I am running a Flask application on my RPi successfully by issuing the following command
export FLASK_APP=/opt/fzwk-access-source/app.py && flask run --host 0.0.0.0 Now, my next goal is naturally to run the Flask application when booting up the RPi. To do so, I created the service /etc/systemd/system/fzwk-access.service, which looks as follows:
[Unit] Description=fzwk-access After=network.target [Service] User=root Group=root Type=forking WorkingDirectory=/opt/fzwk-access-source ExecStart=/bin/bash -c "export FLASK_APP=/opt/fzwk-access-source/app.py && flask run --host 0.0.0.0" [Install] WantedBy=default.target ls -la provides me with the following:
... 4 drwxr-xr-x 2 root root 4096 Dec 2 12:41 dhcpcd.service.d 0 lrwxrwxrwx 1 root root 34 Dec 2 12:41 dhcpcd5.service -> /lib/systemd/system/dhcpcd.service 4 -rwxr-xr-x 1 root root 312 Mar 1 17:12 fzwk-access.service 4 drwxr-xr-x 2 root root 4096 Dec 2 12:37 getty.target.wants 4 drwxr-xr-x 2 root root 4096 Dec 2 12:39 [email protected] 4 drwxr-xr-x 2 root root 4096 Dec 2 12:40 halt.target.wants 4 drwxr-xr-x 2 root root 4096 Feb 18 07:38 multi-user.target.wants ... With that in place, I can start the service with the command
sudo systemctl start fzwk-access successfully. I have thus enabled the service with
sudo systemctl enable fzwk-access My expectation now is that after a reboot the service is starting successfully, but it does not.
sudo systemctl status fzwk-access shows the following:
● fzwk-access.service - fzwk-access Loaded: loaded (/etc/systemd/system/fzwk-access.service; enabled; vendor preset: enabled) Active: inactive (dead) Clearly, I am missing something here – I cannot figure out what it is...
Update
It turns out that running sudo systemctl start fzwk-access does not work as intended – it will start the Flask server temporarily, but will fail with a timeout (I did not realise that this was happening before because during that startup period of the server, Flask was answering my requests perfectly...). Anyway, it fails with
fzwk-access.service - fzwk-access Loaded: loaded (/etc/systemd/system/fzwk-access.service; enabled; vendor preset: enabled) Active: failed (Result: timeout) since Mon 2021-03-01 18:58:43 GMT; 4min 36s ago Process: 1170 ExecStart=/bin/bash -c export FLASK_APP=/opt/fzwk-access-source/app.py && flask run --host 0.0.0.0 (code=killed, signal=TERM) ... Mar 01 18:58:43 raspberrypi systemd[1]: fzwk-access.service: Start operation timed out. Terminating. Mar 01 18:58:43 raspberrypi systemd[1]: fzwk-access.service: Control process exited, code=killed, status=15/TERM Mar 01 18:58:43 raspberrypi systemd[1]: fzwk-access.service: Failed with result 'timeout'. Mar 01 18:58:43 raspberrypi systemd[1]: Failed to start fzwk-access. journalctl -xe delivers the following:
-- -- The process' exit code is 'killed' and its exit status is 15. Mar 01 18:58:43 raspberrypi systemd[1]: fzwk-access.service: Failed with result 'timeout'. -- Subject: Unit failed -- Defined-By: systemd -- Support: https://www.debian.org/support -- -- The unit fzwk-access.service has entered the 'failed' state with result 'timeout'. Mar 01 18:58:43 raspberrypi systemd[1]: Failed to start fzwk-access. -- Subject: A start job for unit fzwk-access.service has failed -- Defined-By: systemd -- Support: https://www.debian.org/support -- -- A start job for unit fzwk-access.service has finished with a failure. -- -- The job identifier is 513 and the job result is failed. Mar 01 18:58:43 raspberrypi sudo[1167]: pam_unix(sudo:session): session closed for user root Mar 01 18:59:03 raspberrypi systemd[1]: Configuration file /etc/systemd/system/fzwk-access.service is marked executable. Please remove executable permission bits. Proceeding anyway. 
chmod 644 fzwk-access.servicein the meantime, but that alone had not changed anything. I might have come to a solution, but will have to do some more digging/confirming. Once confirmed, I will put up an answer to help future me and hopefully others...