Since Docker 20.10, it supports running the daemon in rootless mode.
It's possible to know if the docker daemon is running in rootless mode through docker info:
$ docker info
[...]
Server:
[...]
Security Options:
rootless
[...]
My question is: from within a container (i.e. in the entrypoint), how can I check if it is running in rootless mode?
PS: without relying on the user namespace detection, as not all the userns scenarios are tied to docker daemon's rootless mode.