diff --git a/fork/golang/expansion/expand.go b/fork/golang/expansion/expand.go
index 6bf0ea8ce09..32bf62e9875 100644
--- a/fork/golang/expansion/expand.go
+++ b/fork/golang/expansion/expand.go
@@ -2,17 +2,20 @@ package expansion
 
 import (
 	"bytes"
+	"unicode"
 )
 
 const (
-	operator        = '$'
-	referenceOpener = '('
-	referenceCloser = ')'
+	operator             = '$'
+	referenceCurlyOpener = '{'
+	referenceCurlyCloser = '}'
+	referenceParenOpener = '('
+	referenceParenCloser = ')'
 )
 
 // syntaxWrap returns the input string wrapped by the expansion syntax.
 func syntaxWrap(input string) string {
-	return string(operator) + string(referenceOpener) + input + string(referenceCloser)
+	return string(operator) + string(referenceParenOpener) + input + string(referenceParenCloser)
 }
 
 // MappingFuncFor returns a mapping function for use with Expand that
@@ -83,20 +86,41 @@ func tryReadVariableName(input string) (string, bool, int) {
 	case operator:
 		// Escaped operator; return it.
 		return input[0:1], false, 1
-	case referenceOpener:
+	case referenceParenOpener:
 		// Scan to expression closer
 		for i := 1; i < len(input); i++ {
-			if input[i] == referenceCloser {
+			if input[i] == referenceParenCloser {
 				return input[1:i], true, i + 1
 			}
 		}
 
 		// Incomplete reference; return it.
-		return string(operator) + string(referenceOpener), false, 1
+		return string(operator) + string(referenceParenOpener), false, 1
+	case referenceCurlyOpener:
+		// Scan to expression closer
+		for i := 1; i < len(input); i++ {
+			if input[i] == referenceCurlyCloser {
+				return input[1:i], true, i + 1
+			}
+		}
+
+		// Incomplete reference; return it.
+		return string(operator) + string(referenceParenOpener), false, 1
 	default:
 		// Not the beginning of an expression, ie, an operator
 		// that doesn't begin an expression.  Return the operator
 		// and the first rune in the string.
-		return (string(operator) + string(input[0])), false, 1
+		var variableName string
+		var i int
+		for i = 0; i < len(input); i++ {
+			if !unicode.IsLetter(rune(input[i])) && !unicode.IsDigit(rune(input[i])) && input[i] != '_' {
+				break
+			}
+			variableName += string(input[i])
+		}
+		if len(variableName) > 0 {
+			return variableName, true, i
+		}
+		return string(operator) + string(input[0]), false, 1
 	}
 }
diff --git a/pkg/guest/guest_test.go b/pkg/guest/guest_test.go
index d63e9e3fff8..638c187891b 100644
--- a/pkg/guest/guest_test.go
+++ b/pkg/guest/guest_test.go
@@ -135,3 +135,223 @@ func TestDefault_getGuestCmd(t *testing.T) {
 		})
 	}
 }
+
+func TestDefault_getGuestCmd_dollarBraceVariable(t *testing.T) {
+	shell := func(cName, containerName, cmd string) string {
+		return fmt.Sprintf(constants.CdAndExecCmd, constants.GetAppWorkDir(cName, containerName), cmd)
+	}
+	type fields struct {
+	}
+	type args struct {
+		envs    map[string]string
+		cluster *v2.Cluster
+		mounts  []v2.MountImage
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   []string
+	}{
+		{
+			name:   "default",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=${IFACE} bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "cccc"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=cccc bash ovn-install.sh")},
+		},
+
+		{
+			name:   "default-env",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"${IFACE}\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"eth.*|en.*\" bash ovn-install.sh")},
+		},
+		{
+			name:   "default-env-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"${IFACE}\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"default\" bash ovn-install.sh")},
+		},
+		{
+			name:   "default-cmd-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: []string{"IFACE=\"${IFACE}\" sh ovn-install.sh"}}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"${IFACE}\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"default\" sh ovn-install.sh")},
+		},
+		{
+			name:   "default-entrypoint-cmd-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: []string{"IFACE=\"${IFACE}\" sh ovn-install.sh"}}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"${IFACE}\" bash ovn-install.sh"},
+						Entrypoint: []string{"AA=${IFACE}"},
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "AA=default"), shell("", "", "IFACE=\"default\" sh ovn-install.sh")},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			for i := range tt.args.mounts {
+				if got := formalizeImageCommands(tt.args.cluster, i, tt.args.mounts[i], tt.args.envs); !reflect.DeepEqual(got, tt.want) {
+					t.Errorf("getGuestCmd() = %v, want %v", got, tt.want)
+				}
+			}
+		})
+	}
+}
+
+func TestDefault_getGuestCmd_dollarVariable(t *testing.T) {
+	shell := func(cName, containerName, cmd string) string {
+		return fmt.Sprintf(constants.CdAndExecCmd, constants.GetAppWorkDir(cName, containerName), cmd)
+	}
+	type fields struct {
+	}
+	type args struct {
+		envs    map[string]string
+		cluster *v2.Cluster
+		mounts  []v2.MountImage
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   []string
+	}{
+		{
+			name:   "default",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=$IFACE bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "cccc"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=cccc bash ovn-install.sh")},
+		},
+
+		{
+			name:   "default-env",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"$IFACE\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"eth.*|en.*\" bash ovn-install.sh")},
+		},
+		{
+			name:   "default-env-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: nil}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"$IFACE\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"default\" bash ovn-install.sh")},
+		},
+		{
+			name:   "default-cmd-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: []string{"IFACE=\"$IFACE\" sh ovn-install.sh"}}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"$IFACE\" bash ovn-install.sh"},
+						Entrypoint: nil,
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "IFACE=\"default\" sh ovn-install.sh")},
+		},
+		{
+			name:   "default-entrypoint-cmd-override",
+			fields: fields{},
+			args: args{
+				envs:    map[string]string{"IFACE": "default"},
+				cluster: &v2.Cluster{Spec: v2.ClusterSpec{Command: []string{"IFACE=\"$IFACE\" sh ovn-install.sh"}}},
+				mounts: []v2.MountImage{
+					{
+						Cmd:        []string{"IFACE=\"$IFACE\" bash ovn-install.sh"},
+						Entrypoint: []string{"AA=$IFACE"},
+						Env:        map[string]string{"IFACE": "eth.*|en.*"},
+					},
+				},
+			},
+			want: []string{shell("", "", "AA=default"), shell("", "", "IFACE=\"default\" sh ovn-install.sh")},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			for i := range tt.args.mounts {
+				if got := formalizeImageCommands(tt.args.cluster, i, tt.args.mounts[i], tt.args.envs); !reflect.DeepEqual(got, tt.want) {
+					t.Errorf("getGuestCmd() = %v, want %v", got, tt.want)
+				}
+			}
+		})
+	}
+}