Migrate can move containers to a new runtime

This is a horrible hack to work around issues with Fedora 31, but
other distros might need it to, so we'll move it upstream.

I do not recommend this functionality for general use, and the
manpages and other documentation will reflect this. But for some
upgrade cases, it will be the only thing that allows for a
working system.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

3 files changed, 14 insertions, 8 deletions

diff --git a/cmd/podman/cliconfig/config.go b/cmd/podman/cliconfig/config.go
index 5b5225f02..4831b7971 100644
--- a/cmd/podman/cliconfig/config.go
+++ b/cmd/podman/cliconfig/config.go
@@ -651,6 +651,7 @@ type SystemRenumberValues struct {
 
 type SystemMigrateValues struct {
 	PodmanCommand
+	NewRuntime string
 }
 
 type SystemDfValues struct {
diff --git a/cmd/podman/libpodruntime/runtime.go b/cmd/podman/libpodruntime/runtime.go
index 6dafeb0b0..dd8c3f173 100644
--- a/cmd/podman/libpodruntime/runtime.go
+++ b/cmd/podman/libpodruntime/runtime.go
@@ -14,31 +14,31 @@ import (
 )
 
 // GetRuntimeMigrate gets a libpod runtime that will perform a migration of existing containers
-func GetRuntimeMigrate(ctx context.Context, c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(ctx, c, false, true, false, true)
+func GetRuntimeMigrate(ctx context.Context, c *cliconfig.PodmanCommand, newRuntime string) (*libpod.Runtime, error) {
+	return getRuntime(ctx, c, false, true, false, true, newRuntime)
 }
 
 // GetRuntimeDisableFDs gets a libpod runtime that will disable sd notify
 func GetRuntimeDisableFDs(ctx context.Context, c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(ctx, c, false, false, false, false)
+	return getRuntime(ctx, c, false, false, false, false, "")
 }
 
 // GetRuntimeRenumber gets a libpod runtime that will perform a lock renumber
 func GetRuntimeRenumber(ctx context.Context, c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(ctx, c, true, false, false, true)
+	return getRuntime(ctx, c, true, false, false, true, "")
 }
 
 // GetRuntime generates a new libpod runtime configured by command line options
 func GetRuntime(ctx context.Context, c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(ctx, c, false, false, false, true)
+	return getRuntime(ctx, c, false, false, false, true, "")
 }
 
 // GetRuntimeNoStore generates a new libpod runtime configured by command line options
 func GetRuntimeNoStore(ctx context.Context, c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(ctx, c, false, false, true, true)
+	return getRuntime(ctx, c, false, false, true, true, "")
 }
 
-func getRuntime(ctx context.Context, c *cliconfig.PodmanCommand, renumber, migrate, noStore, withFDS bool) (*libpod.Runtime, error) {
+func getRuntime(ctx context.Context, c *cliconfig.PodmanCommand, renumber, migrate, noStore, withFDS bool, newRuntime string) (*libpod.Runtime, error) {
 	options := []libpod.RuntimeOption{}
 	storageOpts := storage.StoreOptions{}
 	storageSet := false
@@ -88,6 +88,9 @@ func getRuntime(ctx context.Context, c *cliconfig.PodmanCommand, renumber, migra
 	}
 	if migrate {
 		options = append(options, libpod.WithMigrate())
+		if newRuntime != "" {
+			options = append(options, libpod.WithMigrateRuntime(newRuntime))
+		}
 	}
 
 	if renumber {
diff --git a/cmd/podman/system_migrate.go b/cmd/podman/system_migrate.go
index 4a0afcfad..9c90aeb52 100644
--- a/cmd/podman/system_migrate.go
+++ b/cmd/podman/system_migrate.go
@@ -32,13 +32,15 @@ func init() {
 	migrateCommand.Command = _migrateCommand
 	migrateCommand.SetHelpTemplate(HelpTemplate())
 	migrateCommand.SetUsageTemplate(UsageTemplate())
+	flags := migrateCommand.Flags()
+	flags.StringVar(&migrateCommand.NewRuntime, "new-runtime", "", "Specify a new runtime for all containers")
 }
 
 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(getContext(), &c.PodmanCommand)
+	r, err := libpodruntime.GetRuntimeMigrate(getContext(), &c.PodmanCommand, c.NewRuntime)
 	if err != nil {
 		return errors.Wrapf(err, "error migrating containers")
 	}