Code to fix the systemd instatiated services when enabled/disabled vi…

…a ignition

internal/exec/stages/files/units.go

@@ -17,37 +17,96 @@ package files
 import (
 	"fmt"
 	"path/filepath"
+	"strconv"
 	"strings"
 
+	"github.com/coreos/go-systemd/dbus"
 	"github.com/coreos/ignition/v2/config/v3_1_experimental/types"
 	"github.com/coreos/ignition/v2/internal/distro"
 	"github.com/coreos/ignition/v2/internal/exec/util"
 )
 
+type Preset struct {
+	unit            string
+	enabled         bool
+	instantiateable bool
+	instances       []string
+}
+
+// warnOnOldSystemdVersion checks the version of Systemd
+// in a given system.
+func (s *stage) warnOnOldSystemdVersion() error {
+	var systemdVersion string
+	var begin, end int
+	conn, err := dbus.New()
+	if err != nil {
+		return err
+	}
+	version, err := conn.GetManagerProperty("Version")
+	if err != nil {
+		return err
+	}
+	// Handle different systemd versioning schemes that are being returned.
+	// for e.g:
+	// - Fedora 31: `v243.5-1.fc31`
+	// - RHEL 8: `239`
+	if strings.HasPrefix(version, "v") {
+		begin = 1
+
+	} else {
+		begin = 0
+	}
+	end = strings.Index(version, ".")
+	if end == -1 {
+		end = len(version)
+	}
+	systemdVersion = version[begin:end]
+	if value, err := strconv.Atoi(systemdVersion); err == nil {
+		if value < 240 {
+			if err := s.Logger.Warning("The version of systemd (%q) is less than 240. Enabling/disabling instantiated units may not work. See https://github.com/coreos/ignition/issues/586 for more information.", systemdVersion); err != nil {
+				return err
+			}
+		}
+	} else {
+		return err
+	}
+	return nil
+}
+
 // createUnits creates the units listed under systemd.units.
 func (s *stage) createUnits(config types.Config) error {
-	enabledOneUnit := false
+	presets := make(map[string]*Preset)
 	for _, unit := range config.Systemd.Units {
 		if err := s.writeSystemdUnit(unit, false); err != nil {
 			return err
 		}
 		if unit.Enabled != nil {
 			if *unit.Enabled {
-				if err := s.Logger.LogOp(
-					func() error { return s.EnableUnit(unit) },
-					"enabling unit %q", unit.Name,
-				); err != nil {
-					return err
+				if strings.Contains(unit.Name, "@") {
+					unitName, instance := parseInstanceUnit(unit)
+					if len(instance) > 0 {
+						if _, ok := presets[unitName]; ok {
+							presets[unitName].instances = append(presets[unitName].instances, instance)
+						} else {
+							presets[unitName] = &Preset{unitName, true, true, []string{instance}}
+						}
+					}
+
+				} else {
+					presets[unit.Name] = &Preset{unit.Name, true, false, []string{}}
 				}
+
 			} else {
-				if err := s.Logger.LogOp(
-					func() error { return s.DisableUnit(unit) },
-					"disabling unit %q", unit.Name,
-				); err != nil {
-					return err
+				if strings.Contains(unit.Name, "@") {
+					unitName, instance := parseInstanceUnit(unit)
+					if len(instance) > 0 {
+						presets[unitName] = &Preset{unitName, false, true, []string{instance}}
+					}
+
+				} else {
+					presets[unit.Name] = &Preset{unit.Name, false, false, []string{}}
 				}
 			}
-			enabledOneUnit = true
 		}
 		if unit.Mask != nil && *unit.Mask {
 			relabelpath := ""
@@ -65,9 +124,69 @@ func (s *stage) createUnits(config types.Config) error {
 		}
 	}
 	// and relabel the preset file itself if we enabled/disabled something
-	if enabledOneUnit {
-		s.relabel(util.PresetPath)
+	if len(presets) != 0 {
+		if err := s.createSystemdPresetFile(presets); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// parseInstanceUnit is a helper function to extract the name
+// and coresponding instances for a given instantiated unit.
+func parseInstanceUnit(unit types.Unit) (string, string) {
+	at := strings.Index(unit.Name, "@")
+	dot := strings.Index(unit.Name, ".")
+	instance := unit.Name[at+1 : dot]
+	serviceInstance := unit.Name[0:at+1] + unit.Name[dot:len(unit.Name)]
+
+	return serviceInstance, instance
+}
+
+// createSystemdPresetFile creates the presetfile for enabled/disabled
+// instantiated/systemd units.
+func (s *stage) createSystemdPresetFile(presets map[string]*Preset) error {
+	var enableUnitString, disableUnitString string
+	hasInstanceUnit := false
+	for _, value := range presets {
+		if value.instantiateable {
+			hasInstanceUnit = true
+		}
+		if value.enabled {
+			if value.instantiateable {
+				enableUnitString = value.unit + " " + strings.Join(value.instances, " ")
+			} else {
+				enableUnitString = value.unit
+			}
+			if err := s.Logger.LogOp(
+				func() error { return s.EnableUnit(enableUnitString) },
+				"enabling unit %q", enableUnitString,
+			); err != nil {
+				return err
+			}
+		} else {
+			if value.instantiateable {
+				disableUnitString = value.unit + " " + strings.Join(value.instances, " ")
+			} else {
+				disableUnitString = value.unit
+			}
+			if err := s.Logger.LogOp(
+				func() error { return s.DisableUnit(disableUnitString) },
+				"disabling unit %q", disableUnitString,
+			); err != nil {
+				return err
+			}
+		}
+	}
+
+	// Print the warning if there's an instantiated unit present under
+	// the systemd units and the version of systemd in a given system
+	// is less than 240.
+	if hasInstanceUnit {
+		s.warnOnOldSystemdVersion()
 	}
+	s.relabel(util.PresetPath)
 	return nil
 }
 

internal/exec/util/unit.go

@@ -110,8 +110,8 @@ func (ut Util) MaskUnit(unit types.Unit) (string, error) {
 	return filepath.Join("/", SystemdUnitsPath(), unit.Name), nil
 }
 
-func (ut Util) EnableUnit(unit types.Unit) error {
-	return ut.appendLineToPreset(fmt.Sprintf("enable %s", unit.Name))
+func (ut Util) EnableUnit(enabledUnit string) error {
+	return ut.appendLineToPreset(fmt.Sprintf("enable %s", enabledUnit))
 }
 
 // presets link in /etc, which doesn't make sense for runtime units
@@ -145,8 +145,8 @@ func (ut Util) EnableRuntimeUnit(unit types.Unit, target string) error {
 	return ut.WriteLink(link)
 }
 
-func (ut Util) DisableUnit(unit types.Unit) error {
-	return ut.appendLineToPreset(fmt.Sprintf("disable %s", unit.Name))
+func (ut Util) DisableUnit(disabledUnit string) error {
+	return ut.appendLineToPreset(fmt.Sprintf("disable %s", disabledUnit))
 }
 
 func (ut Util) appendLineToPreset(data string) error {