System_Service
System Control service
Usage
Enabling a service or restarting a service can be done using systemctl command
sudo systemctl SERVICE_NAME start
sudo systemctl SERVICE_NAME stop
sudo systemctl SERVICE_NAME status
sudo systemctl SERVICE_NAME restart
Service on Boot
Enable auto run on system boot.
sudo systemctl enable SERVICE_NAME
List services startup
To check all the services which are being run on startup / boot of unix / linux OS.
sudo service --status-all
For simple startup service management on Raspberry Pi I recommend tool rcconf. It allows you to easily turn on/off services in /etc/init.d/. You can also see if they are enabled and will run at startup.
To install the tool
sudo apt-get install rcconf
sudo rcconf
And is very simple to use it with text UI
Super Use | How to tell which services run at startup
How to Use systemd to Launch Programs at Startup on Raspberry Pi
Delay
Just found my preferred solution for this and commenting in case it helps someone else. do the "sudo systemctl edit docker.service" as described by u/Parker_Hemphill, but instead of the straight delay I added a dependency on a USB mount-point. Like the below. This way the service don't even start until the various (space-separated) paths are available first.
[Unit]
#ExecStartPre=/bin/sleep 30
RequiresMountsFor=/media/localadmin/FILES /media/localadmin/PHOTOS
sleep 30 just left in there for my other's to see both options, but commented with the #
(Edit) changed service to unit