Here is a blog that talks about some of its features.
Our main goal was to make this simple. I was asked by a fellow engineer about a feature that docker has for copying a file out of a container onto the host. "docker cp". In docker this ends up being a client server operation, and required someone to code it up. We don't have this feature in buildah. :^(
BUT, buildah gives you the primitives you need to do simpler functionality and allows you to use the full power of bash. If I want to copy a file out of a container, I can simply mount the container and copy it out.
# mnt=$(buildah mount CONTAINER_ID)
# cp $mnt/PATHTOSRC /PATHTODEST
# buildah umount CONTAINER_ID
The beauty of this is we could use lots of tools, I could scp if I wanted to copy to another machine, or rsync, or ftp...
Once your have the container mounted up, you can use any bash command on it, to move files in or out.
buildah == simplicity