If you use the command wrong eg.
$ sudo docker tag 37bcb6bfd184 wyaeld/postgresql:9.3
$ sudo docker images
REPOSITORY TAG ID CREATED SIZE
wyaeld/postgresql:9.3 latest 37bcb6bfd184 About a minute ago 12.29 kB (virtual 701 MB)
rather than
sudo docker tag 37bcb6bfd184 wyaeld/postgresql 9.3
The problem is after you have done so, you can't get rid of it with rmi.
sudo docker rmi wyaeld/postgresql
Error: No such image: wyaeld/postgresql
sudo docker rmi wyaeld/postgresql:9.3
Error: No such image: wyaeld/postgresql:9.3
If you use the command wrong eg.
rather than
The problem is after you have done so, you can't get rid of it with rmi.