chore(*): split out unit processing from config.Apply

system/unit.go

@@ -0,0 +1,67 @@
+package system
+
+import (
+	"fmt"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+// Name for drop-in service configuration files created by cloudconfig
+const cloudConfigDropIn = "20-cloudinit.conf"
+
+type UnitManager interface {
+	PlaceUnit(unit *Unit, dst string) error
+	EnableUnitFile(unit string, runtime bool) error
+	RunUnitCommand(command, unit string) (string, error)
+	DaemonReload() error
+	MaskUnit(unit *Unit) error
+	UnmaskUnit(unit *Unit) error
+}
+
+type Unit struct {
+	Name    string
+	Mask    bool
+	Enable  bool
+	Runtime bool
+	Content string
+	Command string
+
+	// For drop-in units, a cloudinit.conf is generated.
+	// This is currently unbound in YAML (and hence unsettable in cloud-config files)
+	// until the correct behaviour for multiple drop-in units is determined.
+	DropIn bool `yaml:"-"`
+}
+
+func (u *Unit) Type() string {
+	ext := filepath.Ext(u.Name)
+	return strings.TrimLeft(ext, ".")
+}
+
+func (u *Unit) Group() (group string) {
+	t := u.Type()
+	if t == "network" || t == "netdev" || t == "link" {
+		group = "network"
+	} else {
+		group = "system"
+	}
+	return
+}
+
+type Script []byte
+
+// Destination builds the appropriate absolute file path for
+// the Unit. The root argument indicates the effective base
+// directory of the system (similar to a chroot).
+func (u *Unit) Destination(root string) string {
+	dir := "etc"
+	if u.Runtime {
+		dir = "run"
+	}
+
+	if u.DropIn {
+		return path.Join(root, dir, "systemd", u.Group(), fmt.Sprintf("%s.d", u.Name), cloudConfigDropIn)
+	} else {
+		return path.Join(root, dir, "systemd", u.Group(), u.Name)
+	}
+}