However, Dockerfiles are so popular because they run shell commands and permit 'socially' extending someone else shell commands; tacking commands onto the end of someone else's shell script is a natural process. /bin/sh is unreasonably effective at doing anything you need to a filesystem, and if the shell exposes a feature, it has probably been used in a Dockerfile somewhere.
Every other solution, especially declarative ones, tend to come up short when _layering_ images quickly and easily. However, I agree they're good if you control the entire declarative spec.
However, Dockerfiles are so popular because they run shell commands and permit 'socially' extending someone else shell commands; tacking commands onto the end of someone else's shell script is a natural process. /bin/sh is unreasonably effective at doing anything you need to a filesystem, and if the shell exposes a feature, it has probably been used in a Dockerfile somewhere.
Every other solution, especially declarative ones, tend to come up short when _layering_ images quickly and easily. However, I agree they're good if you control the entire declarative spec.