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>

5 files changed, 67 insertions, 4 deletions

diff --git a/cmd/podman/cliconfig/config.go b/cmd/podman/cliconfig/config.go
index 640a4bff4..77156f47a 100644
--- a/cmd/podman/cliconfig/config.go
+++ b/cmd/podman/cliconfig/config.go
@@ -581,6 +581,10 @@ type SystemRenumberValues struct {
 	PodmanCommand
 }
 
+type SystemMigrateValues struct {
+	PodmanCommand
+}
+
 type SystemDfValues struct {
 	PodmanCommand
 	Verbose bool
diff --git a/cmd/podman/commands.go b/cmd/podman/commands.go
index c43ecec5c..36c28696f 100644
--- a/cmd/podman/commands.go
+++ b/cmd/podman/commands.go
@@ -77,6 +77,7 @@ func getSystemSubCommands() []*cobra.Command {
 		_pruneSystemCommand,
 		_renumberCommand,
 		_dfSystemCommand,
+		_migrateCommand,
 	}
 }
 
diff --git a/cmd/podman/libpodruntime/runtime.go b/cmd/podman/libpodruntime/runtime.go
index 78adf1252..595f8267f 100644
--- a/cmd/podman/libpodruntime/runtime.go
+++ b/cmd/podman/libpodruntime/runtime.go
@@ -9,17 +9,22 @@ import (
 	"github.com/pkg/errors"
 )
 
+// GetRuntimeMigrate gets a libpod runtime that will perform a migration of existing containers
+func GetRuntimeMigrate(c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
+	return getRuntime(c, false, true)
+}
+
 // GetRuntimeRenumber gets a libpod runtime that will perform a lock renumber
 func GetRuntimeRenumber(c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(c, true)
+	return getRuntime(c, true, false)
 }
 
 // GetRuntime generates a new libpod runtime configured by command line options
 func GetRuntime(c *cliconfig.PodmanCommand) (*libpod.Runtime, error) {
-	return getRuntime(c, false)
+	return getRuntime(c, false, false)
 }
 
-func getRuntime(c *cliconfig.PodmanCommand, renumber bool) (*libpod.Runtime, error) {
+func getRuntime(c *cliconfig.PodmanCommand, renumber bool, migrate bool) (*libpod.Runtime, error) {
 	options := []libpod.RuntimeOption{}
 	storageOpts := storage.StoreOptions{}
 	storageSet := false
@@ -63,6 +68,9 @@ func getRuntime(c *cliconfig.PodmanCommand, renumber bool) (*libpod.Runtime, err
 		storageSet = true
 		storageOpts.GraphDriverOptions = c.GlobalFlags.StorageOpts
 	}
+	if migrate {
+		options = append(options, libpod.WithMigrate())
+	}
 
 	if renumber {
 		options = append(options, libpod.WithRenumber())
diff --git a/cmd/podman/main_local.go b/cmd/podman/main_local.go
index 91ad42630..42a8e434e 100644
--- a/cmd/podman/main_local.go
+++ b/cmd/podman/main_local.go
@@ -103,7 +103,7 @@ func profileOff(cmd *cobra.Command) error {
 }
 
 func setupRootless(cmd *cobra.Command, args []string) error {
-	if os.Geteuid() == 0 || cmd == _searchCommand || cmd == _versionCommand || cmd == _mountCommand || strings.HasPrefix(cmd.Use, "help") {
+	if os.Geteuid() == 0 || cmd == _searchCommand || cmd == _versionCommand || cmd == _mountCommand || cmd == _migrateCommand || strings.HasPrefix(cmd.Use, "help") {
 		return nil
 	}
 	podmanCmd := cliconfig.PodmanCommand{
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
+}