Windows
ArcGIS License Manager starts automatically after a computer reboot or after the installation is complete.
Also refer to Starting and stopping the License Manager.
Linux
Once you have installed and started ArcGIS License Manager on your network, configure the license server to start automatically when the system boots, even though it is not required.
Platform-specific instructions for this operation on Linux are found in the license.boot or arclicense.service file located in your ArcGIS License Manager installation location.
To start ArcGIS License Manager automatically at boot time, you must use the license.boot or arclicense.service file, and you will need to modify this file to reflect your system information.
Also refer to Starting and stopping the License Manager.