Fixes #10170: Check for modinfo in /sbin (#11178)

Check for modinfo in /sbin if it doesn't appear on the PATH.

If it's not found on the PATH or in /sbin, the command will default back to modinfo so the user sees the error message about adding it to their PATH.

plugins/hosts/linux/cap/nfs.rb

@@ -93,7 +93,7 @@ module VagrantPlugins
               "systemctl --no-pager --no-legend --plain list-unit-files --all --type=service " \
                 "| grep #{nfs_service_name_systemd}").exit_code == 0
           else
-            Vagrant::Util::Subprocess.execute("modinfo", "nfsd").exit_code == 0 ||
+            Vagrant::Util::Subprocess.execute(modinfo_path, "nfsd").exit_code == 0 ||
               Vagrant::Util::Subprocess.execute("grep", "nfsd", "/proc/filesystems").exit_code == 0
           end
         end
@@ -261,6 +261,24 @@ module VagrantPlugins
           Vagrant::Util::Subprocess.execute(*Shellwords.split(check_command)).exit_code == 0
         end
 
+        def self.modinfo_path
+          if !defined?(@_modinfo_path)
+            @_modinfo_path = Vagrant::Util::Which.which("modinfo")
+
+            if @_modinfo_path.to_s.empty?
+              path = "/sbin/modinfo"
+              if File.file?(path)
+                @_modinfo_path = path
+              end
+            end
+
+            if @_modinfo_path.to_s.empty?
+              @_modinfo_path = "modinfo"
+            end
+          end
+          @_modinfo_path
+        end
+
         # @private
         # Reset the cached values for capability. This is not considered a public
         # API and should only be used for testing.

test/unit/plugins/hosts/linux/cap/nfs_test.rb

@@ -337,4 +337,50 @@ EOH
       end
     end
   end
+
+  describe ".modinfo_path" do
+    let(:cap){ VagrantPlugins::HostLinux::Cap::NFS }
+
+    context "with modinfo on PATH" do
+      before do
+        expect(Vagrant::Util::Which).to receive(:which).with("modinfo").and_return("/usr/bin/modinfo")
+      end
+
+      it "should use full path to modinfo" do
+        expect(cap.modinfo_path).to eq("/usr/bin/modinfo")
+      end
+    end
+
+    context "with modinfo at /sbin/modinfo" do
+      before do
+        expect(Vagrant::Util::Which).to receive(:which).with("modinfo").and_return(nil)
+        expect(File).to receive(:file?).with("/sbin/modinfo").and_return(true)
+      end
+
+      it "should use /sbin/modinfo" do
+        expect(cap.modinfo_path).to eq("/sbin/modinfo")
+      end
+    end
+
+    context "modinfo not found" do
+      before do
+        expect(Vagrant::Util::Which).to receive(:which).with("modinfo").and_return(nil)
+        expect(File).to receive(:file?).with("/sbin/modinfo").and_return(false)
+      end
+
+      it "should use modinfo" do
+        expect(cap.modinfo_path).to eq("modinfo")
+      end
+    end
+
+    context "with cached value for modinfo_path" do
+      before do
+        cap.instance_variable_set(:@_modinfo_path, "/usr/local/bin/modinfo")
+      end
+
+      it "should use cached value" do
+        expect(cap.modinfo_path).to eq("/usr/local/bin/modinfo")
+      end
+    end
+  end
 end