cherry-pick: more sysv

Merge in DNS/adguard-home from 4480-sysv-again to master

Updates #4480.

Squashed commit of the following:

commit 263fa05ab19de95b18fb07f6c89e4b9a1b24657b
Merge: 360a6468 d3f39b0a
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jun 14 13:36:15 2022 +0300

    Merge branch 'master' into 4480-sysv-again

commit 360a646833ca9e0e01cb6d085e70b898a30dc2d0
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jun 9 18:15:41 2022 +0300

    home: rename linux file

commit c3032533b7e00136c25d15a4ad771bb8a9c13e31
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jun 9 18:06:25 2022 +0300

    home: imp code

commit 2381c4a6ab4f6dca88123ff7b0a92f2cf9a420a8
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Thu Jun 9 17:48:22 2022 +0300

    home: wrap sysv service

internal/home/service_linux.go

@@ -0,0 +1,76 @@
+//go:build linux
+// +build linux
+
+package home
+
+import (
+	"github.com/AdguardTeam/AdGuardHome/internal/aghos"
+	"github.com/kardianos/service"
+)
+
+func chooseSystem() {
+	if sys := service.ChosenSystem(); sys.String() == "unix-systemv" {
+		service.ChooseSystem(sysvSystem{System: sys})
+	}
+}
+
+// sysvSystem is a wrapper for service.System that wraps the service.Service
+// while creating a new one.
+//
+// TODO(e.burkov):  File a PR to github.com/kardianos/service.
+type sysvSystem struct {
+	// System is expected to have an unexported type
+	// *service.linuxSystemService.
+	service.System
+}
+
+// New returns a wrapped service.Service.
+func (sys sysvSystem) New(i service.Interface, c *service.Config) (s service.Service, err error) {
+	s, err = sys.System.New(i, c)
+	if err != nil {
+		return s, err
+	}
+
+	return sysvService{
+		Service: s,
+		name:    c.Name,
+	}, nil
+}
+
+// sysvService is a wrapper for a service.Service that also calls update-rc.d in
+// a proper way on installing and uninstalling.
+type sysvService struct {
+	// Service is expected to have an unexported type *service.sysv.
+	service.Service
+	// name stores the name of the service to call updating script with it.
+	name string
+}
+
+// Install wraps service.Service.Install call with calling the updating script.
+func (svc sysvService) Install() (err error) {
+	err = svc.Service.Install()
+	if err != nil {
+		// Don't wrap an error since it's informative enough as is.
+		return err
+	}
+
+	_, _, err = aghos.RunCommand("update-rc.d", svc.name, "defaults")
+
+	// Don't wrap an error since it's informative enough as is.
+	return err
+}
+
+// Uninstall wraps service.Service.Uninstall call with calling the updating
+// script.
+func (svc sysvService) Uninstall() (err error) {
+	err = svc.Service.Uninstall()
+	if err != nil {
+		// Don't wrap an error since it's informative enough as is.
+		return err
+	}
+
+	_, _, err = aghos.RunCommand("update-rc.d", svc.name, "remove")
+
+	// Don't wrap an error since it's informative enough as is.
+	return err
+}

internal/home/service_others.go

@@ -1,6 +1,8 @@
-//go:build !openbsd
-// +build !openbsd
+//go:build !(openbsd || linux)
+// +build !openbsd,!linux
 
 package home
 
+// chooseSystem checks the current system detected and substitutes it with local
+// implementation if needed.
 func chooseSystem() {}