2 files changed, 50 insertions, 3 deletions
diff --git a/utils/utils.go b/utils/utils.go
index 2e415130e..b08630d2f 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -4,12 +4,15 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"os/exec"
 	"strconv"
 	"strings"
+	"sync"
 
 	"github.com/containers/podman/v3/libpod/define"
+	"github.com/containers/podman/v3/pkg/cgroups"
 	"github.com/containers/storage/pkg/archive"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -155,3 +158,47 @@ func RemoveScientificNotationFromFloat(x float64) (float64, error) {
 	}
 	return result, nil
 }
+
+var (
+	runsOnSystemdOnce sync.Once
+	runsOnSystemd     bool
+)
+
+// RunsOnSystemd returns whether the system is using systemd
+func RunsOnSystemd() bool {
+	runsOnSystemdOnce.Do(func() {
+		initCommand, err := ioutil.ReadFile("/proc/1/comm")
+		// On errors, default to systemd
+		runsOnSystemd = err != nil || strings.TrimRight(string(initCommand), "\n") == "systemd"
+	})
+	return runsOnSystemd
+}
+
+func moveProcessToScope(pidPath, slice, scope string) error {
+	data, err := ioutil.ReadFile(pidPath)
+	if err != nil {
+		return errors.Wrapf(err, "cannot read pid file %s", pidPath)
+	}
+	pid, err := strconv.ParseUint(string(data), 10, 0)
+	if err != nil {
+		return errors.Wrapf(err, "cannot parse pid file %s", pidPath)
+	}
+	return RunUnderSystemdScope(int(pid), slice, scope)
+}
+
+// MovePauseProcessToScope moves the pause process used for rootless mode to keep the namespaces alive to
+// a separate scope.
+func MovePauseProcessToScope(pausePidPath string) {
+	err := moveProcessToScope(pausePidPath, "user.slice", "podman-pause.scope")
+	if err != nil {
+		unified, err := cgroups.IsCgroup2UnifiedMode()
+		if err != nil {
+			logrus.Warnf("Failed to detect if running with cgroup unified: %v", err)
+		}
+		if RunsOnSystemd() && unified {
+			logrus.Warnf("Failed to add pause process to systemd sandbox cgroup: %v", err)
+		} else {
+			logrus.Debugf("Failed to add pause process to systemd sandbox cgroup: %v", err)
+		}
+	}
+}
diff --git a/utils/utils_supported.go b/utils/utils_supported.go
index ebc870d26..1404e3194 100644
--- a/utils/utils_supported.go
+++ b/utils/utils_supported.go
@@ -47,10 +47,10 @@ func RunUnderSystemdScope(pid int, slice string, unitName string) error {
 		// On errors check if the cgroup already exists, if it does move the process there
 		if props, err := conn.GetUnitTypeProperties(unitName, "Scope"); err == nil {
 			if cgroup, ok := props["ControlGroup"].(string); ok && cgroup != "" {
-				if err := moveUnderCgroup(cgroup, "", []uint32{uint32(pid)}); err != nil {
-					return err
+				if err := moveUnderCgroup(cgroup, "", []uint32{uint32(pid)}); err == nil {
+					return nil
 				}
-				return nil
+				// On errors return the original error message we got from StartTransientUnit.
 			}
 		}
 		return err