My nodes Digital Ocean are UNREACHABLE from docker cloud

I have worked with docker cloud for a month. My nodes are created as described at for a Digital Ocean account. But I’ve decided to update the operating system of the node (I access through ssh):

$ sudo apt update && sudo apt upgrade 

Then increase the swap memory as described here:

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  • I finally reboot the system:

    $ Sudo reboot 

    But after this my system is already inaccessible from Docker cloud, status nodes is UNREACHABLE

    When running

    $ docker version 

    I get:

        Docker version 
         Version: 1.11.2-cs5 
         API version: 1.23 
         Go version: go1.5.4 
         Git commit: d364ea1 
         Built: Tue Sep 13 15:26:43 2016 
         OS / Arch: linux / amd64 
    Can not connect to the Docker daemon. Is the docker daemon running on this host?

    How can I recover these nodes? I appreciate your help.

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