Is this a Linux kernel namespace that is disabled by default and must be enabled at Docker engine runtime to be used? Solution: user

The `user` namespace, which maps container UIDs/GIDs to different UIDs/GIDs on the host, is disabled by default in Docker due to its advanced security implications and potential complexities. It must be explicitly configured, for instance via the `userns-remap` daemon option, to be utilized for rootless container execution.

The `user` namespace is specifically designed for enhanced security through user ID remapping and is an opt-in feature, not enabled by default in Docker.