// InstantiatedPrepareAppUnitName returns the systemd service unit name for prepare-app
// instantiated for the given root
func InstantiatedPrepareAppUnitName(imageID types.Hash) string {
	// Naming respecting escaping rules, see systemd.unit(5) and systemd-escape(1)
	escaped_root := common.RelAppRootfsPath(imageID)
	escaped_root = strings.Replace(escaped_root, "-", "\\x2d", -1)
	escaped_root = strings.Replace(escaped_root, "/", "-", -1)
	return "[email protected]" + escaped_root + ".service"
}

// AppReaperUnit writes an app reaper service unit for the given app in the given path using the given unit options.
func (uw *UnitWriter) AppReaperUnit(appName types.ACName, binPath string, opts ...*unit.UnitOption) {
	if uw.err != nil {
		return
	}

	opts = append(opts, []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", fmt.Sprintf("%s Reaper", appName)),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "StopWhenUnneeded", "yes"),
		unit.NewUnitOption("Unit", "Before", "halt.target"),
		unit.NewUnitOption("Unit", "Conflicts", "exit.target"),
		unit.NewUnitOption("Unit", "Conflicts", "halt.target"),
		unit.NewUnitOption("Unit", "Conflicts", "poweroff.target"),
		unit.NewUnitOption("Service", "RemainAfterExit", "yes"),
		unit.NewUnitOption("Service", "ExecStop", fmt.Sprintf(
			"/reaper.sh \"%s\" \"%s\" \"%s\"",
			appName,
			common.RelAppRootfsPath(appName),
			binPath,
		)),
	}...)

	uw.WriteUnit(
		ServiceUnitPath(uw.p.Root, types.ACName(fmt.Sprintf("reaper-%s", appName))),
		fmt.Sprintf("failed to write app %q reaper service", appName),
		opts...,
	)
}

// AppToSystemdMountUnits prepare bind mount unit for empty or host kind mounting
// between stage1 rootfs and chrooted filesystem for application
func AppToSystemdMountUnits(root string, appName types.ACName, mountPoints []types.MountPoint, unitsDir string) error {

	for _, mountPoint := range mountPoints {

		name := mountPoint.Name.String()
		// source relative to stage1 rootfs to relative pod root
		whatPath := filepath.Join(stage1MntDir, name)
		whatFullPath := filepath.Join(root, whatPath)

		// destination relative to stage1 rootfs and relative to pod root
		wherePath := filepath.Join(common.RelAppRootfsPath(appName), mountPoint.Path)
		whereFullPath := filepath.Join(root, wherePath)

		// readOnly
		mountOptions := "bind"
		if mountPoint.ReadOnly {
			mountOptions += ",ro"
		}

		// assertion to make sure that "what" exists (created earlier by podToSystemdHostMountUnits)
		log.Printf("checking required source path: %q", whatFullPath)
		if _, err := os.Stat(whatFullPath); os.IsNotExist(err) {
			return fmt.Errorf("app requires a volume that is not defined in Pod (try adding --volume=%s,kind=empty)!", name)
		}

		// optionally prepare app directory
		log.Printf("optionally preparing destination path: %q", whereFullPath)
		err := os.MkdirAll(whereFullPath, 0700)
		if err != nil {
			return fmt.Errorf("failed to prepare dir for mountPoint %v: %v", mountPoint.Name, err)
		}

		// install new mount unit for bind mount /mnt/volumeName -> /opt/stage2/{app-id}/rootfs/{{mountPoint.Path}}
		err = installNewMountUnit(
			root,      // where put a mount unit
			whatPath,  // what - stage1 rootfs /mnt/VolumeName
			wherePath, // where - inside chroot app filesystem
			"bind",    // fstype
			mountOptions,
			serviceUnitName(appName),
			unitsDir,
		)
		if err != nil {
			return fmt.Errorf("cannot install new mount unit for app %q: %v", appName.String(), err)
		}

	}
	return nil
}

// generateDeviceAllows generates a DeviceAllow= line for an app.
// To make it work, the path needs to start with "/dev" but the device won't
// exist inside the container. So for a given mount, if the volume is a device
// node, we create a symlink to its target in "/rkt/volumes". Later,
// prepare-app will copy those to "/dev/.rkt/" so that's what we use in the
// DeviceAllow= line.
func generateDeviceAllows(root string, appName types.ACName, mountPoints []types.MountPoint, mounts []mountWrapper, vols map[types.ACName]types.Volume, uidRange *user.UidRange) ([]string, error) {
	var devAllow []string

	rktVolumeLinksPath := filepath.Join(root, "rkt", "volumes")
	if err := os.MkdirAll(rktVolumeLinksPath, 0600); err != nil {
		return nil, err
	}
	if err := user.ShiftFiles([]string{rktVolumeLinksPath}, uidRange); err != nil {
		return nil, err
	}

	for _, m := range mounts {
		v := vols[m.Volume]
		if v.Kind != "host" {
			continue
		}
		if fileutil.IsDeviceNode(v.Source) {
			mode := "r"
			if !IsMountReadOnly(v, mountPoints) {
				mode += "w"
			}

			tgt := filepath.Join(common.RelAppRootfsPath(appName), m.Path)
			// the DeviceAllow= line needs the link path in /dev/.rkt/
			linkRel := filepath.Join("/dev/.rkt", v.Name.String())
			// the real link should be in /rkt/volumes for now
			link := filepath.Join(rktVolumeLinksPath, v.Name.String())

