Single board computer projects


Single board home server with Debian, openHAB 2 and MQTT

last updated: 19/06/20

My beaglebone was for some years a faithful server for my home data (photo-voltaic, heat-pump ...).

With more and more python scripts it had his problems and I got some times out of memory errors from the kernel. As I couldn't find the real cause of the errors (gnuplot very slow with big data files and many instances of gnuplot running at the same time?), I decided get another server for generating graphics.

In the meantime I got an Udoo X86 from a kickstarter campaign, and I will try to configure it as home server using MQTT and openHAB 2.

The Udoo advanced is a fan-less bard with an Intel Curie (x86 no arm) processor and 4GB RAM and a SATA port. Its much faster than the beaglebone or Raspi.

Naturally a Raspi can also be used with the newest Raspi OS (also Debian) to act as a home server. If a Raspi is used, some steps can be skipped.

Make a bootable USB-Stick from an .iso-file

The operating system will be debian stretch (this will also work for other distributions). Download the .iso file for net install (in my case: debian-9.3.0-amd64-netinst.iso).

To burn an .iso-file to a USB drive, you can use UNetbootin. UNetbootin allows to create bootable Live USB drives for Debian, Ubuntu, and other Linux distributions without burning a CD. It runs on Windows, Linux, and Mac OS X. You can either let UNetbootin download one of the many distributions or supply your own Linux .iso-file. The user interface is easy to use. Install in Linux with:

    sudo apt install unetbootin

In Linux you can also use the dd-command on the command line. Insert the USB drive (do not mount the drive), open a terminal and type dmesg. Now you see the name of your your drive (e.g. sdb, sde, ... ).

Now type the following command to burn the .iso-file:

    sudo dd status=progress if=debian-9.3.0-amd64-netinst.iso of=/dev/sde bs=4M

To test the burning, we can use QEMU, a machine emulator and virtualizer to boot into the usb drive. Install qemu (apt-get install qemu) and run the following command:

    sudo qemu-system-x86_64 -hda /dev/sde


Connect the external SSD

The power header of my SSD adapter has just two pins (5V and GND) in 2.54mm raster. Udoos header is 2mm raster with 4 pins (NC, 2 GND and 5V). A little hack was quickly done:

Udoo<em>SSD</em>circuit    Udoo_SSD

Connect a mouse, keyboard and HDMI display to Udoo to proceed. Udoo needs a 12V, 1A power supply (5-6W).

Install the operating system

Without a Stick Udoo boots in a boot shell. The Bios is configured to boot from USB, so power it up with the USB Stick inserted. If you need to change things in Bios, press ESC at boot.

After booting from the USB-Stick, choose the graphical install. Choose the right language, localization, configure your keyboard and enter a hostname (e.g udoo-server) and a domain name. If you leave the root password empty, debian will disable root and the normal user account will be given the power to be root with sudo.

After this create your user account.

I do the partitioning manually (Partition disks: Manual), and want to use the efi mode. All files are stored on the external SSD.

nr size device mount point file system partition
1 200 MB /dev/sda1 /boot/efi esp efi system partition
2 16 GB /dev/sda2 - swap swap partition
3 128 GB /dev/sda3 / ext4 root partition
4 106 GB /dev/sda4 /home ext4 home partition

After choosing a download server the installer asks for choose the software to install. As a server, I don't need a GUI, so I install debian headless only with an SSH server.

Update and upgrade

After reboot we log in and get the latest versions of all programs:

    sudo apt update
    sudo apt upgrade
    sudo apt dist-upgrade

It is a good idea to install the terminal file manager "midnight commander" (mc) to search and edit files as root in terminal (sudo mc), and htop an interactive process viewer.

    sudo apt install mc  htop

Set timezone

    sudo timedatectl set-timezone Europe/Luxembourg

Control with date. (to list all timezones : sudo timedatectl list-timezones)

Add sudo

If you have a root account and want to use sudo for your default user:

    apt install sudo
    addgroup username sudo

Static IP address

The IP address of your server is given with DHCP. To get it use the following command:

    ip a

To get a static IP adress is easy in Stretch. Use the editor nano or mc (F4) to append the following to the file /etc/network/interfaces.

# The primary network interface
allow-hotplug enp2s0
iface enp2s0 inet static

Save with CTRL+O and exit with CTRL+X and reboot.

Create a backup

After all this work we want to create a backup of the installation. To do so we use a Live USB Stick (e.g. Ubuntu) and boot the server from the Stick (ESC at reboot, Boot Manager).

