If you have an docker image local to your system, lets say version 1, and on the docker index there is a new version of that image (image 2), when you do a docker build, it will not check if there is a new version of image in the index before the build if it has one locally. This could cause some confusion, and could result in builds that aren't consistent across servers.

The way you need to handle this today, is to manually do the pull for your image before your build, and everything works fine, but it would be nice if we didn't need to do this.

Ideally docker build would always try to pull down the image from the index before the build to make sure the local one is up to date.

We could add a flag to the build to skip this step to preserve what we have now, but not sure if there is a valid use case were someone might need to do that.