dotcloud/docker

package daemon // import "github.com/docker/docker/daemon"

import (
    "context"
    "fmt"
    "io"

    "github.com/docker/docker/api/types/events"
    "github.com/docker/docker/container"
    "github.com/docker/docker/errdefs"
    "github.com/docker/docker/pkg/archive"
    "github.com/docker/docker/pkg/chrootarchive"
)

// ContainerExport writes the contents of the container to the given
// writer. An error is returned if the container cannot be found.
func (daemon *Daemon) ContainerExport(ctx context.Context, name string, out io.Writer) error {
    ctr, err := daemon.GetContainer(name)
    if err != nil {
        return err
    }

    if isWindows && ctr.OS == "windows" {
        return fmt.Errorf("the daemon on this operating system does not support exporting Windows containers")
    }

    if ctr.IsDead() {
        err := fmt.Errorf("You cannot export container %s which is Dead", ctr.ID)
        return errdefs.Conflict(err)
    }

    if ctr.IsRemovalInProgress() {
        err := fmt.Errorf("You cannot export container %s which is being removed", ctr.ID)
        return errdefs.Conflict(err)
    }

    err = daemon.containerExport(ctx, ctr, out)
    if err != nil {
        return fmt.Errorf("Error exporting container %s: %v", name, err)
    }

    return nil
}

func (daemon *Daemon) containerExport(ctx context.Context, container *container.Container, out io.Writer) error {
    err := daemon.imageService.PerformWithBaseFS(ctx, container, func(basefs string) error {
        archv, err := chrootarchive.Tar(basefs, &archive.TarOptions{
            Compression: archive.Uncompressed,
            IDMap:       daemon.idMapping,
        }, basefs)
        if err != nil {
            return err
        }

        // Stream the entire contents of the container (basically a volatile snapshot)
        _, err = io.Copy(out, archv)
        return err
    })
    if err != nil {
        return err
    }
    daemon.LogContainerEvent(container, events.ActionExport)
    return nil
}