// SquashImage creates a new image with the diff of the specified image and the specified parent.
// This new image contains only the layers from it's parent + 1 extra layer which contains the diff of all the layers in between.
// The existing image(s) is not destroyed.
// If no parent is specified, a new image with the diff of all the specified image's layers merged into a new layer that has no parents.
func (daemon *Daemon) SquashImage(id, parent string) (string, error) {
img, err := daemon.imageStore.Get(image.ID(id))
if err != nil {
return "", err
}
var parentImg *image.Image
var parentChainID layer.ChainID
if len(parent) != 0 {
parentImg, err = daemon.imageStore.Get(image.ID(parent))
if err != nil {
return "", errors.Wrap(err, "error getting specified parent layer")
}
parentChainID = parentImg.RootFS.ChainID()
} else {
rootFS := image.NewRootFS()
parentImg = &image.Image{RootFS: rootFS}
}
l, err := daemon.layerStore.Get(img.RootFS.ChainID())
if err != nil {
return "", errors.Wrap(err, "error getting image layer")
}
defer daemon.layerStore.Release(l)
ts, err := l.TarStreamFrom(parentChainID)
if err != nil {
return "", errors.Wrapf(err, "error getting tar stream to parent")
}
defer ts.Close()
newL, err := daemon.layerStore.Register(ts, parentChainID)
if err != nil {
return "", errors.Wrap(err, "error registering layer")
}
defer daemon.layerStore.Release(newL)
var newImage image.Image
newImage = *img
newImage.RootFS = nil
var rootFS image.RootFS
rootFS = *parentImg.RootFS
rootFS.DiffIDs = append(rootFS.DiffIDs, newL.DiffID())
newImage.RootFS = &rootFS
for i, hi := range newImage.History {
if i >= len(parentImg.History) {
hi.EmptyLayer = true
}
newImage.History[i] = hi
}
now := time.Now()
var historyComment string
if len(parent) > 0 {
historyComment = fmt.Sprintf("merge %s to %s", id, parent)
} else {
historyComment = fmt.Sprintf("create new from %s", id)
}
newImage.History = append(newImage.History, image.History{
Created: now,
Comment: historyComment,
})
newImage.Created = now
b, err := json.Marshal(&newImage)
if err != nil {
return "", errors.Wrap(err, "error marshalling image config")
}
newImgID, err := daemon.imageStore.Create(b)
if err != nil {
return "", errors.Wrap(err, "error creating new image after squash")
}
return string(newImgID), nil
}