			err := os.Symlink(tgt, link)
			// if the link already exists, we don't need to do anything
			if err != nil && !os.IsExist(err) {
				return nil, err
			}

			devAllow = append(devAllow, linkRel+" "+mode)
		}
	}

	return devAllow, nil
}

// appToSystemd transforms the provided RuntimeApp+ImageManifest into systemd units
func (p *Pod) appToSystemd(ra *schema.RuntimeApp, interactive bool) error {
	name := ra.Name.String()
	id := ra.Image.ID
	app := ra.App

	workDir := "/"
	if app.WorkingDirectory != "" {
		workDir = app.WorkingDirectory
	}

	env := app.Environment
	env.Set("AC_APP_NAME", name)
	env.Set("AC_METADATA_URL", p.MetadataServiceURL)

	if err := p.writeEnvFile(env, id); err != nil {
		return fmt.Errorf("unable to write environment file: %v", err)
	}

	// This is a partial implementation for app.User and app.Group:
	// For now, only numeric ids (and the string "root") are supported.
	var uid, gid int
	var err error
	if app.User == "root" {
		uid = 0
	} else {
		uid, err = strconv.Atoi(app.User)
		if err != nil {
			return fmt.Errorf("non-numerical user id not supported yet")
		}
	}
	if app.Group == "root" {
		gid = 0
	} else {
		gid, err = strconv.Atoi(app.Group)
		if err != nil {
			return fmt.Errorf("non-numerical group id not supported yet")
		}
	}

	execWrap := []string{"/diagexec", common.RelAppRootfsPath(id), workDir, RelEnvFilePath(id), strconv.Itoa(uid), strconv.Itoa(gid)}
	execStart := quoteExec(append(execWrap, app.Exec...))
	opts := []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", name),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "OnFailure", "reaper.service"),
		unit.NewUnitOption("Unit", "Wants", "exit-watcher.service"),
		unit.NewUnitOption("Service", "Restart", "no"),
		unit.NewUnitOption("Service", "ExecStart", execStart),
		unit.NewUnitOption("Service", "User", "0"),
		unit.NewUnitOption("Service", "Group", "0"),
	}

	_, systemdStage1Version, err := p.getFlavor()
	if err != nil {
		return fmt.Errorf("Failed to get stage1 flavor: %v\n", err)
	}

	if interactive {
		opts = append(opts, unit.NewUnitOption("Service", "StandardInput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "tty"))
	} else if systemdSupportsJournalLinking(systemdStage1Version) {
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "journal+console"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "journal+console"))
		opts = append(opts, unit.NewUnitOption("Service", "SyslogIdentifier", filepath.Base(app.Exec[0])))
	}

	for _, eh := range app.EventHandlers {
		var typ string
		switch eh.Name {
		case "pre-start":
			typ = "ExecStartPre"
		case "post-stop":
			typ = "ExecStopPost"
		default:
			return fmt.Errorf("unrecognized eventHandler: %v", eh.Name)
		}
		exec := quoteExec(append(execWrap, eh.Exec...))
		opts = append(opts, unit.NewUnitOption("Service", typ, exec))
	}

	saPorts := []types.Port{}
	for _, p := range app.Ports {
		if p.SocketActivated {
			saPorts = append(saPorts, p)
		}
	}

	for _, i := range app.Isolators {
		switch v := i.Value().(type) {
		case *types.ResourceMemory:
			limit := v.Limit().String()
			opts, err = cgroup.MaybeAddIsolator(opts, "memory", limit)
			if err != nil {
				return err
			}
		case *types.ResourceCPU:
			limit := v.Limit().String()
			opts, err = cgroup.MaybeAddIsolator(opts, "cpu", limit)
//.........这里部分代码省略.........

// protectKernelTunables restricts access to some security-sensitive paths under
// /proc and /sys. Entries are either hidden or just made read-only to app.
// This protection is enabled by default.
func protectKernelTunables(opts []*unit.UnitOption, appName types.ACName, systemdVersion int) []*unit.UnitOption {
	roPaths := []string{
		"/proc/bus/",
		"/proc/sys/kernel/core_pattern",
		"/proc/sys/kernel/modprobe",
		"/proc/sys/vm/panic_on_oom",
		"/proc/sysrq-trigger",
		"/sys/block/",
		"/sys/bus/",
		"/sys/class/",
		"/sys/dev/",
		"/sys/devices/",
		"/sys/kernel/",
	}
	hiddenDirs := []string{
		"/sys/firmware/",
		"/sys/fs/",
		"/sys/hypervisor/",
		"/sys/module/",
		"/sys/power/",
	}
	hiddenPaths := []string{
		"/proc/config.gz",
		"/proc/kallsyms",
		"/proc/sched_debug",
		"/proc/kcore",
		"/proc/kmem",
		"/proc/mem",
	}

