The solution that I was using for the problem causing Domoticz to shut down if there was time synchronization problem does not work in Ubuntu 18.04 (Bionic). The problem is discussed at length and a new solution using a systemd unit file to start the service is provided.

The first four sections of this post were previousl in the the guide to Home Automation Servers on Raspbian Buster Lite. To lighten that discussion, three of those sections have been removed from the guide and replaced with the last section presented here.

Table of Contents

1. Installing Domoticz
2. Time Syncrhonization Problem
3. Auto Restart Domoticz Service
4. Wait for systemd-timesync
5. Use a Unit File to Start Domoticz

Installing Domoticz

Installing Domoticz is as simple as always when following The "easy" way instructions.

The installation script will install the git and libudev-dev packages.

Start a browser and go to the address specified. The home automation system will display the following page.

This is a good place to express all my gratitude to the Domoticz development team as well as to the community.

Check that everything is functioning correctly. Something like the following should be displayed.

If an error about a missing Python library appears,

then install the python3-dev package.

Time Problem with Domoticz

Everything looks to be in order but this may not the case. Power down the Raspberry Pi, wait six minutes or more and then turn the power on making sure that the device has access to the Internet. Try to open the Domoticz web page. It may be that the web server cannot be reached because the domoticz.service started and then mysteriously stopped.

Even if you do not have this known problem, please read on because it could present itself later on.

Note the 6-minute gap between the last two entries in the log. As waaren explains in a Domoticz Forum entry Crashes on cold start on Raspberry and other systems without RTC, the server "interprets this time [gap] as a hang of some critical internal processes" and shuts down. The Domoticz server will work after a reboot or after restarting the service manually, which is not an acceptable solution.

As waaren says, I should not have encountered the problem because there was a real-time clock (RTC) (DS3231, see part 3 of this series of posts) on the Raspberry Pi. Fortunately, its battery was dead so it was not doing anything. I changed the RTC battery and the service no longer crashes on cold starts. Clearly, this could be a recurring problem when the battery expires again, so the Domoticz installation needs to be improved to handle the situation when the RTC is no longer functioning.

On the older Raspberry Pi there will not be a real-time clock. So I tried using the startupdelay option when starting Domoticz, by editing the start up script.

I added a 30 second delay to the DAEMON_ARGS parameter.

The result was disappointing.

Clearly the time had not been updated when the script was started but after the 30 second delay when domoticz was starting up the time was correct. Nevertheless, the service was stopped.

In his forum post, waaren suggests ways of working around the problem. The most elegant may very well be Alexandre Gambier's Domoticz restart service which is discussed next. I devised a different solution based on the built-in smtp client systemd-timesync. It works well in Raspbian Buster but it does not work in Ubuntu Bionic (18.04) or Armbian images based on Ubuntu. Starting Domoticz with a systemd unit file has proven to be a generally valid solution. If impatient, click on this link Use Unit File to Start Domoticz to go directly to what is now my preferred solution, jumping over the discussion of the other solutions.

Auto Restart Domoticz Service

Installing the service is a simple affair: create a directory and then add a short unit file in that directory.

Copy the content of Alexandre Gambier's unit file:

[Service]
Type=forking
PIDFile=/run/domoticz.pid
RemainAfterExit=no
Restart=on-failure
RestartSec=5s

into the text editor and then exit nano (CtrlX), saving the file when prompted. Reload all unit files and check that the restart configuration service has been installed.

Check by powering down the Pi.

Wait at least six minutes and then power up and look at the logs.

That works very well, the service was stopped as before but then the restart service kicked in and Domoticz was restarted and remained running.

As promised, the drop-in restart service did not restart Domoticz this time because it was not stopped. The only niggling problem is a warning shown in the service status report or when stop or restarting the service.

To get rid of the restart drop-in service, just delete the domoticz.service.d directory in /etc/systemd/system and reload the service unit files.

Wait for systemd-timesync

I decided to use another approach based on the one proposed by waaren. It's interest for me lies in the fact that it works with the Raspberry Pi 3 with a working or non-working RTC and with the Raspberry Pi 1 which does not have an RTC and where ntp will not be installed. All that is required is a few extra lines in the Domoticz start script.

Insert a while loop at the beginning of the do_start() function. It will wait until systemd-timesync has created a file named synchronized to indicate that it has obtained a valid date and time. If systemd-timesync, an sntp client, has not synchronized with a server within n seconds, the do_start() will be exited returning a value of 2 meaning the daemon could not be started. I take no credit for this, I just adapted the script by jcyr found on his reply in the Raspberry Forum. There are other approaches that could be of interest in that discussion. The following shows the the change in action when an ssh session was opened just after the Raspberry Pi without a hardware real time clock was rebooted.

The status of the domoticz.service was checked just after booting and as can be seen, the install script was still waiting for systemd-timesync. The second time around, the sntp client had finally got the time from an Internet time server after about 20 seconds. If the Domoticz service were to be restarted, it would be "Sync'd" right away.

Here is the unformatted while loop to add to the start script.

Use Unit File to Start Domoticz

The modifications to the domoticz.sh script proposed above will not work in Ubuntu 18.04 (Bionic) which is the distribution on my desktop. I have encountered the same problem with a version of Armbian based on Ubuntu 18.04 (Bionic). Even though Ubuntu 18.04 is based on Debian Buster, it uses an older version of systemd with a systemd-timesync that does not create the /run/systemd/timesync/synchronized file.

It is easy enough to ascertain the version of systemd.

So at some time between version 237 found on Ubuntu 18.04 and version 241 found on Rasbian Buster, systemd-timesync started creating the syncrhonized file.

It is possible to avoid the crash problem by starting Domoticz with an systemd unit file with appropriate parameters instead of the init script. Indeed the Linux page on the Domoticz Wiki recommends using the appropriated method for starting a service on Linux distributions with systemd as the init program.

The first step is to create the unit file with nano or an editor of choice.

Here is an example unit file. The condition After=time-sync.target will ensure that the service is installed only once the system time has been synchronized. The parameter AmbientCapabilities=CAP_NET_BIND_SERVICE is needed if a TCP port less than 1024 is specified which is the case below where port 443 will be used for secured HTTP connections. See the Wiki page for more details, especially if an older version of Raspbian is being used.

Of course, the user name woopi needs to be adjusted and note that it appears 3 times in the unit file.

Now stop Domoticz if it is running and remove the script (saving it in case something goes wrong). Reload daemons, start the Domoticz service and check its status to ensure everything is correct.

The following command will instruct systemd to automatically start the service at boot time.

This command, which creates a symbolic link to the newly created Domoticz unit file, needs to be launched only once.

When booting up after power has been off for more than 10 minutes or so, do not worry if initially the Domoticz service does not appear to be functioning:

It will be restarted in about one minute by which time the time-sync.target will have been reached and the service will be running.

Hopefully that is the end of this saga.