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:

Using strace for analyzing performance

There is a very nice example on the O’reilly ‘Linux Under The Hood’ training about using strace to compare performance of two commands that provide the same output but with different calls. The two different commands were: ls and echo *, that they both provide the listing of the current directory.

First using the strace with ls:

And using the same with echo *

So the difference in time is 0.00000 for the echo and 0.000601 for the ls.

Similarly the number of calls for the echo is 33, but ls is using 100.

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.

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 https://asdf-vm.com/#/core-manage-asdf-vm):

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

Reload/Source your bash file with

Install the erlang plugin

If you get the following warnings:

Install the missing packages:

Install latest erlang version:

Set it up globally (if you want):

Add elixir plugin:

Install latest elixir version (1.10.3):

Set it up globally:

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

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