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, 50 insertions, 0 deletions

diff --git a/cmd/podman/system_migrate.go b/cmd/podman/system_migrate.go
new file mode 100644
index 000000000..b08eedcde
--- /dev/null
+++ b/cmd/podman/system_migrate.go
@@ -0,0 +1,50 @@
+package main
+
+import (
+	"github.com/containers/libpod/cmd/podman/cliconfig"
+	"github.com/containers/libpod/cmd/podman/libpodruntime"
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+var (
+	migrateCommand     cliconfig.SystemMigrateValues
+	migrateDescription = `
+        podman system migrate
+
+        Migrate existing containers to a new version of Podman.
+`
+
+	_migrateCommand = &cobra.Command{
+		Use:   "migrate",
+		Args:  noSubArgs,
+		Short: "Migrate containers",
+		Long:  migrateDescription,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			migrateCommand.InputArgs = args
+			migrateCommand.GlobalFlags = MainGlobalOpts
+			return migrateCmd(&migrateCommand)
+		},
+	}
+)
+
+func init() {
+	migrateCommand.Command = _migrateCommand
+	migrateCommand.SetHelpTemplate(HelpTemplate())
+	migrateCommand.SetUsageTemplate(UsageTemplate())
+}
+
+func migrateCmd(c *cliconfig.SystemMigrateValues) error {
+	// We need to pass one extra option to NewRuntime.
+	// This will inform the OCI runtime to start a migrate.
+	// That's controlled by the last argument to GetRuntime.
+	r, err := libpodruntime.GetRuntimeMigrate(&c.PodmanCommand)
+	if err != nil {
+		return errors.Wrapf(err, "error migrating containers")
+	}
+	if err := r.Shutdown(false); err != nil {
+		return err
+	}
+
+	return nil
+}