diff --git a/fwprovider/ha/resource_hagroup.go b/fwprovider/ha/resource_hagroup.go
index 20981a5eb..6fa6344ef 100644
--- a/fwprovider/ha/resource_hagroup.go
+++ b/fwprovider/ha/resource_hagroup.go
@@ -70,7 +70,7 @@ func (r *hagroupResource) Schema(
 				Required:    true,
 				Validators: []validator.String{
 					stringvalidator.RegexMatches(
-						regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9\-_\.]*[a-zA-Z0-9]$`),
+						regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9\-_.]*[a-zA-Z0-9]$`),
 						"must start with a letter, end with a letter or number, be composed of "+
 							"letters, numbers, '-', '_' and '.', and must be at least 2 characters long",
 					),
diff --git a/fwprovider/ha/resource_haresource.go b/fwprovider/ha/resource_haresource.go
index 1616a0fbb..58629f82e 100644
--- a/fwprovider/ha/resource_haresource.go
+++ b/fwprovider/ha/resource_haresource.go
@@ -110,7 +110,7 @@ func (r *haResourceResource) Schema(
 				Optional:    true,
 				Validators: []validator.String{
 					stringvalidator.RegexMatches(
-						regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9\-_\.]*[a-zA-Z0-9]$`),
+						regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9\-_.]*[a-zA-Z0-9]$`),
 						"must start with a letter, end with a letter or number, be composed of "+
 							"letters, numbers, '-', '_' and '.', and must be at least 2 characters long",
 					),
diff --git a/fwprovider/test/resource_file_test.go b/fwprovider/test/resource_file_test.go
index b3da80b73..62bc54889 100644
--- a/fwprovider/test/resource_file_test.go
+++ b/fwprovider/test/resource_file_test.go
@@ -248,7 +248,9 @@ func uploadSnippetFile(t *testing.T, fileName string) {
 	f, err := os.Open(fileName)
 	require.NoError(t, err)
 
-	defer f.Close()
+	defer func(f *os.File) {
+		_ = f.Close()
+	}(f)
 
 	fname := filepath.Base(fileName)
 	err = sshClient.NodeStreamUpload(context.Background(), "pve", "/var/lib/vz/",
@@ -269,7 +271,9 @@ func createFile(t *testing.T, namePattern string, content string) *os.File {
 	_, err = f.WriteString(content)
 	require.NoError(t, err)
 
-	defer f.Close()
+	defer func(f *os.File) {
+		_ = f.Close()
+	}(f)
 
 	t.Cleanup(func() {
 		_ = os.Remove(f.Name())
diff --git a/proxmox/nodes/vms/custom_vga_device.go b/proxmox/nodes/vms/custom_vga_device.go
index 2e11ab72c..23963adef 100644
--- a/proxmox/nodes/vms/custom_vga_device.go
+++ b/proxmox/nodes/vms/custom_vga_device.go
@@ -22,7 +22,7 @@ type CustomVGADevice struct {
 }
 
 // EncodeValues converts a CustomVGADevice struct to a URL value.
-func (r CustomVGADevice) EncodeValues(key string, v *url.Values) error {
+func (r *CustomVGADevice) EncodeValues(key string, v *url.Values) error {
 	var values []string
 
 	if r.Clipboard != nil {
diff --git a/proxmoxtf/resource/validators/file.go b/proxmoxtf/resource/validators/file.go
index 6b016176a..c631e2065 100644
--- a/proxmoxtf/resource/validators/file.go
+++ b/proxmoxtf/resource/validators/file.go
@@ -50,7 +50,7 @@ func FileID() schema.SchemaValidateDiagFunc {
 		}
 
 		if v != "" {
-			r := regexp.MustCompile(`^(?i)[a-z\d\-_\.]+:([a-z\d\-_]+/)?.+$`)
+			r := regexp.MustCompile(`^(?i)[a-z\d\-_.]+:([a-z\d\-_]+/)?.+$`)
 			ok := r.MatchString(v)
 
 			if !ok {
diff --git a/proxmoxtf/resource/vm/vm.go b/proxmoxtf/resource/vm/vm.go
index e1e514960..e813e1722 100644
--- a/proxmoxtf/resource/vm/vm.go
+++ b/proxmoxtf/resource/vm/vm.go
@@ -89,7 +89,6 @@ const (
 	dvInitializationNetworkDataFileID   = ""
 	dvInitializationMetaDataFileID      = ""
 	dvInitializationType                = ""
-	dvInitializationUpgrade             = true
 	dvKeyboardLayout                    = "en-us"
 	dvKVMArguments                      = ""
 	dvMachineType                       = ""
@@ -1513,16 +1512,6 @@ func VM() *schema.Resource {
 	}
 }
 
-// ConvertToStringSlice helps convert interface slice to string slice.
-func ConvertToStringSlice(interfaceSlice []interface{}) []string {
-	resultSlice := []string{}
-	for _, val := range interfaceSlice {
-		resultSlice = append(resultSlice, val.(string))
-	}
-
-	return resultSlice
-}
-
 func vmCreate(ctx context.Context, d *schema.ResourceData, m interface{}) diag.Diagnostics {
 	clone := d.Get(mkClone).([]interface{})
 
@@ -2873,7 +2862,7 @@ func vmGetCloudInitConfig(d *schema.ResourceData) *vms.CustomCloudInitConfig {
 		deprecatedServer := initializationDNSBlock[mkInitializationDNSServer].(string)
 
 		if len(servers) > 0 {
-			nameserver := strings.Join(ConvertToStringSlice(servers), " ")
+			nameserver := strings.Join(utils.ConvertToStringSlice(servers), " ")
 
 			initializationConfig.Nameserver = &nameserver
 		} else if deprecatedServer != "" {