create: with LXC 2.1+ run lxc-update-config on new boxes

When running with LXC 2.1+, ensure that our boxes have up-to-date config
keys by running the `lxc-update-config` utility that ships with LXC
2.1+.

When the command doesn't exist (LXC <2.1), we do nothing.

ref #445

lib/vagrant-lxc/action/create.rb

@@ -19,14 +19,16 @@ def call(env)
               container_name = generate_container_name(env)
           end
 
-          env[:machine].provider.driver.create(
+          driver = env[:machine].provider.driver
+          driver.create(
             container_name,
             config.backingstore,
             config.backingstore_options,
             env[:lxc_template_src],
             env[:lxc_template_config],
             env[:lxc_template_opts]
           )
+          driver.update_config_keys
 
           env[:machine].id = container_name
 

lib/vagrant-lxc/driver.rb

@@ -45,6 +45,10 @@ def base_path
         Pathname.new("#{containers_path}/#{@container_name}")
       end
 
+      def config_path
+        base_path.join('config').to_s
+      end 
+
       def rootfs_path
         config_entry = config_string.match(/^lxc\.rootfs\s+=\s+(.+)$/)[1]
         case config_entry
@@ -72,7 +76,7 @@ def mac_address
       end
 
       def config_string
-        @sudo_wrapper.run('cat', base_path.join('config').to_s)
+        @sudo_wrapper.run('cat', config_path)
       end
 
       def create(name, backingstore, backingstore_options, template_path, config_file, template_options = {})
@@ -240,6 +244,12 @@ def prune_customizations
         write_config(contents)
       end
 
+      def update_config_keys
+        @cli.update_config(config_path)
+      rescue Errors::ExecuteError
+        # not on LXC 2.1+. Doesn't matter, ignore.
+      end
+
       protected
 
       def write_customizations(customizations)
@@ -260,8 +270,8 @@ def write_config(contents)
           file.chmod 0644
           file.write contents
           file.close
-          @sudo_wrapper.run 'cp', '-f', file.path, base_path.join('config').to_s
-          @sudo_wrapper.run 'chown', 'root:root', base_path.join('config').to_s
+          @sudo_wrapper.run 'cp', '-f', file.path, config_path
+          @sudo_wrapper.run 'chown', 'root:root', config_path
         end
       end
     end

lib/vagrant-lxc/driver/cli.rb

@@ -42,6 +42,10 @@ def config(param)
           run(:config, param).gsub("\n", '')
         end
 
+        def update_config(path)
+          run('update-config', '-c', path)
+        end
+
         def state
           if @name && run(:info, '--name', @name, retryable: true) =~ /^state:[^A-Z]+([A-Z]+)$/i
             $1.downcase.to_sym

templates/sudoers.rb.erb

@@ -119,6 +119,7 @@ Whitelist.add '<%= cmd_paths['lxc_bin'] %>/lxc-shutdown', '--name', /.*/
 Whitelist.add '<%= cmd_paths['lxc_bin'] %>/lxc-attach', '--name', /.*/, '**'
 Whitelist.add '<%= cmd_paths['lxc_bin'] %>/lxc-attach', '-h'
 Whitelist.add '<%= cmd_paths['lxc_bin'] %>/lxc-config', 'lxc.lxcpath'
+Whitelist.add '<%= cmd_paths['lxc_bin'] %>/lxc-update-config', '-c', /.*/
 
 ##
 # Commands from driver/action/remove_temporary_files.rb