	// Paths prefixed with "-" are ignored if they do not exist:
	// https://www.freedesktop.org/software/systemd/man/systemd.exec.html#ReadWriteDirectories=
	for _, p := range roPaths {
		opts = append(opts, unit.NewUnitOption("Service", "ReadOnlyDirectories", fmt.Sprintf("-%s", filepath.Join(common.RelAppRootfsPath(appName), p))))
	}
	for _, p := range hiddenDirs {
		opts = append(opts, unit.NewUnitOption("Service", "InaccessibleDirectories", fmt.Sprintf("-%s", filepath.Join(common.RelAppRootfsPath(appName), p))))
	}
	if systemdVersion >= 231 {
		for _, p := range hiddenPaths {
			opts = append(opts, unit.NewUnitOption("Service", "InaccessiblePaths", fmt.Sprintf("-%s", filepath.Join(common.RelAppRootfsPath(appName), p))))
		}
	}
	if systemdVersion >= 233 {
		opts = append(opts, unit.NewUnitOption("Service", "ProtectKernelTunables", "true"))
	}

	return opts
}

// appToNspawnArgs transforms the given app manifest, with the given associated
// app name, into a subset of applicable systemd-nspawn argument
func appToNspawnArgs(p *stage1commontypes.Pod, ra *schema.RuntimeApp) ([]string, error) {
	var args []string
	appName := ra.Name
	app := ra.App

	sharedVolPath, err := common.CreateSharedVolumesPath(p.Root)
	if err != nil {
		return nil, err
	}

	vols := make(map[types.ACName]types.Volume)
	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
	}

	imageManifest := p.Images[appName.String()]
	mounts, err := GenerateMounts(ra, p.Manifest.Volumes, ConvertedFromDocker(imageManifest))
	if err != nil {
		return nil, errwrap.Wrap(fmt.Errorf("could not generate app %q mounts", appName), err)
	}
	for _, m := range mounts {
		shPath := filepath.Join(sharedVolPath, m.Volume.Name.String())

		absRoot, err := filepath.Abs(p.Root) // Absolute path to the pod's rootfs.
		if err != nil {
			return nil, errwrap.Wrap(errors.New("could not get pod's root absolute path"), err)
		}

		appRootfs := common.AppRootfsPath(absRoot, appName)

		// Evaluate symlinks within the app's rootfs. This is needed because symlinks
		// within the container can be absolute, which will, of course, be wrong in our ns.
		// Systemd also gets this wrong, see https://github.com/systemd/systemd/issues/2860
		// When the above issue is fixed, we can pass the un-evaluated path to --bind instead.
		mntPath, err := EvaluateSymlinksInsideApp(appRootfs, m.Mount.Path)
		if err != nil {
			return nil, errwrap.Wrap(fmt.Errorf("could not evaluate path %v", m.Mount.Path), err)
		}
		mntAbsPath := filepath.Join(appRootfs, mntPath)

		if err := PrepareMountpoints(shPath, mntAbsPath, &m.Volume, m.DockerImplicit); err != nil {
			return nil, err
		}

		opt := make([]string, 6)

		if m.ReadOnly {
			opt[0] = "--bind-ro="
		} else {
			opt[0] = "--bind="
		}

		opt[1] = m.Source(absRoot)
		opt[2] = ":"
		opt[3] = filepath.Join(common.RelAppRootfsPath(appName), mntPath)
		opt[4] = ":"

		// If Recursive is not set, default to recursive.
		recursive := true
		if m.Volume.Recursive != nil {
			recursive = *m.Volume.Recursive
		}

		// rbind/norbind options exist since systemd-nspawn v226
		if recursive {
			opt[5] = "rbind"
		} else {
			opt[5] = "norbind"
		}
		args = append(args, strings.Join(opt, ""))
	}

	if !p.InsecureOptions.DisableCapabilities {
		capabilitiesStr, err := getAppCapabilities(app.Isolators)
		if err != nil {
			return nil, err
		}
		capList := strings.Join(capabilitiesStr, ",")
		args = append(args, "--capability="+capList)
	}

	return args, nil
}

// appToNspawnArgs transforms the given app manifest, with the given associated
// app name, into a subset of applicable systemd-nspawn argument
func (p *Pod) appToNspawnArgs(ra *schema.RuntimeApp) ([]string, error) {
	var args []string
	appName := ra.Name
	id := ra.Image.ID
	app := ra.App

	vols := make(map[types.ACName]types.Volume)

	// TODO(philips): this is implicitly creating a mapping from MountPoint
	// to volumes. This is a nice convenience for users but we will need to
	// introduce a --mount flag so they can control which mountPoint maps to
	// which volume.

	sharedVolPath := common.SharedVolumesPath(p.Root)
	if err := os.MkdirAll(sharedVolPath, sharedVolPerm); err != nil {
		return nil, fmt.Errorf("could not create shared volumes directory: %v", err)
	}
	if err := os.Chmod(sharedVolPath, sharedVolPerm); err != nil {
		return nil, fmt.Errorf("could not change permissions of %q: %v", sharedVolPath, err)
	}
	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
		if v.Kind == "empty" {
			if err := os.MkdirAll(filepath.Join(sharedVolPath, v.Name.String()), sharedVolPerm); err != nil {
				return nil, fmt.Errorf("could not create shared volume %q: %v", v.Name, err)
			}
		}
	}

	for _, mp := range app.MountPoints {
		key := mp.Name
		vol, ok := vols[key]
		if !ok {
			catCmd := fmt.Sprintf("sudo rkt image cat-manifest --pretty-print %v", id)
			volumeCmd := ""
			for _, mp := range app.MountPoints {
				volumeCmd += fmt.Sprintf("--volume %s,kind=host,source=/some/path ", mp.Name)
			}

			return nil, fmt.Errorf("no volume for mountpoint %q in app %q.\n"+
				"You can inspect the volumes with:\n\t%v\n"+
				"App %q requires the following volumes:\n\t%v",
				key, appName, catCmd, appName, volumeCmd)
		}
		opt := make([]string, 4)

