如何删除Docker的图像?

I've the following images:

我下面的图片:

alex@alexvps:~$ sudo docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
<none>              <none>              70c0e19168cf        5 days ago          1.069 GB
<none>              <none>              c2ce80b62174        8 days ago          399.2 MB
<none>              <none>              60afe4036d97        8 days ago          325.1 MB
alex@ale