Systemd run script after mount

mount_x.service

# original: https://askubuntu.com/questions/25071/how-to-run-a-script-when-a-specific-flash-drive-is-mounted
# you can find your device unit with: sudo systemctl list-units -t mount
# put this into /etc/systemd/system/your.service

[Unit]
Description=SharedMountTrigger
Requires=mnt-shared.mount
After=mnt-shared.mount

[Service]
ExecStart=/usr/local/bin/x-start-docker

[Install]
WantedBy=mnt-shared.mount

# Then you have to start/enable the service:
# sudo systemctl start your.service
# sudo systemctl enable your.service