		// If the readonly flag in the pod manifest is not nil,
		// then use it to override the readonly flag in the image manifest.
		readOnly := mp.ReadOnly
		if vol.ReadOnly != nil {
			readOnly = *vol.ReadOnly
		}

		if readOnly {
			opt[0] = "--bind-ro="
		} else {
			opt[0] = "--bind="
		}

		switch vol.Kind {
		case "host":
			opt[1] = vol.Source
		case "empty":
			absRoot, err := filepath.Abs(p.Root)
			if err != nil {
				return nil, fmt.Errorf("cannot get pod's root absolute path: %v\n", err)
			}
			opt[1] = filepath.Join(common.SharedVolumesPath(absRoot), vol.Name.String())
		default:
			return nil, fmt.Errorf(`invalid volume kind %q. Must be one of "host" or "empty".`, vol.Kind)
		}
		opt[2] = ":"
		opt[3] = filepath.Join(common.RelAppRootfsPath(appName), mp.Path)

		args = append(args, strings.Join(opt, ""))
	}

	for _, i := range app.Isolators {
		switch v := i.Value().(type) {
		case types.LinuxCapabilitiesSet:
			var caps []string
			// TODO: cleanup the API on LinuxCapabilitiesSet to give strings easily.
			for _, c := range v.Set() {
				caps = append(caps, string(c))
			}
			if i.Name == types.LinuxCapabilitiesRetainSetName {
				capList := strings.Join(caps, ",")
				args = append(args, "--capability="+capList)
			}
		}
	}

	return args, nil
}

// appToNspawnArgs transforms the given app manifest, with the given associated
// app name, into a subset of applicable systemd-nspawn argument
func appToNspawnArgs(p *stage1commontypes.Pod, ra *schema.RuntimeApp) ([]string, error) {
	var args []string
	appName := ra.Name
	app := ra.App

	sharedVolPath := common.SharedVolumesPath(p.Root)
	if err := os.MkdirAll(sharedVolPath, sharedVolPerm); err != nil {
		return nil, fmt.Errorf("could not create shared volumes directory: %v", err)
	}
	if err := os.Chmod(sharedVolPath, sharedVolPerm); err != nil {
		return nil, fmt.Errorf("could not change permissions of %q: %v", sharedVolPath, err)
	}

	vols := make(map[types.ACName]types.Volume)
	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
	}

	mounts := GenerateMounts(ra, vols)
	for _, m := range mounts {
		vol := vols[m.Volume]

		if vol.Kind == "empty" {
			p := filepath.Join(sharedVolPath, vol.Name.String())
			if err := os.MkdirAll(p, sharedVolPerm); err != nil {
				return nil, fmt.Errorf("could not create shared volume %q: %v", vol.Name, err)
			}
			if err := os.Chown(p, *vol.UID, *vol.GID); err != nil {
				return nil, fmt.Errorf("could not change owner of %q: %v", p, err)
			}
			mod, err := strconv.ParseUint(*vol.Mode, 8, 32)
			if err != nil {
				return nil, fmt.Errorf("invalid mode %q for volume %q: %v", *vol.Mode, vol.Name, err)
			}
			if err := os.Chmod(p, os.FileMode(mod)); err != nil {
				return nil, fmt.Errorf("could not change permissions of %q: %v", p, err)
			}
		}

		opt := make([]string, 4)

		if IsMountReadOnly(vol, app.MountPoints) {
			opt[0] = "--bind-ro="
		} else {
			opt[0] = "--bind="
		}

		switch vol.Kind {
		case "host":
			opt[1] = vol.Source
		case "empty":
			absRoot, err := filepath.Abs(p.Root)
			if err != nil {
				return nil, fmt.Errorf("cannot get pod's root absolute path: %v\n", err)
			}
			opt[1] = filepath.Join(common.SharedVolumesPath(absRoot), vol.Name.String())
		default:
			return nil, fmt.Errorf(`invalid volume kind %q. Must be one of "host" or "empty"`, vol.Kind)
		}
		opt[2] = ":"
		opt[3] = filepath.Join(common.RelAppRootfsPath(appName), m.Path)

		args = append(args, strings.Join(opt, ""))
	}

	for _, i := range app.Isolators {
		switch v := i.Value().(type) {
		case types.LinuxCapabilitiesSet:
			var caps []string
			// TODO: cleanup the API on LinuxCapabilitiesSet to give strings easily.
			for _, c := range v.Set() {
				caps = append(caps, string(c))
			}
			if i.Name == types.LinuxCapabilitiesRetainSetName {
				capList := strings.Join(caps, ",")
				args = append(args, "--capability="+capList)
			}
		}
	}

	return args, nil
}

// appToSystemd transforms the provided RuntimeApp+ImageManifest into systemd units
func appToSystemd(p *stage1commontypes.Pod, ra *schema.RuntimeApp, interactive bool, flavor string, privateUsers string) error {
	app := ra.App
	appName := ra.Name
	imgName := p.AppNameToImageName(appName)

	if len(app.Exec) == 0 {
		return fmt.Errorf(`image %q has an empty "exec" (try --exec=BINARY)`, imgName)
	}

