Nov 26, 2021

Raspberry PI on Ubuntu: yarn: Cannot find module 'worker_threads'

This evening i tried to install a nodejs application with yarn on my raspberry pi. This failed with:

/usr/local/bin/yarn install
    throw err;
Error: Cannot find module 'worker_threads'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:636:15)
    at Function.Module._load (internal/modules/cjs/loader.js:562:25)
    at Module.require (internal/modules/cjs/loader.js:692:17)
    at require (internal/modules/cjs/helpers.js:25:18)
    at /opt/zwavejs2mqtt/.yarn/releases/yarn-3.1.0-rc.8.cjs:287:2642
    at Object.<anonymous> (/opt/zwavejs2mqtt/.yarn/releases/yarn-3.1.0-rc.8.cjs:585:7786)
    at Module._compile (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
    at Module.load (internal/modules/cjs/loader.js:653:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:593:12)

This error occurs because the nodejs version which is delivered by ubuntu is version v.10.19.0.

You have to download the armv8 package from

With version v16.13.0 the error was gone...


Nov 20, 2021

AZ-900 achieved: Microsoft Azure Fundamentals

Yesterday evening i passed Microsofts AZ-900 exam:

Taking the exam on site was no option because of COVID-19, so tried the first time the online option. Nice thing: Many schedules and i chose 20:45. 

As examinee you have to start your online session half an hour earlier and this time you really need for the onboarding: 

  1. Download the software to your PC and do some checks (audio, network, ...)
    This is an .exe - so only windows PCs are possible
  2. Install the app "Pearson VUE" on your smartphone to provide
    1. selfie
    2. passport/driver license/...
    3. photos of your room
  3. Talking to an instructor
    You are not allowed to wear a headset - even a watch is not allowed

 After that the exam is about 40 questions in 45 minutes - quite fair.

 The questions are about these topics:

  • Describe cloud concepts (20-25%)
  • Describe core Azure services (15-20%)
  • Describe core solutions and management tools on Azure (10-15%)
  • Describe general security and network security features (10-15%)
  • Describe identity, governance, privacy, and compliance features (15-20%)
  • Describe Azure cost management and Service Level Agreements (10-15%)

More information can be found here:

If you want to do this exam, start here:

Nov 6, 2021

Fritz!Box monitoring with grafana, influx, collectd and fritzcollectd

 A nice way to monitor your Fritz!Box is this here:

How can you achieve this:


Here a list of the software packages you have to install

apt install -y collectd python3-pip libxml2 libxml2-dev libxslt1-dev influxdb nodejs git make g++ gcc npm net-tools certbot mosquitto mosquitto-clients grafana-server

for grafana-server and influxdb you have to add new repositories, because they are still not included in ubuntu.

To tell collectd, that it shoud write to influxdb, you have to uncomment the following in collectd.conf:

<Plugin network>
        Server "localhost" "25826"

and in influxdb.conf:

  enabled = true
  bind-address = "localhost:25826"
  database = "collectd"
  retention-policy = ""
  typesdb = "/usr/share/collectd/types.db"
  parse-multivalue-plugin = "split"

and of course inside collectd.conf you have to add the fritzcollectd config from the github link above.

But with starting collectd you might get the error:

dlopen("/usr/lib/collectd/") failed: /usr/lib/collectd/ undefined symbol: PyFloat_Type

This can be solved with adding into /etc/default/collectd:


Zigbee: Setup zigbee2mqtt with usbstick conbee II & influxdb on a raspberry pi

Just a short walkthrough of all steps which are necessary:

1.) insert the usbstick and check if this special device is there: /dev/ttyACM0 

if this device is not showing up, it might be, that your kernel does not support usbserial. In my case i had to downgrade from ubuntu server 21.10 to 21.04.

2.) follow these steps:


apt-get install -y nodejs git make g++ gcc npm
git clone /opt/zigbee2mqtt
cd /opt/zigbee2mqtt
npm ci

if you get 

prebuild-install WARN install EACCES: permission denied, access '/root/.npm/_cacache'

then you should not use root for running this command.

cd /opt/zigbee2mqtt
chown -R ubuntu node_modules
rm node_modules/*
npm ci

3.) install mqtt 

apt install mosquitto mosquitto-clients

4.) add to /etc/mosquitto/mosqitto.conf the line

listener 1883

and restart mosquitto (systemctl restart mosquitto)


5.) then start the zigbee2mqtt:

cd /opt/zigbee2mqtt
npm start

 if you get

Zigbee2MQTT:error 2021-11-06 09:05:23: Error: Error while opening serialport 'Error: Error: No such device or address, cannot open /dev/ttyACM0' 

then you did not really check step 1.): please check that /dev/ttyACM0 is missing - if yes: for me the kernel module (to list: lsmod) usbserial was missing. It seems, that ubuntu missed that on 21.10 - so i reinstalled 21.04....

if you get

zigbee2MQTT:error 2021-11-06 14:54:11: MQTT failed to connect: connect ECONNREFUSED

 then you did not get mosquitto running. Check with systemctl status mosquitto and follow step 3 and 4.

6.) configure telegraf, so that the data from mosquitto is transferred to influxdb. So you have to add to telegraf.conf:


   servers = ["tcp://"]
   topics = [
   data_format = "json"

   urls = ["unix:///var/run/influxdb/influxdb.sock"]
   username = "admin"
   password = "XXXXX"

7.) add this user to influxdb:


influx -ssl -unsafeSsl (only influx if you have not enabled SSL)

create user admin with password 'XXXXXXX' with all privileges

8.) if you have joined a device this the zigbee2mqtt, then you have to give a friendy name inside /opt/zigbee2mqtt/data/configuration.yaml

   friendly_name: 'sensor/t1'