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The container root certainly has UID 0, but it has reduced system capabilities. The irony of user namespaces is that they provide additional capabilities, but g
by ewindisch 12y ago
The container root certainly has UID 0, but it has reduced system capabilities. The irony of user namespaces is that they provide additional capabilities, but give you a fake UID-0 while "actually" running as a higher UID.
This distinction is important because it's why, in practice, Docker's current approach has proven to be more secure than user namespaces. User namespaces allow various operations that would be outright denied under a Docker container's very-real-but-very-limited root user.
However, yes, user namespaces are coming to Docker. It's a highly desired feature and eventually userns will mature.
- lclarkmichalek 12y agoI'd be interested to see how the current approach has been proven to be more secure than userns, though I can well beleive it. I do agree that dropping capabilities is good, however, even with the reduced capabilities provided, the kernel is still a very large target, and so I would sleep a lot easier with userns active (in addition to capability (and mb even seccomp ;)) filtering) on all my containers. It just seems like such a free win (and I appreciate how that must sound to the people who are implementing it).