	workDir := "/"
	if app.WorkingDirectory != "" {
		workDir = app.WorkingDirectory
	}

	env := app.Environment

	env.Set("AC_APP_NAME", appName.String())
	if p.MetadataServiceURL != "" {
		env.Set("AC_METADATA_URL", p.MetadataServiceURL)
	}

	if err := writeEnvFile(p, env, appName, privateUsers); err != nil {
		return errwrap.Wrap(errors.New("unable to write environment file"), err)
	}

	var _uid, gid int
	var err error

	uidRange := uid.NewBlankUidRange()
	if err := uidRange.Deserialize([]byte(privateUsers)); err != nil {
		return errwrap.Wrap(errors.New("unable to deserialize uid range"), err)
	}

	if strings.HasPrefix(app.User, "/") {
		var stat syscall.Stat_t
		if err = syscall.Lstat(filepath.Join(common.AppRootfsPath(p.Root, appName),
			app.User), &stat); err != nil {
			return errwrap.Wrap(fmt.Errorf("unable to get uid from file %q",
				app.User), err)
		}
		uidReal, _, err := uidRange.UnshiftRange(stat.Uid, 0)
		if err != nil {
			return errwrap.Wrap(errors.New("unable to determine real uid"), err)
		}
		_uid = int(uidReal)
	} else {
		_uid, err = strconv.Atoi(app.User)
		if err != nil {
			_uid, err = passwd.LookupUidFromFile(app.User,
				filepath.Join(common.AppRootfsPath(p.Root, appName), "etc/passwd"))
			if err != nil {
				return errwrap.Wrap(fmt.Errorf("cannot lookup user %q", app.User), err)
			}
		}
	}

	if strings.HasPrefix(app.Group, "/") {
		var stat syscall.Stat_t
		if err = syscall.Lstat(filepath.Join(common.AppRootfsPath(p.Root, appName),
			app.Group), &stat); err != nil {
			return errwrap.Wrap(fmt.Errorf("unable to get gid from file %q",
				app.Group), err)
		}
		_, gidReal, err := uidRange.UnshiftRange(0, stat.Gid)
		if err != nil {
			return errwrap.Wrap(errors.New("unable to determine real gid"), err)
		}
		gid = int(gidReal)
	} else {
		gid, err = strconv.Atoi(app.Group)
		if err != nil {
			gid, err = group.LookupGidFromFile(app.Group,
				filepath.Join(common.AppRootfsPath(p.Root, appName), "etc/group"))
			if err != nil {
				return errwrap.Wrap(fmt.Errorf("cannot lookup group %q", app.Group), err)
			}
		}
	}

	execWrap := []string{"/appexec", common.RelAppRootfsPath(appName), workDir, RelEnvFilePath(appName),
		strconv.Itoa(_uid), generateGidArg(gid, app.SupplementaryGIDs), "--"}
	execStart := quoteExec(append(execWrap, app.Exec...))
	opts := []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", fmt.Sprintf("Application=%v Image=%v", appName, imgName)),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "Wants", fmt.Sprintf("reaper-%s.service", appName)),
		unit.NewUnitOption("Service", "Restart", "no"),
		unit.NewUnitOption("Service", "ExecStart", execStart),
		unit.NewUnitOption("Service", "User", "0"),
		unit.NewUnitOption("Service", "Group", "0"),
	}

	if interactive {
		opts = append(opts, unit.NewUnitOption("Service", "StandardInput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "tty"))
	} else {
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "journal+console"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "journal+console"))
//.........这里部分代码省略.........

// appToNspawnArgs transforms the given app manifest, with the given associated
// app name, into a subset of applicable systemd-nspawn argument
func appToNspawnArgs(p *stage1commontypes.Pod, ra *schema.RuntimeApp) ([]string, error) {
	var args []string
	appName := ra.Name
	app := ra.App

	sharedVolPath := common.SharedVolumesPath(p.Root)
	if err := os.MkdirAll(sharedVolPath, SharedVolPerm); err != nil {
		return nil, errwrap.Wrap(errors.New("could not create shared volumes directory"), err)
	}
	if err := os.Chmod(sharedVolPath, SharedVolPerm); err != nil {
		return nil, errwrap.Wrap(fmt.Errorf("could not change permissions of %q", sharedVolPath), err)
	}

	vols := make(map[types.ACName]types.Volume)
	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
	}

	imageManifest := p.Images[appName.String()]
	mounts := GenerateMounts(ra, vols, imageManifest)
	for _, m := range mounts {
		vol := vols[m.Volume]

		shPath := filepath.Join(sharedVolPath, vol.Name.String())

		absRoot, err := filepath.Abs(p.Root) // Absolute path to the pod's rootfs.
		if err != nil {
			return nil, errwrap.Wrap(errors.New("could not get pod's root absolute path"), err)
		}

		appRootfs := common.AppRootfsPath(absRoot, appName)

		// TODO(yifan): This is a temporary fix for systemd-nspawn not handling symlink mounts well.
		// Could be removed when https://github.com/systemd/systemd/issues/2860 is resolved, and systemd
		// version is bumped.
		mntPath, err := EvaluateSymlinksInsideApp(appRootfs, m.Path)
		if err != nil {
			return nil, errwrap.Wrap(fmt.Errorf("could not evaluate path %v", m.Path), err)
		}
		mntAbsPath := filepath.Join(appRootfs, mntPath)

		if err := PrepareMountpoints(shPath, mntAbsPath, &vol, m.DockerImplicit); err != nil {
			return nil, err
		}

		opt := make([]string, 4)

		if IsMountReadOnly(vol, app.MountPoints) {
			opt[0] = "--bind-ro="
		} else {
			opt[0] = "--bind="
		}

		switch vol.Kind {
		case "host":
			opt[1] = vol.Source
		case "empty":
			opt[1] = filepath.Join(common.SharedVolumesPath(absRoot), vol.Name.String())
		default:
			return nil, fmt.Errorf(`invalid volume kind %q. Must be one of "host" or "empty"`, vol.Kind)
		}
		opt[2] = ":"
		opt[3] = filepath.Join(common.RelAppRootfsPath(appName), mntPath)
		args = append(args, strings.Join(opt, ""))
	}

	capabilitiesStr, err := getAppCapabilities(app.Isolators)
	if err != nil {
		return nil, err
	}
	capList := strings.Join(capabilitiesStr, ",")
	args = append(args, "--capability="+capList)

	return args, nil
}

// appToSystemd transforms the provided RuntimeApp+ImageManifest into systemd units
func appToSystemd(p *stage1commontypes.Pod, ra *schema.RuntimeApp, interactive bool, flavor string, privateUsers string) error {
	app := ra.App
	appName := ra.Name
	imgName := p.AppNameToImageName(appName)

	if len(app.Exec) == 0 {
		return fmt.Errorf(`image %q has an empty "exec" (try --exec=BINARY)`, imgName)
	}

	workDir := "/"
	if app.WorkingDirectory != "" {
		workDir = app.WorkingDirectory
	}

	env := app.Environment

	env.Set("AC_APP_NAME", appName.String())
	if p.MetadataServiceURL != "" {
		env.Set("AC_METADATA_URL", p.MetadataServiceURL)
	}

	envFilePath := EnvFilePath(p.Root, appName)

	uidRange := user.NewBlankUidRange()
	if err := uidRange.Deserialize([]byte(privateUsers)); err != nil {
		return err
	}

	if err := writeEnvFile(p, env, appName, uidRange, '\n', envFilePath); err != nil {
		return errwrap.Wrap(errors.New("unable to write environment file for systemd"), err)
	}

	u, g, err := parseUserGroup(p, ra, uidRange)
	if err != nil {
		return err
	}

	if err := generateSysusers(p, ra, u, g, uidRange); err != nil {
		return errwrap.Wrap(errors.New("unable to generate sysusers"), err)
	}

	binPath, err := findBinPath(p, appName, *app, workDir, app.Exec[0])
	if err != nil {
		return err
	}

	var supplementaryGroups []string
	for _, g := range app.SupplementaryGIDs {
		supplementaryGroups = append(supplementaryGroups, strconv.Itoa(g))
	}

	capabilitiesStr, err := getAppCapabilities(app.Isolators)
	if err != nil {
		return err
	}

	noNewPrivileges := getAppNoNewPrivileges(app.Isolators)

	execStart := append([]string{binPath}, app.Exec[1:]...)
	execStartString := quoteExec(execStart)
	opts := []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", fmt.Sprintf("Application=%v Image=%v", appName, imgName)),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "Wants", fmt.Sprintf("reaper-%s.service", appName)),
		unit.NewUnitOption("Service", "Restart", "no"),
		unit.NewUnitOption("Service", "ExecStart", execStartString),
		unit.NewUnitOption("Service", "RootDirectory", common.RelAppRootfsPath(appName)),
		// MountFlags=shared creates a new mount namespace and (as unintuitive
		// as it might seem) makes sure the mount is slave+shared.
		unit.NewUnitOption("Service", "MountFlags", "shared"),
		unit.NewUnitOption("Service", "WorkingDirectory", workDir),
		unit.NewUnitOption("Service", "EnvironmentFile", RelEnvFilePath(appName)),
		unit.NewUnitOption("Service", "User", strconv.Itoa(u)),
		unit.NewUnitOption("Service", "Group", strconv.Itoa(g)),
		unit.NewUnitOption("Service", "SupplementaryGroups", strings.Join(supplementaryGroups, " ")),
		unit.NewUnitOption("Service", "CapabilityBoundingSet", strings.Join(capabilitiesStr, " ")),
		unit.NewUnitOption("Service", "NoNewPrivileges", strconv.FormatBool(noNewPrivileges)),
		// This helps working around a race
		// (https://github.com/systemd/systemd/issues/2913) that causes the
		// systemd unit name not getting written to the journal if the unit is
		// short-lived and runs as non-root.
		unit.NewUnitOption("Service", "SyslogIdentifier", appName.String()),
	}

	// Restrict access to sensitive paths (eg. procfs)
	opts = protectSystemFiles(opts, appName)

	if ra.ReadOnlyRootFS {
		opts = append(opts, unit.NewUnitOption("Service", "ReadOnlyDirectories", common.RelAppRootfsPath(appName)))
	}

	// TODO(tmrts): Extract this logic into a utility function.
	vols := make(map[types.ACName]types.Volume)
	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
	}

	absRoot, err := filepath.Abs(p.Root) // Absolute path to the pod's rootfs.
	if err != nil {
//.........这里部分代码省略.........