We connect an external USB-HDD with more space then our SSD, open it in a filemanager (mounting) and locate the mount point (e.g. /media/ubuntu/label). After this we use dd to get an image. A pipe through gzip reduces the size.

    dd bs=1M if=/dev/sda | gzip > /media/ubuntu/bu/udooServerDeb.img.gz

Log in with SSH

Now we can remove the display, keyboard and mouse an login from another computer with SSH:

    sudo ssh username@

or as root:

    sudo ssh root@

If we don't know the IP address of the server after a reboot, because it was given by DHCP we can use the nmap-command. If nmap is not installed (for Windows look at ):

    sudo apt install nmap
    sudo nmap -sP 192.168.1.*

Look for the IP address of your server (e.g. and log in with SSH (putty on windows):

    sudo ssh username@

Install openHAB 2 on Linux

More infos in

OpenHAB 2 is written in Java, so we need a JAVA platform (For ARM sb-computers install the 32 bit version!).

As suggested we use Zulu:

    sudo apt install dirmngr
    sudo apt install software-properties-common python-software-properties
    sudo apt-key adv --keyserver hkp:// --recv-keys 0x219BD9C9
    sudo apt-add-repository 'deb stable main'
    sudo apt update
    sudo apt install zulu-8

Now we will install openHAB 2 stable release:

    wget -qO - '' | sudo apt-key add -
    sudo apt-get install apt-transport-https
    echo 'deb stable main'\
    | sudo tee /etc/apt/sources.list.d/openhab2.list
    sudo apt update
    sudo apt install openhab2

The backslash in line 3 means that the command from line 3 continues in line 4. If you type the command in one line, remove the backslash.

Now we can start openHAB 2 by and test if its running:

    sudo systemctl start openhab2.service
    sudo systemctl status openhab2.service

To start on installation, execute the following commands to configure openHAB 2 to start automatically using systemd:

    sudo systemctl daemon-reload
    sudo systemctl enable openhab2.service

Upgrade openHAB 2:

    sudo apt update
    sudo apt upgrade

Command Line interface (CLI) to use in terminal:

    openhab-cli backup [--full] [filename]   -- Stores the current configuration of openHAB.
    openhab-cli clean-cache                  -- Cleans the openHAB temporary folders.
    openhab-cli console                      -- Opens the openHAB console.
    openhab-cli info                         -- Displays distribution information.
    openhab-cli reset-ownership              -- Gives openHAB control of its own directories.
    openhab-cli restore filename             -- Restores the openHAB configuration from a backup.
    openhab-cli showlogs                     -- Displays the log messages of openHAB.
    openhab-cli start [--debug]              -- Starts openHAB in the terminal.
    openhab-cli status                       -- Checks status (openHAB running?)
    openhab-cli stop                         -- Stops any running instance of openHAB.

Using the openHab 2 karaf console

We can connect via ssh:

ssh -p 8081 -l openhab localhost

The default username is openhab, the password habopen. The most useful command is help. It lists all the other commands. When finished you get out with logout.

Example to view all active add-ons using MQTT:

bundle:list |grep -i MQTT

To view the log in real-time:


Paths for openHAB 2 files

In /etc/default we find the config file openhab2. In this file we find the links to the openHAB 2 default paths:


Install mosquitto

Install the mqtt server with:

    sudo apt install mosquitto

Using openHAB with MQTT devices

For more information read the tutorial about openHAB: Best is to use Visual Studio Code with openHAB plugin and a Samba share to edit the configuration files.

Here I will show how to set up openHAB for MQTT devices, using config files. The example device is an MVHR (mecanical ventilation with heat recuperation) system called piventi).

OpenHAB 2 defines the following base components:

Bindings: the numerous add-ons to communicate with your devices
Things: your physical devices represented in openHAB 2
Items: properties and capabilities linked to Channels of your Things
Groups: collections or categories containing Items
Sitemaps: user-defined front-end interfaces to arrange Groups, Items, ...
Transformations: helper functions to transform your data
Persistence: services to store data over time
Rules automation logic, the “smart” in your Smart Home!

The first step is to install the MQTT Binding to be able to communicate with MQTT devices. Than we add the Things (this is done in the *.things configuration file). The first Thing also called Bridge will be the MQTT server. The second Thing is our device. The device has different Channels (e.g. inflow temperature, exhaust humidity etc.) corresponding to the different MQTT messages sent over one ore more topics. As we use JSON strings over MQTT, Transformations help to get the right value from the JSON string.

OpenHAB works with Items in Rules or Sitemaps, so we must link all channels to Items (this is done in the *.items configuration file). After this we are ready to create a Sitemap to look at Items values or to sent values to the Items. Rules will help to automatize the devices reactions.

To show graphs we need a database to memorize values over time. This is done with Persistence. We will use InfluxDB for this service. And finally Grafana will be used to create the graphics.

If something hangs during the configuration you can restart openHAB with:

    sudo systemctl restart openhab2.service

Set up the MQTT Binding for openHAB 2

First we open openHAB in a browser with the url: serverip:8080 (e.g Then we select Paper UI to install the MQTT binding. Search in Add-ons > Bindings for MQTT Binding and install it (mid 2018 the old MQTT openHAB 1.x binding got obsolete; uninstall that binding!).

