Create a -G option that specifies the group which unix sockets belong to.

Docker-DCO-1.1-Signed-off-by: Evan Krall <krall@yelp.com> (github: EvanKrall)

docs/sources/installation/ubuntulinux.rst

@@ -182,9 +182,12 @@ daemon will make the ownership of the Unix socket read/writable by the
 *docker* group when the daemon starts. The ``docker`` daemon must
 always run as the root user, but if you run the ``docker`` client as a user in
 the *docker* group then you don't need to add ``sudo`` to all the
-client commands.  
+client commands. As of 0.9.0, you can specify that a group other than ``docker``
+should own the Unix socket with the ``-G`` option.
+
+.. warning:: The *docker* group (or the group specified with ``-G``) is
+   root-equivalent.
 
-.. warning:: The *docker* group is root-equivalent.
 
 **Example:**
 

docs/sources/reference/commandline/cli.rst

@@ -71,6 +71,7 @@ Commands
     Usage of docker:
       -D, --debug=false: Enable debug mode
       -H, --host=[]: Multiple tcp://host:port or unix://path/to/socket to bind in daemon mode, single connection otherwise. systemd socket activation can be used with fd://[socketfd].
+      -G, --group="docker": Group to assign the unix socket specified by -H when running in daemon mode; use '' (the empty string) to disable setting of a group
       --api-enable-cors=false: Enable CORS headers in the remote API
       -b, --bridge="": Attach containers to a pre-existing network bridge; use 'none' to disable container networking
       --bip="": Use this CIDR notation address for the network bridge's IP, not compatible with -b