Support include_offline boxes.

If include_offline is enabled, we loop over all available boxes picking
those with the correct provider.

If a box has no private ip set or is offline, it is skipped (a warning is shown).
The lambda that gets the ip will return nil for the boxes.

lib/vagrant-hostmanager/hosts_file.rb

@@ -17,7 +17,7 @@ module VagrantPlugins
               next if ip
             end
           end
-          ip || machine.ssh_info[:host]
+          ip || (machine.ssh_info ? machine.ssh_info[:host] : nil)
         end
 
         # create the temporary hosts file
@@ -29,17 +29,22 @@ module VagrantPlugins
               machines << machine = env.machine(name, provider)
               host = machine.config.vm.hostname || name
               ip = get_ip_address.call(machine)
-              host_aliases = machine.config.hostmanager.aliases.join("\s").chomp
-              machine.env.ui.info I18n.t('vagrant_hostmanager.action.add_host', {
-                :ip       => ip,
-                :host     => host,
-                :aliases  => host_aliases,
-              })
-              file << "#{ip}\t#{host}\s#{host_aliases}\n"
+              if ip
+                host_aliases = machine.config.hostmanager.aliases.join("\s").chomp
+                machine.env.ui.info I18n.t('vagrant_hostmanager.action.add_host', {
+                  :ip       => ip,
+                  :host     => host,
+                  :aliases  => host_aliases,
+                })
+                file << "#{ip}\t#{host}\s#{host_aliases}\n"
+              else
+                machine.env.ui.warn I18n.t('vagrant_hostmanager.action.host_no_ip', {
+                  :name => name,
+                })
+              end
             end
           end
         end
-
         machines
       end
 
@@ -57,10 +62,26 @@ module VagrantPlugins
       end
 
       private
+      # Either use the active machines, or loop over all available machines and
+      # get those with the same provider (aka, ignore boxes that throw MachineNotFound errors).
+      #
       # Returns an array with the same structure as env.active_machines:
       # [ [:machine, :virtualbox], [:foo, :virtualbox] ]
       def get_machines(env, provider)
-        env.active_machines
+        if env.config_global.hostmanager.include_offline?
+          machines = []
+          env.machine_names.each do |name|
+            begin
+              m = env.machine(name, provider)
+              machines << [name, provider]
+            rescue Vagrant::Errors::MachineNotFound => ex
+              # ignore this box.
+            end
+          end
+          machines
+        else
+          env.active_machines
+        end
       end
 
     end

locales/en.yml

@@ -2,6 +2,7 @@ en:
   vagrant_hostmanager:
     action:
       add_host: "Adding /etc/hosts entry: %{ip} %{host} %{aliases}"
+      host_no_ip: "Could not determine ip for machine '%{name}': no private ip configured or machine not up."
       update: "[%{name}] Updating /etc/hosts file"
     config:
       not_a_bool: "A value for %{config_key} can only be true or false, not type '%{value}'"