Merge pull request #30553 from lewisdaly/21050-improve-user-namespace-docs

Updated dockerd docs with note about user namespaces
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Sebastiaan van Stijn 2017-02-03 19:48:06 -08:00 committed by GitHub
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@ -993,6 +993,19 @@ with user namespaces enabled or not. If the daemon is configured with user
namespaces, the Security Options entry in the response will list "userns" as
one of the enabled security features.
#### Behavior differences when user namespaces are enabled
When you start the Docker daemon with `--userns-remap`, Docker segregates the graph directory
where the images are stored by adding an extra directory with a name corresponding to the
remapped UID and GID. For example, if the remapped UID and GID begin with `165536`, all
images and containers running with that remap setting are located in `/var/lib/docker/165536.165536`
instead of `/var/lib/docker/`.
In addition, the files and directories within the new directory, which correspond to
images and container layers, are also owned by the new UID and GID. To set the ownership
correctly, you need to re-pull the images and restart the containers after starting the
daemon with `--userns-remap`.
### Detailed information on `subuid`/`subgid` ranges
Given potential advanced use of the subordinate ID ranges by power users, the