Recently trying out docker and was playing with Dockerfile. I ran my Dockerfile a few times and it made a few containers for the different build tries.
sudo docker build -t rockerboo/web .
docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
rockerboo/web latest 57575666258f 2 minutes ago 542.7 MB
<none> <none> e157a88c6e6b 2 minutes ago 542.7 MB
<none> <none> 2b823e316c3b 10 minutes ago 542.7 MB
<none> <none> 97205609a8e8 32 minutes ago 542.6 MB
<none> <none> 1ff57f10b000 33 minutes ago 541.8 MB
<none> <none> 759adaaf687e 41 minutes ago 541.8 MB
Trying to remove an image docker rmi 57575666258f it would say Error: Conflict, 57575666258f wasn't deleted. This error is trying to tell you that it can't remove the image because its being used by a container.
To get a list of all the containers docker ps -a and then you can see the containers that are using the image.
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
0d4c1e223500 57575666258f /bin/sh -c service p 27 minutes ago Exit 0 sick_newton
f0923d332692 57575666258f /bin/sh -c service p 27 minutes ago Exit 0 hungry_tesla
Remove the containers.
docker rm 0d4c1e223500; docker rm f0923d332692
Now you can properly remove the images.
docker rmi 57575666258f