Fixes #9763, #10300: Split out how hostname is set with Debian hosts

Prior to this commit, the hostname was set with one big bash script and
attempted to determine what tools are available. This commit changes
that by splitting out that tool check on the Vagrant side of things with
the GuestInspection class, and adds back restarting networking to get a
DHCP lease with the change rather than using `dhclient`. This pattern
matches how hostnames are set in the redhat capability.

plugins/guests/debian/cap/change_host_name.rb

@@ -2,6 +2,9 @@ module VagrantPlugins
   module GuestDebian
     module Cap
       class ChangeHostName
+
+        extend Vagrant::Util::GuestInspection::Linux
+
         def self.change_host_name(machine, name)
           comm = machine.communicate
 
@@ -10,11 +13,6 @@ module VagrantPlugins
             comm.sudo <<-EOH.gsub(/^ {14}/, '')
               # Set the hostname
               echo '#{basename}' > /etc/hostname
-              hostname -F /etc/hostname
-
-              if command -v hostnamectl; then
-                hostnamectl set-hostname '#{basename}'
-              fi
 
               # Prepend ourselves to /etc/hosts
               grep -w '#{name}' /etc/hosts || {
@@ -28,6 +26,13 @@ module VagrantPlugins
               # Update mailname
               echo '#{name}' > /etc/mailname
 
+            EOH
+
+            if hostnamectl?(comm)
+              comm.sudo("hostnamectl set-hostname '#{basename}'")
+            else
+              comm.sudo <<-EOH.gsub(/^ {14}/, '')
+              hostname -F /etc/hostname
               # Restart hostname services
               if test -f /etc/init.d/hostname; then
                 /etc/init.d/hostname start || true
@@ -36,11 +41,19 @@ module VagrantPlugins
               if test -f /etc/init.d/hostname.sh; then
                 /etc/init.d/hostname.sh start || true
               fi
-              if test -x /sbin/dhclient ; then
-                /sbin/dhclient -r
-                /sbin/dhclient -nw
-              fi
-            EOH
+              EOH
+            end
+
+            restart_command = "/etc/init.d/networking restart"
+
+            if systemd?(comm)
+              if systemd_networkd?(comm)
+                restart_command = "systemctl restart systemd-networkd.service"
+              elsif systemd_controlled?(comm, "NetworkManager.service")
+                restart_command = "systemctl restart NetworkManager.service"
+              end
+            end
+            comm.sudo(restart_command)
           end
         end
       end

test/unit/plugins/guests/debian/cap/change_host_name_test.rb

@@ -20,14 +20,81 @@ describe "VagrantPlugins::GuestDebian::Cap::ChangeHostName" do
 
   describe ".change_host_name" do
     let(:cap) { caps.get(:change_host_name) }
-
     let(:name) { 'banana-rama.example.com' }
+    let(:systemd) { true }
+    let(:hostnamectl) { true }
+    let(:networkd) { true }
+    let(:network_manager) { false }
+
+    before do
+      allow(cap).to receive(:systemd?).and_return(systemd)
+      allow(cap).to receive(:hostnamectl?).and_return(hostnamectl)
+      allow(cap).to receive(:systemd_networkd?).and_return(networkd)
+      allow(cap).to receive(:systemd_controlled?).with(anything, /NetworkManager/).and_return(network_manager)
+    end
 
     it "sets the hostname if not set" do
       comm.stub_command("hostname -f | grep '^#{name}$'", exit_code: 1)
       cap.change_host_name(machine, name)
-      expect(comm.received_commands[1]).to match(/hostname -F \/etc\/hostname/)
-      expect(comm.received_commands[1]).to match(/hostname.sh start/)
+      expect(comm.received_commands[1]).to match(/echo 'banana-rama' > \/etc\/hostname/)
+    end
+
+    context "when hostnamectl is in use" do
+      let(:hostnamectl) { true }
+
+      it "sets hostname with hostnamectl" do
+        cap.change_host_name(machine, name)
+        expect(comm.received_commands[2]).to match(/hostnamectl/)
+      end
+    end
+
+    context "when hostnamectl is not in use" do
+      let(:hostnamectl) { false }
+
+      it "sets hostname with hostname command" do
+        cap.change_host_name(machine, name)
+        expect(comm.received_commands[2]).to match(/hostname -F/)
+      end
+    end
+
+    context "restarts the network" do
+      context "when networkd is in use" do
+        let(:networkd) { true }
+
+        it "restarts networkd with systemctl" do
+          cap.change_host_name(machine, name)
+          expect(comm.received_commands[3]).to match(/systemctl restart systemd-networkd/)
+        end
+      end
+
+      context "when NetworkManager is in use" do
+        let(:networkd) { false }
+        let(:network_manager) { true }
+
+        it "restarts NetworkManager with systemctl" do
+          cap.change_host_name(machine, name)
+          expect(comm.received_commands[3]).to match(/systemctl restart NetworkManager/)
+        end
+      end
+
+      context "when networkd and NetworkManager are not in use" do
+        let(:networkd) { false }
+        let(:network_manager) { false }
+
+        it "restarts the network using service" do
+          cap.change_host_name(machine, name)
+          expect(comm.received_commands[3]).to match(/networking restart/)
+        end
+      end
+
+      context "when systemd is not in use" do
+        let(:systemd) { false }
+
+        it "restarts the network using service" do
+          cap.change_host_name(machine, name)
+          expect(comm.received_commands[3]).to match(/networking restart/)
+        end
+      end
     end
 
     it "does not set the hostname if unset" do