RaspberryPi for monitoring screens

November 29, 2015

Monitoring TV screens

Displaying dashboard screens on a TV is a very common case, especially in IT companies. TVs in the offices display business dashboards or the status of the applications or infrastructure. Although there are multiple options to do it, we are mostly using RaspberryPi 2 to display Kibana, Grafana, Zabbix or other screens.

RaspberryPi 1 is too weak to display Kibana screens properly, therefore we had tried other alternatives as well. Google Chromecast devices, which are easy to use and cheaper than Raspberries, were dropping connections periodically, so they were unsuitable for the day-to-day use. Other options, like MiniPC’s are really good, but they are much more expensive.

RaspberryPi 2 is much more powerful than its predecessor and can handle “heavier” dashboards. They are pretty reliable, yet quite cheap, therefore we stuck to these devices.

However it needs to be configured properly in order to satisfy the following needs:

What you need

Be aware that NOT all the SD cards are compatible with RaspberryPi. Refer to the compatibility list for the list of compatible/incompatible SD cards.

RaspberryPi

Download OS for the RaspberryPi

The RaspberryPi comes with no operating system and with no internal storage. Therefore it is necessary to download the Operating system and install it to the microSD card. The officially supported OS is Debian-based Raspbian, although there are 3rd party OS images available as well.

Although there is an “easy” installation method “Noobs”, I prefer downloading regular Raspbian image and copy it to the SD card.

For this tutorial I was using Raspbian Wheezy. There might be some nuances with the newer versions of Raspbian. Please share your feedback if you are using Jessie or newer versions of Raspbian.

Copy image to the SD card

Burning an SD card from image using Windows can be done with the Win32 disk imager application.

From Linux the dd utility is used. Firstly it is necessary to unmount all partitions from the SD card (if they are mounted). The next step is copying the image to the SD card using the following command:

$ sudo dd if=/path/to/raspbian/image of=/dev/mmcblk0 bs=4M

The dd command parameters are these:

See also: Raspbian installation guide

Plugging-in

After the SD card is prepared, it is needed just to plug it in, connect power and Ethernet cables and plug the HDMI cable to RaspberryPi and the TV set. The RaspberryPi will boot to the command line.

Configure Raspberry

Firstly, perform the basic configuration actions by launching the raspi-config utility as a root user:

$ sudo raspi-config

Expanding filesystem to the SD card size

In order to use the full capacity of the SD card, it is necessary to expand the filesystem:

Expanding Raspbian filesystem

Booting to the GUI instead of command line

Booting Raspbian to GUI

Booting Raspbian to GUI

Disabling overscan

In order to fill the TV screen fully with the view, it might be necessary to disable Overscan:

Booting Raspbian to GUI

Booting Raspbian to GUI

Booting Raspbian to GUI

Connecting via SSH

All this and further configuration can be done by connecting to the RaspberryPi from the remote computer via SSH:

$ ssh pi@<raspberry IP address>

The default user is pi, the password is raspberry.

The one thing that needs to be known is the IP address to connect to. This information can be obtained using ifconfig command (run from RaspberyPi command line).

Changing password

Due to security reasons it is wise not to use the default password for RaspberryPI, as it is a normal computer inside your network.

The password can be changed with passwd command.

Also I recommend to use SSH keys when connecting to RaspberryPI via SSH.

Changing time zone

By default RaspberryPI should operate in UTC time. It can be useful to set the timezone according to specific location. It can be done using command dpkg-reconfigure tzdata.

Updating system

Run the following commands to update the system:

sudo apt-get update
sudo apt-get upgrade

Installing applications

The following applications will be used:

It is possible to install them from a repository using the following commands:

$ sudo apt-get install chromium-browser iceweasel unclutter xscreensaver xautomation

Configuring unclutter

It is necessary to setup unclutter to run automatically by writing the following text to the file ~/.config/autostart/unclutter.desktop

[Desktop Entry]
Version=1.0
Type=Application
Name=unclutter
Exec=unclutter -idle 1 -root
Terminal=false
StartupNotify=false

Configuring xscreensaver

To disable the screensaver (the screen becoming blank when after the inactivity period) it is necessary to create a file ~/.xscreensaver with the content:

mode: off

Configuring chromium

2016-03-23 note: the latest version of Chromium in the repository is 22. For some web applications (i.e. Kibana 4) this version is too old. Consider using other up-to-date web browser (i.e. Firefox) or build Chromium from source or use alternate repository.

Running chromium

Chromium is run by executing the ~/run_chromium.sh script. The only thing that needs to be changed is the URL that has to be opened.

Create ~/run_chromium.sh with content:

#!/bin/bash
rm -rf ~/.chromium_temp_dir
DISPLAY=:0 chromium-browser --kiosk --incognito --disable-translate --user-data-dir=.chromium_temp_dir http://example.com

It uses the custom user directory in order to prevent unclean shutdown errors. The --incognito flag should be enough, but if the user profile directory gets corrupted, this is the easiest way to bypass any errors.

--kiosk will run browser in the “Kiosk” (full-screen with some other restrictions) mode.

--disable-translate will not suggest to translate the websites.

Restarting chromium

In case it is necessary to restart Chromium (i.e. if it gets stuck or the dashboard URL needs to be changed), the ~/restart_chromium.sh script can be run. It works well when being connected via SSH, so there is no need to plug the keyboard or mouse to the RaspberryPi to restart it.

Create ~/restart_chromium.sh with content:

#/bin/sh

killall chromium-browser
~/run_chromium.sh > /dev/null 2>&1 &

Making chromium auto-run

Create ~/.config/autostart/chromium.desktop with the content:

[Desktop Entry]
Version=1.0
Type=Application
Name=chromium-browser
Exec=~/run_chromium.sh
Terminal=false
StartupNotify=false

Iceweasel - an alternative to Chromium

As stated previously, Chromium build is very old in the repository. To use Kibana4 and other modern web applications, the recent web browser is needed.

The good alternative can be the Firefox fork Iceweasel.

The configuration is identical to the one described in the previous section, despite the content of run_chromium.sh should be the following

#!/bin/bash

iceweasel "http://www.example.com" --display=:0 &
sleep 15s;
xte "key F11" -x:0

Cloning SD card

After the single SD card is configured, it might be useful to clone it to run multiple instances of Chromium on multiple TVs. It can be done using the same dd command.

Create an image from the SD card:

$ sudo dd if=/dev/mmcblk0 of=~/sdcard.img bs=4M

Clone the image to the card:

$ sudo dd if=~/sdcard.img of=/dev/mmcblk0 bs=4M

Credits and further reading

Big thanks to Julius Vitkauskas for aggregating the best ideas.

You can also read blog posts from alexba.in or danpurdy.co.uk.