More infos can be found at: When configuring openHAB, always watch /var/log/openhab2/openhab.log for information.

(OpenHAB 2 now comes with an embedded MQTT broker if you don't want to use an external broker (Configuration > Things > + > Mqtt Binding > ADD MANUALLY > System MQTT Broker).)

Defining the Things

We need a configuration text file for our Generic MQTT device in /etc/openhab2/things/. Let's look at a some lines of a file to understand the syntax:

Config file Things
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For the MQTT server (Bridge) we need to provide a name (here udooserver) and optionally a Label and a Location ("Udooserver" @ "weigu"). The IP address is naturally important.

The same is true for our Thing (name piventi, label and location optional).

For the Channels we distinguish between data (stateTopic) and outgoing commands (commandTopic). First we need to provide the Type (here a number for incoming data and a string for outgoing JSON string commands). Important is the Channel name. The Label (between quotes) is optional. The topic is evidently important and it is a good practice to provide min and max values for the data. As the incoming data comes as a JSON string, a Transformation helps to get the value.

E.g. The inflow The MVHR is now sending MQTT messages in JSON format:


We can retrieve the temperature with "JSONPATH:$".

As all MQTT things use the same server, they have to be declared in the same things file, so best name it myMQTT.things :)!

Save your Things configuration file (e.g. piventi.things to the directory /etc/openhab2/things/.

Defining the Items

The syntax for Items is defined as follows:

itemtype itemname "labeltext [stateformat]" <iconname> (group1, group2, ...)
["tag1", "tag2", ...] {bindingconfig}

Fields must be entered in the order shown, itemtype and itemname are mandatory and all other fields are optional. Fields may be separated by one or more spaces, or tabs and an Item definition may span multiple lines.

Config file Items
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The labeltext with the stateformat and the iconname are helpful for the sitemap and should be added. It is also important to add the right stateformat! If you get e.g. a float number and don't specify the %f you don't see a number in PaperUI Configuration or your Sitemap!

The most important field is the link to a Channel. An easy way to get the right string is to look in PaperUI after configuring the Things file (Configuration > Things + click on Thing). We find even an icon to copy the name.

Config file Items get channel name

Save your Items configuration file (e.g. piventi.items to the directory /etc/openhab2/things/.

Testing in PaperUI Control

Go to PaperUI and click on Control. Under your location name you should be able to see the items and even sent messages.

PaperUI control

Defining the Sitemap

We create a text file with a content similar to the following text and name it e.g. piventi.sitemap. It is the saved in the sitemaps directory /etc/openhab2/sitemaps/. As the label and the icon are already defined in the Items configuration file, we don't need to do it here.

Sitemap configuration file
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BasicUI Sitemap

Defining the Rules

In an home automation system we want to automate things, so we need rules to do so. In openHAB the rules are defined in the .rules files. These files use a Domain Specific Language (DSL) near to Xtend, a general-purpose high-level programming language for the Java Virtual Machine. So if you want to dig deeper it is a goof idea to look here.

Let's look at a simple instruction line. Every rule begins with the keyword rule and has a minimum of one condition (when) and one or more instructions if the condition is fulfilled (then).

    rule "<RULE_NAME>"

Triggering a rule can mainly be:

Rules using items are only fulfilled if an event (change of a state) occurs.

In the when block we use a trigger condition. Item based trigger conditions use the following syntax:

    Item <item> received command [<command>]
    Item <item> received update [<state>]
    Item <item> changed [from <state>] [to <state>]

The then block includes a script to perform things we need. The language used is the same that is used in the Xtend language.

In the following example file we see a time based program for the ventilation (send flow-rate in %, JSON format). The list has half hour values for one day. in the time-based when block we have a cron time block, triggering every half an hour (Time cron"0 0/30 * * * ?").

In the then block we calculate the index for the list from the current time and get the corresponding value and convert it to a string. After this we cook the JSON string and send the command.

It is a good practice to send debug messages to the console to see if everything works as expected. We can use different log levels (WARN, ERROR, INFO,DEBUG, ...). Here the WARN level was chosen to get another colour in the log.

Config file Rules
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Create graphs in openHAB with InfluxDB and Grafana


To draw graphs, we need the possibility to store item states over time. This is called Persistence. As I want to use the complete data later for documentation a round-robin database like rrd4j is not a good idea. So I will use a time series database named InfluxDB.


Installation and starting the InfluxDB server

Look on for the latest version and install instructions.

