specify libvirt box override in provider block

Author: deargle

chef/dev/ub1404/Vagrantfile

@@ -1,23 +1,21 @@
 # This Vagrantfile can be used to quickly spin up a development instance of ub1404
 
 Vagrant.configure("2") do |config|
-  config.vm.define "dev" do |dev|
-    dev.vm.box = "bento/ubuntu-14.04"
-    dev.vm.box_version = "201808.24.0"
 
-    # alternatively, for libvirt, use the following box:
-    #config.vm.box = "peru/ubuntu-14.04-server-amd64"
-    #config.vm.box_version = "20190901.01"
-    dev.ssh.username = 'vagrant'
-    dev.ssh.password = 'vagrant'
-    dev.vm.network "forwarded_port", guest: 21, host:2121
+  config.vm.define "Metasploitable3-dev"
+  config.vm.box = "bento/ubuntu-14.04"
+  config.vm.box_version = "201808.24.0"
 
-    dev.vm.provider "virtualbox" do |v|
-      v.name = "Metasploitable3-ub1404-dev"
-      v.memory = 2048
-    end
+  config.vm.provider :libvirt do |libvirt, override|
+    override.vm.box = "peru/ubuntu-14.04-server-amd64"
+    override.vm.box_version = "20190901.01"
+    libvirt.memory = 2048
   end
 
+  config.ssh.username = 'vagrant'
+  config.ssh.password = 'vagrant'
+  config.vm.network "forwarded_port", guest: 21, host:2121
+
   # manually rsync recipe changes before re-provisioning. e.g.,
   # `vagrant rsync && vagrant provision`
   config.vm.provision "chef_solo" do |chef|