Systemd on Ubuntu 16.04 gives no such interface error

Question

I'm now trying to deploy my Phoenix(Elixir) application in Ubuntu 16.04. For persistency, I'm using this file (app.service) in /lib/systemd/system.

[Unit]
Description=Runner for My Phoenix App

[Service]
WorkingDirectory=/app
Environment=MIX_ENV=prod PORT=4000
ExecStart=/app/bin/app start
ExecStop=/app/bin/app stop
User=mohideen
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

My username is mohideen and the account has sudo rights. When I try to use the command sudo systemctl start app.service, the command fails with the following error:

Failed to start app.service: Unknown unit: app.service
See system logs and 'systemctl status app.service' for details.

When I type sudo systemctl status app.service, I get this message:

Failed to get properties: No such interface ''

The app works fine when I start it manually. Why am I getting this error? How can I ensure that my application gets restarted on reboot and crash?

Answer 1

There were two reasons for my problem.

Firstly, my .service file location was wrong. It should be /etc and not /lib.

Secondly, upstart was installed earlier by me. This prevents .service files from running (I don't know why). Once I uninstalled upstart and re-installed systemd, the problem was solved!