Login into an EC2 instance and verify whether ec2-user can run Docker commands without using sudo by executing following command:

[ec2-user@ip-54-196-74-162 ~]$ docker info

This will display system-wide information regarding the Docker installation, as shown in the following output:

 Containers: 1
 Running: 1
 Paused: 0
 Stopped: 0
 Images: 1
 ...
 Kernel Version: 4.9.62-21.56.amzn1.x86_64
 Operating System: Amazon Linux AMI 2017.09
 ...
 Live Restore Enabled: false