Ubuntu, CentOS command authority to solve the problem docker (sudo)

# Create docker group
weiyj ubuntu18 @: ~ $ docker the sudo the groupadd
the groupadd: Group 'docker' already EXISTS
# docker added to the current user group
weiyj ubuntu18 @: ~ $ $ -a the gpasswd the sudo the USER} {docker
Adding to Group User weiyj docker
# restart docker service
weiyj @ ubuntu18: ~ $ sudo service docker restart
# refresh docker group members
weiyj @ ubuntu18: ~ $ the newgrp - docker
# try again command _ ^ ^
weiyj @ ubuntu18: ~ $ docker ImagesRF Royalty Free
the REPOSITORY ID TAG the IMAGE CREATED SIZE
weiyj @ ubuntu18: ~ $