I almost exclusively run FEniCS using Docker and have recently noticed that building images from Dockerfiles often results in a lot of
<none>:<none> images showing up when I run
docker images. This is different from images labelled the same showing up when running
docker images -a (in that case they are “intermediate” images since Docker images are composed of layers).
<none>:<none> images that show up when running
docker images are references to old images after for example updating an image since updating an image does not actually update it, but creates a new image for the new version and leaves the old one dangling as a
<none>:<none>. Docker does not have its own garbage collection, so this has to be done manually using the following terminal command.