According to Government Gazette 2661/18.06.2021 (Article four) the following applies for the entry of truck drivers into Greece from Saturday, 19th of June 2021 at 06:00 until Saturday, 26th of June 2021 at 06:00:
Trucks drivers, regardless of nationality, performing freight transportation on the Italy-Greece routes (to the ports of Patras, Igoumenitsa and Corfu) must submit at departure port a COVID-19 self-test declaration of negative result before boarding the ship. Upon arrival at the Greek port of destination, drivers are required to present to the competent Greek authorities the above self-test declaration and are subject to mandatory examination for rapid detection of coronavirus COVID-19 antigen (rapid test).
You will find attached the self-test result declaration form.
Truck drivers are advised to arrive at the port of departure on time in order to facilitate the pre-boarding inspection process.