Merge pull request #16888 from Luap99/export-fd

export: use io.Writer instead of file

cmd/podman/containers/export.go

@@ -43,13 +43,14 @@ var (
 
 var (
 	exportOpts entities.ContainerExportOptions
+	outputFile string
 )
 
 func exportFlags(cmd *cobra.Command) {
 	flags := cmd.Flags()
 
 	outputFlagName := "output"
-	flags.StringVarP(&exportOpts.Output, outputFlagName, "o", "", "Write to a specified file (default: stdout, which must be redirected)")
+	flags.StringVarP(&outputFile, outputFlagName, "o", "", "Write to a specified file (default: stdout, which must be redirected)")
 	_ = cmd.RegisterFlagCompletionFunc(outputFlagName, completion.AutocompleteDefault)
 }
 
@@ -67,14 +68,24 @@ func init() {
 }
 
 func export(cmd *cobra.Command, args []string) error {
-	if len(exportOpts.Output) == 0 {
+	if len(outputFile) == 0 {
 		file := os.Stdout
 		if term.IsTerminal(int(file.Fd())) {
 			return errors.New("refusing to export to terminal. Use -o flag or redirect")
 		}
-		exportOpts.Output = "/dev/stdout"
-	} else if err := parse.ValidateFileName(exportOpts.Output); err != nil {
-		return err
+		exportOpts.Output = file
+	} else {
+		if err := parse.ValidateFileName(outputFile); err != nil {
+			return err
+		}
+		// open file here with WRONLY since on MacOS it can fail to open /dev/stderr in read mode for example
+		// https://github.com/containers/podman/issues/16870
+		file, err := os.OpenFile(outputFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+		if err != nil {
+			return err
+		}
+		defer file.Close()
+		exportOpts.Output = file
 	}
 	return registry.ContainerEngine().ContainerExport(context.Background(), args[0], exportOpts)
 }

libpod/container_api.go

@@ -462,7 +462,7 @@ func (c *Container) Unpause() error {
 
 // Export exports a container's root filesystem as a tar archive
 // The archive will be saved as a file at the given path
-func (c *Container) Export(path string) error {
+func (c *Container) Export(out io.Writer) error {
 	if !c.batched {
 		c.lock.Lock()
 		defer c.lock.Unlock()
@@ -477,7 +477,7 @@ func (c *Container) Export(path string) error {
 	}
 
 	defer c.newContainerEvent(events.Mount)
-	return c.export(path)
+	return c.export(out)
 }
 
 // AddArtifact creates and writes to an artifact file for the container

libpod/container_internal.go

@@ -745,7 +745,7 @@ func (c *Container) removeConmonFiles() error {
 	return nil
 }
 
-func (c *Container) export(path string) error {
+func (c *Container) export(out io.Writer) error {
 	mountPoint := c.state.Mountpoint
 	if !c.state.Mounted {
 		containerMount, err := c.runtime.store.Mount(c.ID(), c.config.MountLabel)
@@ -765,13 +765,7 @@ func (c *Container) export(path string) error {
 		return fmt.Errorf("reading container directory %q: %w", c.ID(), err)
 	}
 
-	outFile, err := os.Create(path)
-	if err != nil {
-		return fmt.Errorf("creating file %q: %w", path, err)
-	}
-	defer outFile.Close()
-
-	_, err = io.Copy(outFile, input)
+	_, err = io.Copy(out, input)
 	return err
 }
 

pkg/api/handlers/compat/containers_export.go

@@ -3,7 +3,6 @@ package compat
 import (
 	"fmt"
 	"net/http"
-	"os"
 
 	"github.com/containers/podman/v4/libpod"
 	"github.com/containers/podman/v4/pkg/api/handlers/utils"
@@ -18,25 +17,14 @@ func ExportContainer(w http.ResponseWriter, r *http.Request) {
 		utils.ContainerNotFound(w, name, err)
 		return
 	}
-	tmpfile, err := os.CreateTemp("", "api.tar")
-	if err != nil {
-		utils.Error(w, http.StatusInternalServerError, fmt.Errorf("unable to create tempfile: %w", err))
+
+	// set the correct header
+	w.Header().Set("Content-Type", "application/x-tar")
+	// NOTE: As described in w.Write() it automatically sets the http code to
+	// 200 on first write if no other code was set.
+
+	if err := con.Export(w); err != nil {
+		utils.Error(w, http.StatusInternalServerError, fmt.Errorf("failed to export container: %w", err))
 		return
 	}
-	defer os.Remove(tmpfile.Name())
-	if err := tmpfile.Close(); err != nil {
-		utils.Error(w, http.StatusInternalServerError, fmt.Errorf("unable to close tempfile: %w", err))
-		return
-	}
-	if err := con.Export(tmpfile.Name()); err != nil {
-		utils.Error(w, http.StatusInternalServerError, fmt.Errorf("failed to save image: %w", err))
-		return
-	}
-	rdr, err := os.Open(tmpfile.Name())
-	if err != nil {
-		utils.Error(w, http.StatusInternalServerError, fmt.Errorf("failed to read the exported tarfile: %w", err))
-		return
-	}
-	defer rdr.Close()
-	utils.WriteResponse(w, http.StatusOK, rdr)
 }

pkg/domain/entities/containers.go

@@ -181,7 +181,7 @@ type CommitReport struct {
 }
 
 type ContainerExportOptions struct {
-	Output string
+	Output io.Writer
 }
 
 type CheckpointOptions struct {

pkg/domain/infra/tunnel/containers.go

@@ -355,17 +355,7 @@ func (ic *ContainerEngine) ContainerCommit(ctx context.Context, nameOrID string,
 }
 
 func (ic *ContainerEngine) ContainerExport(ctx context.Context, nameOrID string, options entities.ContainerExportOptions) error {
-	var (
-		err error
-		w   io.Writer
-	)
-	if len(options.Output) > 0 {
-		w, err = os.Create(options.Output)
-		if err != nil {
-			return err
-		}
-	}
-	return containers.Export(ic.ClientCtx, nameOrID, w, nil)
+	return containers.Export(ic.ClientCtx, nameOrID, options.Output, nil)
 }
 
 func (ic *ContainerEngine) ContainerCheckpoint(ctx context.Context, namesOrIds []string, opts entities.CheckpointOptions) ([]*entities.CheckpointReport, error) {

test/apiv2/25-containersMore.at

@@ -51,6 +51,13 @@ like "$output" ".*merged" "Check container mount"
 # Unmount the container
 t POST libpod/containers/foo/unmount 204
 
+# export the container fs to tarball
+
+t GET libpod/containers/foo/export 200
+like "$(<$WORKDIR/curl.headers.out)" ".*"Content-Type\: application/x-tar".*"
+tar_tf=$(tar tf $WORKDIR/curl.result.out)
+like "$tar_tf" ".*bin/cat.*" "fetched tarball: contains bin/cat path"
+
 t DELETE libpod/containers/foo?force=true 200
 
 # Create 3 stopped containers to test containers prune