Add systemd utility package

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/systemd/systemd.go

@@ -0,0 +1,100 @@
+package systemd
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"text/template"
+
+	execute "github.com/alexellis/go-execute/pkg/v1"
+)
+
+func Enable(unit string) error {
+	task := execute.ExecTask{Command: "systemctl",
+		Args:        []string{"enable", unit},
+		StreamStdio: false,
+	}
+
+	res, err := task.Execute()
+	if err != nil {
+		return err
+	}
+
+	if res.ExitCode != 0 {
+		return fmt.Errorf("error executing task %s %v, stderr: %s", task.Command, task.Args, res.Stderr)
+	}
+
+	return nil
+}
+
+func Start(unit string) error {
+	task := execute.ExecTask{Command: "systemctl",
+		Args:        []string{"start", unit},
+		StreamStdio: false,
+	}
+
+	res, err := task.Execute()
+	if err != nil {
+		return err
+	}
+
+	if res.ExitCode != 0 {
+		return fmt.Errorf("error executing task %s %v, stderr: %s", task.Command, task.Args, res.Stderr)
+	}
+
+	return nil
+}
+
+func DaemonReload() error {
+	task := execute.ExecTask{Command: "systemctl",
+		Args:        []string{"daemon-reload"},
+		StreamStdio: false,
+	}
+
+	res, err := task.Execute()
+	if err != nil {
+		return err
+	}
+
+	if res.ExitCode != 0 {
+		return fmt.Errorf("error executing task %s %v, stderr: %s", task.Command, task.Args, res.Stderr)
+	}
+
+	return nil
+}
+
+func InstallUnit(name string) error {
+
+	tmpl, err := template.ParseFiles("./hack/" + name + ".service")
+
+	wd, _ := os.Getwd()
+	var tpl bytes.Buffer
+	userData := struct {
+		Cwd string
+	}{
+		Cwd: wd,
+	}
+
+	err = tmpl.Execute(&tpl, userData)
+	if err != nil {
+		return err
+	}
+
+	err = writeUnit(name+".service", tpl.Bytes())
+
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func writeUnit(name string, data []byte) error {
+	f, err := os.Create(filepath.Join("/lib/systemd/system", name))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	_, err = f.Write(data)
+	return err
+}