diff --git a/Vagrantfile b/Vagrantfile
index a014422b5e..9a6f897c0d 100644
--- a/Vagrantfile
+++ b/Vagrantfile
@@ -10,52 +10,53 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# Verify whether required plugins are installed.
+required_plugins = [ "vagrant-disksize" ]
+required_plugins.each do |plugin|
+  if not Vagrant.has_plugin?(plugin)
+    raise "The vagrant plugin #{plugin} is required. Please run `vagrant plugin install #{plugin}`"
+  end
+end
+
 Vagrant.configure(2) do |config|
 
+  # Configure all VM specs.
+  config.vm.provider "virtualbox" do |v|
+    v.memory = 8192
+    v.cpus = 4
+  end
+
+  # Configure the disk size.
+  disk_size = "60GB"
+
   config.vm.define "ubuntu1604" do |xenial|
     xenial.vm.box = "ubuntu/xenial64"
-    # Expand the disk to 60GB. You'll need
-    # the plugin disksize. Please run:
-    # vagrant plugin install vagrant-disksize
-    xenial.disksize.size = '60GB'
-    xenial.vm.provider "virtualbox" do |v|
-
-      v.memory = 8192
-      v.cpus = 4
-
-      # Now we can execute the build
-      config.vm.provision "shell", inline: <<-SHELL
-        sudo su -
-        cd /vagrant
-        ./scripts/gate-check-commit.sh
+    xenial.disksize.size = disk_size
+    config.vm.provision "shell",
+      privileged: true,
+      inline: <<-SHELL
+          cd /vagrant
+          ./scripts/gate-check-commit.sh
       SHELL
-
-    end
   end
 
   config.vm.define "centos7" do |centos7|
     centos7.vm.box = "centos/7"
-    centos7.disksize.size = '60GB'
-    centos7.vm.provider "virtualbox" do |v|
-
-      v.memory = 8192
-      v.cpus = 4
-
-      # Now we can execute the build
-      config.vm.provision "shell", inline: <<-SHELL
-        sudo su -
-        cd /vagrant
-        PART_START=$(parted /dev/sda --script unit MB print | awk '/^ 3 / {print $3}')
-        parted /dev/sda --script unit MB mkpart primary ${PART_START} 100%
-        parted /dev/sda --script set 4 lvm on
-        pvcreate /dev/sda4
-        vgextend VolGroup00 /dev/sda4
-        lvextend -l +100%FREE /dev/mapper/VolGroup00-LogVol00
-        xfs_growfs /dev/mapper/VolGroup00-LogVol00
-        ./scripts/gate-check-commit.sh
+    centos7.disksize.size = disk_size
+    # The CentOS build does not have growroot, so we
+    # have to do it ourselves.
+    config.vm.provision "shell",
+      privileged: true,
+      inline: <<-SHELL
+          cd /vagrant
+          PART_START=$(parted /dev/sda --script unit MB print | awk '/^ 3 / {print $3}')
+          parted /dev/sda --script unit MB mkpart primary ${PART_START} 100%
+          parted /dev/sda --script set 4 lvm on
+          pvcreate /dev/sda4
+          vgextend VolGroup00 /dev/sda4
+          lvextend -l +100%FREE /dev/mapper/VolGroup00-LogVol00
+          xfs_growfs /dev/mapper/VolGroup00-LogVol00
+          ./scripts/gate-check-commit.sh
       SHELL
-
-    end
   end
-
 end