diff --git a/pkg/phase/executors/container.go b/pkg/phase/executors/container.go
index f5ede4f32..beafd8d84 100644
--- a/pkg/phase/executors/container.go
+++ b/pkg/phase/executors/container.go
@@ -35,11 +35,6 @@ import (
 	"opendev.org/airship/airshipctl/pkg/phase/ifc"
 )
 
-const (
-	// yamlSeparator uses to separate yaml files
-	yamlSeparator = "---\n"
-)
-
 var _ ifc.Executor = &ContainerExecutor{}
 
 // ContainerExecutor contains resources for generic container executor
@@ -130,23 +125,14 @@ func (c *ContainerExecutor) Run(evtCh chan events.Event, opts ifc.RunOptions) {
 
 // SetInput sets input for function
 func (c *ContainerExecutor) SetInput(evtCh chan events.Event) {
-	docs, err := c.ExecutorBundle.GetAllDocuments()
+	buf := &bytes.Buffer{}
+	err := c.ExecutorBundle.Write(buf)
 	if err != nil {
 		handleError(evtCh, err)
 		return
 	}
 
-	docsBytes := make([]byte, 0)
-	for _, doc := range docs {
-		data, err := doc.AsYAML()
-		if err != nil {
-			handleError(evtCh, err)
-			return
-		}
-		docsBytes = append(docsBytes, []byte(yamlSeparator)...)
-		docsBytes = append(docsBytes, data...)
-	}
-	c.RunFns.Input = bytes.NewReader(docsBytes)
+	c.RunFns.Input = buf
 }
 
 // PrepareFunctions prepares data for function
diff --git a/pkg/phase/executors/container_test.go b/pkg/phase/executors/container_test.go
index 6e0df1aca..075bd504c 100644
--- a/pkg/phase/executors/container_test.go
+++ b/pkg/phase/executors/container_test.go
@@ -32,6 +32,7 @@ import (
 	"opendev.org/airship/airshipctl/pkg/phase"
 	"opendev.org/airship/airshipctl/pkg/phase/executors"
 	"opendev.org/airship/airshipctl/pkg/phase/ifc"
+	yaml_util "opendev.org/airship/airshipctl/pkg/util/yaml"
 )
 
 const (
@@ -107,7 +108,6 @@ metadata:
   name: master-0-bmc-secret
 type: Opaque
 `
-	yamlSeparator = "---\n"
 )
 
 func TestRegisterContainerExecutor(t *testing.T) {
@@ -161,9 +161,12 @@ func TestSetInputSingleDocument(t *testing.T) {
 	require.NoError(t, err)
 	docBytes, err := doc.AsYAML()
 	require.NoError(t, err)
-	docBytes = append([]byte(yamlSeparator), docBytes...)
+	buf := &bytes.Buffer{}
+	buf.Write([]byte(yaml_util.DashYamlSeparator))
+	buf.Write(docBytes)
+	buf.Write([]byte(yaml_util.DotYamlSeparator))
 
-	assert.Equal(t, bytes.NewReader(docBytes), e.RunFns.Input)
+	assert.Equal(t, buf, e.RunFns.Input)
 }
 
 func TestSetInputManyDocuments(t *testing.T) {
@@ -192,16 +195,21 @@ func TestSetInputManyDocuments(t *testing.T) {
 	require.NoError(t, err)
 	docSecondBytes, err := docSecond.AsYAML()
 	require.NoError(t, err)
-	docBytes := append([]byte(yamlSeparator), docSecondBytes...)
+
+	buf := &bytes.Buffer{}
+	buf.Write([]byte(yaml_util.DashYamlSeparator))
+	buf.Write(docSecondBytes)
+	buf.Write([]byte(yaml_util.DotYamlSeparator))
 
 	docFirst, err := document.NewDocumentFromBytes([]byte(firstDocInput))
 	require.NoError(t, err)
 	docFirstBytes, err := docFirst.AsYAML()
 	require.NoError(t, err)
-	docBytes = append(docBytes, []byte(yamlSeparator)...)
-	docBytes = append(docBytes, docFirstBytes...)
+	buf.Write([]byte(yaml_util.DashYamlSeparator))
+	buf.Write(docFirstBytes)
+	buf.Write([]byte(yaml_util.DotYamlSeparator))
 
-	assert.Equal(t, bytes.NewReader(docBytes), e.RunFns.Input)
+	assert.Equal(t, buf, e.RunFns.Input)
 }
 
 func TestPrepareFunctions(t *testing.T) {