I am trying to understand this flag DOCKER_CONTENT_TRUST=1 but not able to figure it out. How does it effect pushing images and pulling images, let's say from docker hub?
DOCKER_CONTENT_TRUST=1 this is env variable to enable Docker content trust by default it is in disable mode.
read more about DCT in official docs DCT docs
For specific build/push/pull you can use as docker command line flag as well
--disable-content-trust=false or --disable-content-trust=true