system: add new subcommand "migrate"

it is useful to migrate existing containers to a new version of
podman.  Currently, it is needed to migrate rootless containers that
were created with podman <= 1.2 to a newer version which requires all
containers to be running in the same user namespace.

Closes: https://github.com/containers/libpod/issues/2935

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/libpod/runtime_migrate.go b/libpod/runtime_migrate.go
new file mode 100644
index 000000000..7d7fa108d
--- /dev/null
+++ b/libpod/runtime_migrate.go
@@ -0,0 +1,48 @@
+package libpod
+
+import (
+	"context"
+	"path/filepath"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+func (r *Runtime) migrate() error {
+	runningContainers, err := r.GetRunningContainers()
+	if err != nil {
+		return err
+	}
+
+	allCtrs, err := r.state.AllContainers()
+	if err != nil {
+		return err
+	}
+
+	logrus.Infof("stopping all containers")
+	for _, ctr := range runningContainers {
+		logrus.Infof("stopping %s", ctr.ID())
+		if err := ctr.Stop(); err != nil {
+			return errors.Wrapf(err, "cannot stop container %s", ctr.ID())
+		}
+	}
+
+	for _, ctr := range allCtrs {
+		oldLocation := filepath.Join(ctr.state.RunDir, "conmon.pid")
+		if ctr.config.ConmonPidFile == oldLocation {
+			logrus.Infof("changing conmon PID file for %s", ctr.ID())
+			ctr.config.ConmonPidFile = filepath.Join(ctr.config.StaticDir, "conmon.pid")
+			if err := r.state.RewriteContainerConfig(ctr, ctr.config); err != nil {
+				return errors.Wrapf(err, "error rewriting config for container %s", ctr.ID())
+			}
+		}
+	}
+
+	for _, ctr := range runningContainers {
+		if err := ctr.Start(context.Background(), true); err != nil {
+			logrus.Errorf("error restarting container %s", ctr.ID())
+		}
+	}
+
+	return nil
+}