guests/redhat: install Docker on EL7 properly [GH-4402]

CHANGELOG.md

@@ -69,6 +69,7 @@ BUG FIXES:
   - guests/linux: Show more verbose error when shared folder mount fails.
       [GH-4403]
   - guests/redhat: NFS setup should use systemd for RH7+ [GH-4228]
+  - guests/redhat: Detect RHEL 7 (and CentOS) and install Docker properly. [GH-4402]
   - guests/smartos: Use `pfexec` for rsync. [GH-4274]
   - guests/windows: Reboot after hostname change. [GH-3987]
   - hosts/arch: NFS works with latest versions. [GH-4224]

plugins/guests/redhat/cap/flavor.rb

@@ -0,0 +1,23 @@
+module VagrantPlugins
+  module GuestRedHat
+    module Cap
+      class Flavor
+        def self.flavor(machine)
+          # Read the version file
+          output = ""
+          machine.communicate.sudo("cat /etc/redhat-release") do |type, data|
+            output += data if type == :stdout
+          end
+          output.chomp!
+
+          # Detect various flavors we care about
+          if output =~ /(CentOS|Red Hat Enterprise) Linux release 7/i
+            return :rhel_7
+          else
+            return :rhel
+          end
+        end
+      end
+    end
+  end
+end

plugins/guests/redhat/plugin.rb

@@ -21,6 +21,11 @@ module VagrantPlugins
         Cap::ConfigureNetworks
       end
 
+      guest_capability("redhat", "flavor") do
+        require_relative "cap/flavor"
+        Cap::Flavor
+      end
+
       guest_capability("redhat", "network_scripts_dir") do
         require_relative "cap/network_scripts_dir"
         Cap::NetworkScriptsDir

plugins/provisioners/docker/cap/redhat/docker_install.rb

@@ -8,6 +8,23 @@ module VagrantPlugins
               machine.ui.warn(I18n.t("vagrant.docker_install_with_version_not_supported"))
             end
 
+            case machine.guest.capability("flavor")
+            when :rhel_7
+              docker_install_rhel7(machine)
+            else
+              docker_install_default(machine)
+            end
+          end
+
+          def docker_install_rhel7(machine)
+            machine.communicate.tap do |comm|
+              comm.sudo("yum -y install docker")
+              comm.sudo("systemctl start docker.service")
+              comm.sudo("systemctl enable docker.service")
+            end
+          end
+
+          def docker_install_default(machine)
             machine.communicate.tap do |comm|
               if ! comm.test("rpm -qa | grep epel-release")
                 comm.sudo("rpm -ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm")