Merge pull request #3397 from giuseppe/fix-reboot

rootless: enable linger if /run/user/UID not exists

cmd/podman/main.go

@@ -100,7 +100,7 @@ func initConfig() {
 }
 
 func before(cmd *cobra.Command, args []string) error {
-	if err := libpod.SetXdgRuntimeDir(""); err != nil {
+	if err := libpod.SetXdgRuntimeDir(); err != nil {
 		logrus.Errorf(err.Error())
 		os.Exit(1)
 	}

libpod/runtime.go

@@ -10,6 +10,7 @@ import (
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	"github.com/BurntSushi/toml"
 	is "github.com/containers/image/storage"
@@ -312,18 +313,39 @@ func defaultRuntimeConfig() (RuntimeConfig, error) {
 
 // SetXdgRuntimeDir ensures the XDG_RUNTIME_DIR env variable is set
 // containers/image uses XDG_RUNTIME_DIR to locate the auth file.
-func SetXdgRuntimeDir(val string) error {
+// It internally calls EnableLinger() so that the user's processes are not
+// killed once the session is terminated.  EnableLinger() also attempts to
+// get the runtime directory when XDG_RUNTIME_DIR is not specified.
+func SetXdgRuntimeDir() error {
 	if !rootless.IsRootless() {
 		return nil
 	}
-	if val == "" {
+
+	runtimeDir := os.Getenv("XDG_RUNTIME_DIR")
+
+	runtimeDirLinger, err := rootless.EnableLinger()
+	if err != nil {
+		return errors.Wrapf(err, "error enabling user session")
+	}
+	if runtimeDir == "" && runtimeDirLinger != "" {
+		if _, err := os.Stat(runtimeDirLinger); err != nil && os.IsNotExist(err) {
+			chWait := make(chan error)
+			defer close(chWait)
+			if _, err := WaitForFile(runtimeDirLinger, chWait, time.Second*10); err != nil {
+				return errors.Wrapf(err, "waiting for directory '%s'", runtimeDirLinger)
+			}
+		}
+		runtimeDir = runtimeDirLinger
+	}
+
+	if runtimeDir == "" {
 		var err error
-		val, err = util.GetRootlessRuntimeDir()
+		runtimeDir, err = util.GetRootlessRuntimeDir()
 		if err != nil {
 			return err
 		}
 	}
-	if err := os.Setenv("XDG_RUNTIME_DIR", val); err != nil {
+	if err := os.Setenv("XDG_RUNTIME_DIR", runtimeDir); err != nil {
 		return errors.Wrapf(err, "cannot set XDG_RUNTIME_DIR")
 	}
 	return nil
@@ -479,18 +501,6 @@ func newRuntimeFromConfig(ctx context.Context, userConfigPath string, options ..
 				runtime.config.SignaturePolicyPath = newPath
 			}
 		}
-
-		runtimeDir, err := util.GetRootlessRuntimeDir()
-		if err != nil {
-			return nil, err
-		}
-
-		// containers/image uses XDG_RUNTIME_DIR to locate the auth file.
-		// So make sure the env variable is set.
-		if err := SetXdgRuntimeDir(runtimeDir); err != nil {
-			return nil, errors.Wrapf(err, "cannot set XDG_RUNTIME_DIR")
-		}
-
 	}
 
 	if userConfigPath != "" {

pkg/rootless/rootless_linux.go

@@ -9,14 +9,17 @@ import (
 	"os/exec"
 	gosignal "os/signal"
 	"os/user"
+	"path/filepath"
 	"runtime"
 	"strconv"
+	"strings"
 	"sync"
 	"syscall"
 	"unsafe"
 
 	"github.com/containers/storage/pkg/idtools"
 	"github.com/docker/docker/pkg/signal"
+	"github.com/godbus/dbus"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
 )
@@ -198,24 +201,90 @@ func getUserNSFirstChild(fd uintptr) (*os.File, error) {
 	}
 }
 
