[request] It fails to start service
Since the knot dns resolver of Service files of Unit column Wants and Before, After has not been set, it will fail to start the service when you start your computer.
Breaking ordering cycle by deleting job kresd.service/start
[ 8.493987] systemd[1]: sockets.target: Found ordering cycle on sockets.target/start
[ 8.494007] systemd[1]: sockets.target: Found dependency on kresd.service/start
[ 8.494015] systemd[1]: sockets.target: Found dependency on basic.target/start
[ 8.494023] systemd[1]: sockets.target: Found dependency on sockets.target/start
[ 8.494030] systemd[1]: sockets.target: Breaking ordering cycle by deleting job kresd.service/start
[ 8.494039] systemd[1]: kresd.service: Job kresd.service/start deleted to break ordering cycle starting with sockets.target/start
So, by adding to the Service file as shown below, I think it is better you to start waiting for the network service.
Wants=network.target nss-lookup.target
Before=nss-lookup.target
After=network-online.target
env
$ hostnamectl
Static hostname: dns02
Icon name: computer
Machine ID: 24b8da0506634e5f8905b90ef91caf6b
Boot ID: 5d8e534f2e134e31bc6ca5f8783ebb24
Operating System: Ubuntu 16.04.1 LTS
Kernel: Linux 3.14.79-odroidc2
Architecture: arm64