func (uw *UnitWriter) AppUnit(
	ra *schema.RuntimeApp, binPath, privateUsers string, insecureOptions Stage1InsecureOptions,
	opts ...*unit.UnitOption,
) {
	if uw.err != nil {
		return
	}

	flavor, systemdVersion, err := GetFlavor(uw.p)
	if err != nil {
		uw.err = errwrap.Wrap(errors.New("unable to determine stage1 flavor"), err)
		return
	}

	app := ra.App
	appName := ra.Name
	imgName := uw.p.AppNameToImageName(appName)

	if len(app.Exec) == 0 {
		uw.err = fmt.Errorf(`image %q has an empty "exec" (try --exec=BINARY)`, imgName)
		return
	}

	env := app.Environment

	env.Set("AC_APP_NAME", appName.String())
	if uw.p.MetadataServiceURL != "" {
		env.Set("AC_METADATA_URL", uw.p.MetadataServiceURL)
	}

	envFilePath := EnvFilePath(uw.p.Root, appName)

	uidRange := user.NewBlankUidRange()
	if err := uidRange.Deserialize([]byte(privateUsers)); err != nil {
		uw.err = err
		return
	}

	if err := common.WriteEnvFile(env, uidRange, envFilePath); err != nil {
		uw.err = errwrap.Wrap(errors.New("unable to write environment file for systemd"), err)
		return
	}

	u, g, err := parseUserGroup(uw.p, ra, uidRange)
	if err != nil {
		uw.err = err
		return
	}

	if err := generateSysusers(uw.p, ra, u, g, uidRange); err != nil {
		uw.err = errwrap.Wrap(errors.New("unable to generate sysusers"), err)
		return
	}

	var supplementaryGroups []string
	for _, g := range app.SupplementaryGIDs {
		supplementaryGroups = append(supplementaryGroups, strconv.Itoa(g))
	}

	capabilitiesStr, err := getAppCapabilities(app.Isolators)
	if err != nil {
		uw.err = err
		return
	}

	execStart := append([]string{binPath}, app.Exec[1:]...)
	execStartString := quoteExec(execStart)
	opts = append(opts, []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", fmt.Sprintf("Application=%v Image=%v", appName, imgName)),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "Wants", fmt.Sprintf("reaper-%s.service", appName)),
		unit.NewUnitOption("Service", "Restart", "no"),
		unit.NewUnitOption("Service", "ExecStart", execStartString),
		unit.NewUnitOption("Service", "RootDirectory", common.RelAppRootfsPath(appName)),
		// MountFlags=shared creates a new mount namespace and (as unintuitive
		// as it might seem) makes sure the mount is slave+shared.
		unit.NewUnitOption("Service", "MountFlags", "shared"),
		unit.NewUnitOption("Service", "WorkingDirectory", app.WorkingDirectory),
		unit.NewUnitOption("Service", "EnvironmentFile", RelEnvFilePath(appName)),
		unit.NewUnitOption("Service", "User", strconv.Itoa(u)),
		unit.NewUnitOption("Service", "Group", strconv.Itoa(g)),

		// This helps working around a race
		// (https://github.com/systemd/systemd/issues/2913) that causes the
		// systemd unit name not getting written to the journal if the unit is
		// short-lived and runs as non-root.
		unit.NewUnitOption("Service", "SyslogIdentifier", appName.String()),
	}...)

	if len(supplementaryGroups) > 0 {
		opts = appendOptionsList(opts, "Service", "SupplementaryGroups", "", supplementaryGroups)
	}

	if supportsNotify(uw.p, appName.String()) {
		opts = append(opts, unit.NewUnitOption("Service", "Type", "notify"))
	}

	if !insecureOptions.DisableCapabilities {
		opts = append(opts, unit.NewUnitOption("Service", "CapabilityBoundingSet", strings.Join(capabilitiesStr, " ")))
	}
//.........这里部分代码省略.........

// appToNspawnArgs transforms the given app manifest, with the given associated
// app image id, into a subset of applicable systemd-nspawn argument
func (p *Pod) appToNspawnArgs(ra *schema.RuntimeApp) ([]string, error) {
	args := []string{}
	name := ra.Name.String()
	id := ra.Image.ID
	app := ra.App

	vols := make(map[types.ACName]types.Volume)

	// TODO(philips): this is implicitly creating a mapping from MountPoint
	// to volumes. This is a nice convenience for users but we will need to
	// introduce a --mount flag so they can control which mountPoint maps to
	// which volume.

	for _, v := range p.Manifest.Volumes {
		vols[v.Name] = v
	}

	for _, mp := range app.MountPoints {
		key := mp.Name
		vol, ok := vols[key]
		if !ok {
			catCmd := fmt.Sprintf("sudo rkt image cat-manifest --pretty-print %v", id)
			volumeCmd := ""
			for _, mp := range app.MountPoints {
				volumeCmd += fmt.Sprintf("--volume %s,kind=host,source=/some/path ", mp.Name)
			}

			return nil, fmt.Errorf("no volume for mountpoint %q in app %q.\n"+
				"You can inspect the volumes with:\n\t%v\n"+
				"App %q requires the following volumes:\n\t%v",
				key, name, catCmd, name, volumeCmd)
		}
		opt := make([]string, 4)

