Update:
Issue “netdata fails to start after reboot” is solved.
The root cause was an entry in /etc/fstab:
After deleting this line
tmpfs /var/tmp tmpfs size=25M,noatime,lazytime,nodev,nosuid,mode=1777
netdata is starting after reboot.
However I still cannot disable DietPi service control of netdata.
With this status before reboot
[code]root@eddie:~# dietpi-services systemd_controlled netdata
DietPi-Services
─────────────────────────────────────────────────────
Mode: systemd_controlled netdata
[ OK ] DietPi-Services | systemd_controlled : netdata
the service is started after reboot automatically.
root@eddie:~# dietpi-services status netdata
DietPi-Services
─────────────────────────────────────────────────────
Mode: status netdata
[ OK ] DietPi-Services | netdata active (running) since Fri 2022-03-11 16:45:39 CET; 3min 36s ago
This means I have no control of netdata.service at all.