Start a service at boot time in systemd

I have placed a systemd service file in usr/lib/systemd/system/testfile.service. Here is the service file: [Unit] Description=Test service [Service] Type=notify ExecStart=/bin/dd.sh ExecReload=/bin/kill -HUP $MAINPID KillMode=process Restart=on-failure RestartSec=30s [Install] WantedBy=multi-user.target I tried to start the service at boot time these two ways: 1. Created a softlink for the file from /usr/lib/systemd/systemd to /etc/systemd/system/multi-user.target.wants (manually and by using systemctl enable command) and rebooted the system; testfile service started successfully at boot time. 2. Created a dependency in the existing running service file like After=testfile.service and Wants=testfile.service, then rebooted the system; testfile service started successfully. But when I place the file /usr/lib/systemd/system without using approaches 1 or 2 above, the service is not started. I feel that placing the service file in /usr/lib/systemd/system/ is enough for any service to start automatically, without creating the softlinks to wants directory or creating the dependency with the other services. Please let me know, how do I start a service at boot time which is present in the /usr/lib/systemd/system directory without using approaches 1 or 2 above? I have also created preset files in usr/lib/systemd/system-preset/ to disable and enable a few services, but it seems like those preset files were not executed: services which I have disabled in the preset file are still enabled after boot up. Please let me know how to debug this issue.