		// If the readonly flag in the pod manifest is not nil,
		// then use it to override the readonly flag in the image manifest.
		readOnly := mp.ReadOnly
		if vol.ReadOnly != nil {
			readOnly = *vol.ReadOnly
		}

		if readOnly {
			opt[0] = "--bind-ro="
		} else {
			opt[0] = "--bind="
		}

		opt[1] = vol.Source
		opt[2] = ":"
		opt[3] = filepath.Join(common.RelAppRootfsPath(id), mp.Path)

		args = append(args, strings.Join(opt, ""))
	}

	for _, i := range app.Isolators {
		switch v := i.Value().(type) {
		case types.LinuxCapabilitiesSet:
			var caps []string
			// TODO: cleanup the API on LinuxCapabilitiesSet to give strings easily.
			for _, c := range v.Set() {
				caps = append(caps, string(c))
			}
			if i.Name == types.LinuxCapabilitiesRetainSetName {
				capList := strings.Join(caps, ",")
				args = append(args, "--capability="+capList)
			}
		}
	}

	return args, nil
}

// InstantiatedPrepareAppUnitName returns the systemd service unit name for prepare-app
// instantiated for the given root.
func InstantiatedPrepareAppUnitName(appName types.ACName) string {
	// Naming respecting escaping rules, see systemd.unit(5) and systemd-escape(1)
	escapedRoot := unit.UnitNamePathEscape(common.RelAppRootfsPath(appName))
	return "[email protected]" + escapedRoot + ".service"
}

// appToSystemd transforms the provided RuntimeApp+ImageManifest into systemd units
func appToSystemd(p *stage1commontypes.Pod, ra *schema.RuntimeApp, interactive bool, flavor string, privateUsers string) error {
	app := ra.App
	appName := ra.Name
	image, ok := p.Images[appName.String()]
	if !ok {
		// This is impossible as we have updated the map in LoadPod().
		panic(fmt.Sprintf("No images for app %q", ra.Name.String()))
	}
	imgName := image.Name

	if len(app.Exec) == 0 {
		return fmt.Errorf(`image %q has an empty "exec" (try --exec=BINARY)`, imgName)
	}

	workDir := "/"
	if app.WorkingDirectory != "" {
		workDir = app.WorkingDirectory
	}

	env := app.Environment

	env.Set("AC_APP_NAME", appName.String())
	if p.MetadataServiceURL != "" {
		env.Set("AC_METADATA_URL", p.MetadataServiceURL)
	}

	if err := writeEnvFile(p, env, appName, privateUsers); err != nil {
		return fmt.Errorf("unable to write environment file: %v", err)
	}

	// This is a partial implementation for app.User and app.Group:
	// For now, only numeric ids (and the string "root") are supported.
	var uid, gid int
	var err error
	if app.User == "root" {
		uid = 0
	} else {
		uid, err = strconv.Atoi(app.User)
		if err != nil {
			return fmt.Errorf("non-numerical user id not supported yet")
		}
	}
	if app.Group == "root" {
		gid = 0
	} else {
		gid, err = strconv.Atoi(app.Group)
		if err != nil {
			return fmt.Errorf("non-numerical group id not supported yet")
		}
	}

	execWrap := []string{"/appexec", common.RelAppRootfsPath(appName), workDir, RelEnvFilePath(appName), strconv.Itoa(uid), generateGidArg(gid, app.SupplementaryGIDs)}
	execStart := quoteExec(append(execWrap, app.Exec...))
	opts := []*unit.UnitOption{
		unit.NewUnitOption("Unit", "Description", fmt.Sprintf("Application=%v Image=%v", appName, imgName)),
		unit.NewUnitOption("Unit", "DefaultDependencies", "false"),
		unit.NewUnitOption("Unit", "Wants", fmt.Sprintf("reaper-%s.service", appName)),
		unit.NewUnitOption("Service", "Restart", "no"),
		unit.NewUnitOption("Service", "ExecStart", execStart),
		unit.NewUnitOption("Service", "User", "0"),
		unit.NewUnitOption("Service", "Group", "0"),
	}

	if interactive {
		opts = append(opts, unit.NewUnitOption("Service", "StandardInput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "tty"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "tty"))
	} else {
		opts = append(opts, unit.NewUnitOption("Service", "StandardOutput", "journal+console"))
		opts = append(opts, unit.NewUnitOption("Service", "StandardError", "journal+console"))
		opts = append(opts, unit.NewUnitOption("Service", "SyslogIdentifier", filepath.Base(app.Exec[0])))
	}

	// When an app fails, we shut down the pod
	opts = append(opts, unit.NewUnitOption("Unit", "OnFailure", "halt.target"))

	for _, eh := range app.EventHandlers {
		var typ string
		switch eh.Name {
		case "pre-start":
			typ = "ExecStartPre"
		case "post-stop":
			typ = "ExecStopPost"
		default:
			return fmt.Errorf("unrecognized eventHandler: %v", eh.Name)
		}
		exec := quoteExec(append(execWrap, eh.Exec...))
		opts = append(opts, unit.NewUnitOption("Service", typ, exec))
	}

	// Some pre-start jobs take a long time, set the timeout to 0
	opts = append(opts, unit.NewUnitOption("Service", "TimeoutStartSec", "0"))

	var saPorts []types.Port
	for _, p := range app.Ports {
		if p.SocketActivated {
			saPorts = append(saPorts, p)
		}
	}
//.........这里部分代码省略.........