-func enableLinger(pausePid string) {
-	if pausePid == "" {
-		return
+// EnableLinger configures the system to not kill the user processes once the session
+// terminates
+func EnableLinger() (string, error) {
+	uid := fmt.Sprintf("%d", GetRootlessUID())
+
+	conn, err := dbus.SystemBus()
+	if err == nil {
+		defer conn.Close()
 	}
-	// If we are trying to write a pause pid file, make sure we can leave processes
-	// running longer than the user session.
-	err := exec.Command("loginctl", "enable-linger", fmt.Sprintf("%d", GetRootlessUID())).Run()
+
+	lingerEnabled := false
+
+	// If we have a D-BUS connection, attempt to read the LINGER property from it.
+	if conn != nil {
+		path := dbus.ObjectPath((fmt.Sprintf("/org/freedesktop/login1/user/_%s", uid)))
+		ret, err := conn.Object("org.freedesktop.login1", path).GetProperty("org.freedesktop.login1.User.Linger")
+		if err == nil && ret.Value().(bool) {
+			lingerEnabled = true
+		}
+	}
+
+	xdgRuntimeDir := os.Getenv("XDG_RUNTIME_DIR")
+	lingerFile := ""
+	if xdgRuntimeDir != "" && !lingerEnabled {
+		lingerFile = filepath.Join(xdgRuntimeDir, "libpod/linger")
+		_, err := os.Stat(lingerFile)
+		if err == nil {
+			lingerEnabled = true
+		}
+	}
+
+	if !lingerEnabled {
+		// First attempt with D-BUS, if it fails, then attempt with "loginctl enable-linger"
+		if conn != nil {
+			o := conn.Object("org.freedesktop.login1", "/org/freedesktop/login1")
+			ret := o.Call("org.freedesktop.login1.Manager.SetUserLinger", 0, uint32(GetRootlessUID()), true, true)
+			if ret.Err == nil {
+				lingerEnabled = true
+			}
+		}
+		if !lingerEnabled {
+			err := exec.Command("loginctl", "enable-linger", uid).Run()
+			if err == nil {
+				lingerEnabled = true
+			} else {
+				logrus.Debugf("cannot run `loginctl enable-linger` for the current user: %v", err)
+			}
+		}
+		if lingerEnabled && lingerFile != "" {
+			f, err := os.Create(lingerFile)
+			if err == nil {
+				f.Close()
+			} else {
+				logrus.Debugf("could not create linger file: %v", err)
+			}
+		}
+	}
+
+	if !lingerEnabled {
+		return "", nil
+	}
+
+	// If we have a D-BUS connection, attempt to read the RUNTIME PATH from it.
+	if conn != nil {
+		path := dbus.ObjectPath((fmt.Sprintf("/org/freedesktop/login1/user/_%s", uid)))
+		ret, err := conn.Object("org.freedesktop.login1", path).GetProperty("org.freedesktop.login1.User.RuntimePath")
+		if err == nil {
+			return strings.Trim(ret.String(), "\"\n"), nil
+		}
+	}
+
+	// If XDG_RUNTIME_DIR is not set and the D-BUS call didn't work, try to get the runtime path with "loginctl"
+	output, err := exec.Command("loginctl", "-pRuntimePath", "show-user", uid).Output()
 	if err != nil {
-		logrus.Warnf("cannot run `loginctl enable-linger` for the current user: %v", err)
+		logrus.Debugf("could not get RuntimePath using loginctl: %v", err)
+		return "", nil
 	}
+	return strings.Trim(strings.Replace(string(output), "RuntimePath=", "", -1), "\"\n"), nil
 }
 
 // joinUserAndMountNS re-exec podman in a new userNS and join the user and mount
 // namespace of the specified PID without looking up its parent.  Useful to join directly
 // the conmon process.
 func joinUserAndMountNS(pid uint, pausePid string) (bool, int, error) {
-	enableLinger(pausePid)
-
 	if os.Geteuid() == 0 || os.Getenv("_CONTAINERS_USERNS_CONFIGURED") != "" {
 		return false, -1, nil
 	}
@@ -406,7 +475,6 @@ func becomeRootInUserNS(pausePid, fileToRead string, fileOutput *os.File) (bool,
 // If podman was re-executed the caller needs to propagate the error code returned by the child
 // process.
 func BecomeRootInUserNS(pausePid string) (bool, int, error) {
-	enableLinger(pausePid)
 	return becomeRootInUserNS(pausePid, "", nil)
 }
 

pkg/rootless/rootless_unsupported.go

@@ -29,6 +29,12 @@ func GetRootlessGID() int {
 	return -1
 }
 
+// EnableLinger configures the system to not kill the user processes once the session
+// terminates
+func EnableLinger() (string, error) {
+	return "", nil
+}
+
 // TryJoinFromFilePaths attempts to join the namespaces of the pid files in paths.
 // This is useful when there are already running containers and we
 // don't have a pause process yet.  We can use the paths to the conmon