Add option to allow/disable fstab modification

Defaults to allow modification of fstab

plugins/guests/linux/cap/persist_mount_shared_folder.rb

@@ -8,6 +8,13 @@ module VagrantPlugins
       class PersistMountSharedFolder
         extend SyncedFolder::UnixMountHelpers
 
+        # Inserts fstab entry for a set of synced folders. Will fully replace
+        # the currently managed group of Vagrant managed entries. Note, passing
+        # empty list of folders will just remove entries      
+        # 
+        # @param [Machine] machine The machine to run the action on
+        # @param [Map<String, Map>] A map of folders to add to fstab
+        # @param [String] mount type, ex. vboxfs, cifs, etc
         def self.persist_mount_shared_folder(machine, fstab_folders, mount_type)
           if fstab_folders.empty?
             self.remove_vagrant_managed_fstab(machine)

plugins/kernel_v2/config/vm.rb

@@ -22,6 +22,7 @@ module VagrantPlugins
       DEFAULT_VM_NAME = :default
 
       attr_accessor :allowed_synced_folder_types
+      attr_accessor :allow_fstab_modification
       attr_accessor :base_mac
       attr_accessor :base_address
       attr_accessor :boot_timeout
@@ -56,6 +57,7 @@ module VagrantPlugins
         @logger = Log4r::Logger.new("vagrant::config::vm")
 
         @allowed_synced_folder_types   = UNSET_VALUE
+        @allow_fstab_modification      = UNSET_VALUE
         @base_mac                      = UNSET_VALUE
         @base_address                  = UNSET_VALUE
         @boot_timeout                  = UNSET_VALUE
@@ -452,6 +454,7 @@ module VagrantPlugins
 
       def finalize!
         # Defaults
+        @allow_fstab_modification = true if @allow_fstab_modification == UNSET_VALUE
         @allowed_synced_folder_types = nil if @allowed_synced_folder_types == UNSET_VALUE
         @base_mac = nil if @base_mac == UNSET_VALUE
         @base_address = nil if @base_address == UNSET_VALUE
@@ -928,6 +931,12 @@ module VagrantPlugins
           end
         end
 
+        if ![TrueClass, FalseClass].include?(@allow_fstab_modification.class)
+          errors["vm"] << I18n.t("vagrant.config.vm.config_type",
+            option: "allow_fstab_modification", given: @allow_fstab_modification.class, required: "Boolean"
+          )
+        end
+
         errors
       end
 

plugins/providers/virtualbox/synced_folder.rb

@@ -61,6 +61,10 @@ module VagrantPlugins
           end
         end
         if machine.guest.capability?(:persist_mount_shared_folder)
+          # If Vagrant has been configured to not allow fstab modification, then
+          # execute the guest capability with an empty list in order to ensure
+          # there is no Vagrant managed fstab entries.
+          fstab_folders = [] if !machine.config.vm.allow_fstab_modification
           machine.guest.capability(:persist_mount_shared_folder, fstab_folders, "vboxsf")
         end
       end

templates/locales/en.yml

@@ -1947,6 +1947,7 @@ en:
         box_download_options_not_converted: |-
           Something went wrong converting VM config `box_download_options`. Value for provided key '%{missing_key}' is invalid type. Should be String or Bool
         clone_and_box: "Only one of clone or box can be specified."
+        config_type: "Found '%{option}' specified as type '%{given}', should be '%{required}'"
         hostname_invalid_characters: |-
           The hostname set for the VM '%{name}' should only contain letters, numbers,
           hyphens or dots. It cannot start with a hyphen or dot.

test/unit/plugins/providers/virtualbox/synced_folder_test.rb

@@ -6,10 +6,24 @@ require Vagrant.source_root.join("plugins/providers/virtualbox/synced_folder")
 
 describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
   include_context "unit"
+
+  let(:vm_config) do
+    double("vm_config").tap do |vm_config|
+      allow(vm_config).to receive(:allow_fstab_modification).and_return(true)
+    end
+  end
+
+  let(:machine_config) do
+    double("machine_config").tap do |top_config|
+      allow(top_config).to receive(:vm).and_return(vm_config)
+    end
+  end
+
   let(:machine) do
     double("machine").tap do |m|
       allow(m).to receive(:provider_config).and_return(VagrantPlugins::ProviderVirtualBox::Config.new)
       allow(m).to receive(:provider_name).and_return(:virtualbox)
+      allow(m).to receive(:config).and_return(machine_config)
     end
   end
 
@@ -73,6 +87,21 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
       test_folders = folders.merge(no_guestpath_folder)
       subject.enable(machine, test_folders, nil)
     end
+
+    context "fstab modification disabled" do
+      before do
+       allow(vm_config).to receive(:allow_fstab_modification).and_return(false)
+      end
+
+      it "should not persist folders" do
+        expect(guest).to receive(:capability).with(:mount_virtualbox_shared_folder, "folder", any_args)
+        expect(guest).not_to receive(:capability).with(:mount_virtualbox_shared_folder, "no_guestpath_folder", any_args)
+        expect(guest).to receive(:capability?).with(:persist_mount_shared_folder).and_return(true)
+        expect(guest).to receive(:capability).with(:persist_mount_shared_folder, [], "vboxsf")
+        test_folders = folders.merge(no_guestpath_folder)
+        subject.enable(machine, test_folders, nil)
+      end
+    end
   end
 
   describe "#prepare" do

website/pages/docs/vagrantfile/machine_settings.mdx

@@ -16,6 +16,11 @@ machine that Vagrant manages.
 
 ## Available Settings
 
+- `config.vm.allow_fstab_modification` (boolean) - If true, will add fstab
+  entries for synced folders. If false, no modifications to fstab will be made 
+  by Vagrant. Note, this may mean that folders will not be automatically mounted
+  on machine reboot. Defaults to true.
+
 - `config.vm.base_mac` (string) - The MAC address to be assigned to the default
   NAT interface on the guest. _Support for this option is provider dependent._