First we install the package:

    mkdir ~/downloads
    cd ~/downloads
    sudo dpkg -i influxdb_1.8.0_amd64.deb  

Then we set environment variables (control with printenv):

    export INFLUXDB_CONFIG_PATH="/etc/influxdb/influxdb.conf"

The directories under /var/lib/influxdb are owned by root instead of InfluxDB, so we have to change this:

    cd /var/lib
    sudo chown -R influxdb:influxdb influxdb

To start the InfluxDB server:

    sudo systemctl start influxdb

Control if everything's alright (quit with q):

    sudo systemctl status influxdb
Create a Data Source

Before openHab can start persisting data in InfluxDB we have to create a database for openHAB.

Type influx to access to the InfluxDB shell:

Paste the following lines to create the InfluxDB database. Memorise your own passwords!:

    CREATE DATABASE openhab_db
    CREATE USER "openhab" WITH PASSWORD 'Password2'
    CREATE USER "grafana" WITH PASSWORD 'Password3'
    GRANT ALL ON "openhab_db" TO "openhab"
    GRANT READ ON "openhab_db" TO "grafana"

In /etc/influxdb/influxdb.conf we change and uncomment the following lines, to gain more security and to avoid statistical data:

    reporting-disabled = true
      dir = "/var/lib/influxdb/meta"
      dir = "/var/lib/influxdb/data"
      wal-dir = "/var/lib/influxdb/wal"
      enabled = true
      bind-address = ":8086"
      auth-enabled = true

Restart the server:

    sudo systemctl restart influxdb

To access the shell we need now to provide the password:

    influx -username 'admin' -password '***'
Installing the openHAB Persistence for InfluxDB

To connect the running database with openHAB we need a Persistence. Click on the Paper UI icon to install the InfluxDB Persistence. Choose in Add-ons Persistence the InfluxDB (v 1.0) Persistence and install it.

Edit the file influxdb.cfg (/etc/openhab2/services/) by changing the following lines (remove the #-sign!):


Add a file with the name influxdb.persit to (/etc/openhab2/persistence/) with the following content to save all changes of all Items in the database:

    Strategies {
           default = everyChange 
    Items {
           * : strategy = everyChange

Now the service InfluxDB is running, and an openHAB database was created. The user openhab has write access to the database and openHAB will save every value at every change in the database.

If there are problems, we can have a look in the log with:

    sudo journalctl -u influxdb.service


Grafana is a powerful tool to create graphics. We will only scratch the surface :).

Installation and starting the Grafana

We will download and install the latest version for Debian with:

    sudo apt install -y adduser libfontconfig1
    sudo dpkg -i grafana_7.0.3_amd64.deb

Look at for the latest version.

Check if the service is running:

    sudo systemctl status grafana-server.service

Make the service permanent:

    sudo systemctl enable grafana-server.service

Now let's change some configurations in /etc/grafana/grafana.ini. The semicolons ; have to be removed for a line to be active.

We will turn server reporting off, and don't want to sign up in our home network, so that we able as a Viewer to look at the dashboards.

Change the following lines:

    reporting_enabled = false
    allow_sign_up = false
    default_theme = light
    enabled = true

Restart the service with:

    sudo systemctl restart grafana-server.service

Now we can access the Grafana dashboard with with http://myip:3000 and the administration panel with http://myip:3000/login. User and password are admin. Change your password!

We must inform Grafana about which database we use. This is done in Configuration > Data Sources. Click on Add data source and choose InfluxDB.

We name the database openHAB InfluxDB. Add the IP in the URL and and choose With Credentials under Auth. In "InfluxDB Details" add the database and the user grafana.

Config grafana datasource
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Go to + and add a first dashboard. Click on the gear icon to change the name, and add tags. Don't forget to save.

Config grafana datasource
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Click on the "Add panel" icon and then on "+ Add new panel". Give the panel a title. Now we can add our Channels (Items) in the "FROM" field. For fill "previous" is a good choice to avoid gaps between the data points. We can customize our graph as needed, choosing lines or bars, the line thickness or colour, the axes text, the legend etc.. Don't forget to save.

Config grafana datasource
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After playing around a little bit, the dashboard could have the following aspect:

grafana dashboard
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We are also able to integrate Grafana dashboard graphics in our sitemap using a "Webview" object. With the code from=...&to=... we can adjust the time frame.

grafana in sitemap code
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And here the result:

grafana in sitemap
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Other things for our home server

Install paho-mqtt for python programs

    sudo apt install python3-pip
    sudo pip3 install paho-mqtt
    sudo apt install gnuplot

Install ssmtp for mailing

For mailing you have to install ssmtp (needed), mpack (for attachments) and berhaps mailutils (not mandatory):

    sudo apt install ssmtp mailutils mpack

With your editor you have to set up the defaults for SSMTP in /etc/ssmtp/ssmtp.conf. Edit the fields:


Test your mail with:

    echo "Hello world email body" | mail -s "Test Subject" my@mail.adr /usr/share/nano/openhab.nanorc

For troubleshooting:

Interesting links: