But docker runs still with root privileges (or your user must be in the docker group, which is equivalent to root - so is also in the official documentation explained)
I'm a big fan of people supplying pre-built docker images because it lets me try out their software in what I assume to be a sandbox. I'm a little less wary when it comes to docker -- almost to the point of being nonchalant, running random images willy-nilly without digging into the source code even a tiny bit. Granted, that behavior is probably gonna bite me in the ass one day. But it's definitely better than the `curl http://example.com | bash -` and `sudo make install` patterns.
Whenever I see someone's instructions telling me to use `docker --network=host` or `docker --privileged`, I can't help but panic a little... "Am I going to regret running this developer's code as root on my machine?" A little justification from the OP eases my mind, that's all. Which he did :)
I wouldn't agree that it's trivially possible to breakout of a default configured Docker container, not every attacker is packing a Linux Privesc 0-day and the knowledge to use it.
Containers are broken by default because they share a kernel. If you want to use a container to have a replicable build environment fine - but for operational use in the context of "being secure" - no no no no.
Probably aind doesn't work with rootless Docker currently mostly because of squashfs stuff, but I believe we can workaround that relatively easily.
That's why --privileged is generally a bad idea, unless you really need it, as it removes the isolation that Docker adds.