Add --uts=host to allow sharing the UTS namespace

Signed-off-by: Darren Shepherd <darren@rancher.com>

docs/sources/reference/commandline/cli.md

@@ -991,6 +991,8 @@ Creates a new container.
       --oom-kill-disable=false   Whether to disable OOM Killer for the container or not
       -P, --publish-all=false    Publish all exposed ports to random ports
       -p, --publish=[]           Publish a container's port(s) to the host
+      --pid=""                   PID namespace to use
+      --uts=""                   UTS namespace to use
       --privileged=false         Give extended privileges to this container
       --read-only=false          Mount the container's root filesystem as read only
       --restart="no"             Restart policy (no, on-failure[:max-retry], always)
@@ -1958,6 +1960,7 @@ To remove an image using its digest:
       -P, --publish-all=false    Publish all exposed ports to random ports
       -p, --publish=[]           Publish a container's port(s) to the host
       --pid=""                   PID namespace to use
+      --uts=""                   UTS namespace to use
       --privileged=false         Give extended privileges to this container
       --read-only=false          Mount the container's root filesystem as read only
       --restart="no"             Restart policy (no, on-failure[:max-retry], always)

docs/sources/reference/run.md

@@ -157,6 +157,7 @@ called a digest. As long as the input used to generate the image is unchanged,
 the digest value is predictable and referenceable.
 
 ## PID settings (--pid)
+
     --pid=""  : Set the PID (Process) Namespace mode for the container,
            'host': use the host's PID namespace inside the container
 
@@ -177,6 +178,23 @@ within the container.
 This command would allow you to use `strace` inside the container on pid 1234 on
 the host.
 
+## UTS settings (--uts)
+
+    --uts=""  : Set the UTS namespace mode for the container,
+           'host': use the host's UTS namespace inside the container
+
+The UTS namespace is for setting the hostname and the domain that is visible
+to running processes in that namespace.  By default, all containers, including
+those with `--net=host`, have their own UTS namespace.  The `host` setting will
+result in the container using the same UTS namespace as the host.
+
+You may wish to share the UTS namespace with the host if you would like the
+hostname of the container to change as the hostname of the host changes.  A
+more advanced use case would be changing the host's hostname from a container.
+
+> **Note**: `--uts="host"` gives the container full access to change the
+> hostname of the host and is therefore considered insecure.
+
 ## IPC settings (--ipc)
 
     --ipc=""  : Set the IPC mode for the container,