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image.go
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image.go
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package docker
import (
"crypto/rand"
"encoding/hex"
"encoding/json"
"fmt"
"github.com/dotcloud/docker/devmapper"
"github.com/dotcloud/docker/utils"
"io"
"io/ioutil"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"syscall"
"time"
)
type Image struct {
ID string `json:"id"`
Parent string `json:"parent,omitempty"`
Comment string `json:"comment,omitempty"`
Created time.Time `json:"created"`
Container string `json:"container,omitempty"`
ContainerConfig Config `json:"container_config,omitempty"`
DockerVersion string `json:"docker_version,omitempty"`
Author string `json:"author,omitempty"`
Config *Config `json:"config,omitempty"`
Architecture string `json:"architecture,omitempty"`
graph *Graph
Size int64
}
func LoadImage(root string) (*Image, error) {
// Load the json data
jsonData, err := ioutil.ReadFile(jsonPath(root))
if err != nil {
return nil, err
}
img := &Image{}
if err := json.Unmarshal(jsonData, img); err != nil {
return nil, err
}
if err := ValidateID(img.ID); err != nil {
return nil, err
}
if buf, err := ioutil.ReadFile(path.Join(root, "layersize")); err != nil {
if !os.IsNotExist(err) {
return nil, err
}
} else {
if size, err := strconv.Atoi(string(buf)); err != nil {
return nil, err
} else {
img.Size = int64(size)
}
}
// Check that the filesystem layer exists
// FIXME: once an image is added into device mapper, the layer is no longer needed
if stat, err := os.Stat(layerPath(root)); err != nil {
if os.IsNotExist(err) {
return nil, fmt.Errorf("Couldn't load image %s: no filesystem layer", img.ID)
}
return nil, err
} else if !stat.IsDir() {
return nil, fmt.Errorf("Couldn't load image %s: %s is not a directory", img.ID, layerPath(root))
}
return img, nil
}
func StoreImage(img *Image, jsonData []byte, layerData Archive, root string) error {
// Check that root doesn't already exist
if _, err := os.Stat(root); err == nil {
return fmt.Errorf("Image %s already exists", img.ID)
} else if !os.IsNotExist(err) {
return err
}
// Store the layer
layer := layerPath(root)
if err := os.MkdirAll(layer, 0755); err != nil {
return err
}
// If layerData is not nil, unpack it into the new layer
if layerData != nil {
start := time.Now()
utils.Debugf("Start untar layer")
if err := Untar(layerData, layer); err != nil {
return err
}
utils.Debugf("Untar time: %vs\n", time.Now().Sub(start).Seconds())
}
// If raw json is provided, then use it
if jsonData != nil {
return ioutil.WriteFile(jsonPath(root), jsonData, 0600)
} else { // Otherwise, unmarshal the image
jsonData, err := json.Marshal(img)
if err != nil {
return err
}
if err := ioutil.WriteFile(jsonPath(root), jsonData, 0600); err != nil {
return err
}
}
return StoreSize(img, root)
}
func StoreSize(img *Image, root string) error {
layer := layerPath(root)
var totalSize int64 = 0
filepath.Walk(layer, func(path string, fileInfo os.FileInfo, err error) error {
totalSize += fileInfo.Size()
return nil
})
img.Size = totalSize
if err := ioutil.WriteFile(path.Join(root, "layersize"), []byte(strconv.Itoa(int(totalSize))), 0600); err != nil {
return nil
}
return nil
}
func layerPath(root string) string {
return path.Join(root, "layer")
}
func jsonPath(root string) string {
return path.Join(root, "json")
}
func mountPath(root string) string {
return path.Join(root, "mount")
}
// TarLayer returns a tar archive of the image's filesystem layer.
func (image *Image) TarLayer(compression Compression) (Archive, error) {
layerPath, err := image.layer()
if err != nil {
return nil, err
}
return Tar(layerPath, compression)
}
type TimeUpdate struct {
path string
time []syscall.Timeval
mode uint32
}
func (image *Image) applyLayer(layer, target string) error {
var updateTimes []TimeUpdate
oldmask := syscall.Umask(0)
defer syscall.Umask(oldmask)
err := filepath.Walk(layer, func(srcPath string, f os.FileInfo, err error) error {
if err != nil {
return err
}
// Skip root
if srcPath == layer {
return nil
}
var srcStat syscall.Stat_t
err = syscall.Lstat(srcPath, &srcStat)
if err != nil {
return err
}
relPath, err := filepath.Rel(layer, srcPath)
if err != nil {
return err
}
targetPath := filepath.Join(target, relPath)
// Skip AUFS metadata
if matched, err := filepath.Match(".wh..wh.*", relPath); err != nil || matched {
if err != nil || !f.IsDir() {
return err
}
return filepath.SkipDir
}
// Find out what kind of modification happened
file := filepath.Base(srcPath)
// If there is a whiteout, then the file was removed
if strings.HasPrefix(file, ".wh.") {
originalFile := file[len(".wh."):]
deletePath := filepath.Join(filepath.Dir(targetPath), originalFile)
err = os.RemoveAll(deletePath)
if err != nil {
return err
}
} else {
var targetStat = &syscall.Stat_t{}
err := syscall.Lstat(targetPath, targetStat)
if err != nil {
if !os.IsNotExist(err) {
return err
}
targetStat = nil
}
if targetStat != nil && !(targetStat.Mode&syscall.S_IFDIR == syscall.S_IFDIR && srcStat.Mode&syscall.S_IFDIR == syscall.S_IFDIR) {
// Unless both src and dest are directories we remove the target and recreate it
// This is a bit wasteful in the case of only a mode change, but that is unlikely
// to matter much
err = os.RemoveAll(targetPath)
if err != nil {
return err
}
targetStat = nil
}
if f.IsDir() {
// Source is a directory
if targetStat == nil {
err = syscall.Mkdir(targetPath, srcStat.Mode&07777)
if err != nil {
return err
}
}
} else if srcStat.Mode&syscall.S_IFLNK == syscall.S_IFLNK {
// Source is symlink
link, err := os.Readlink(srcPath)
if err != nil {
return err
}
err = os.Symlink(link, targetPath)
if err != nil {
return err
}
} else if srcStat.Mode&syscall.S_IFBLK == syscall.S_IFBLK ||
srcStat.Mode&syscall.S_IFCHR == syscall.S_IFCHR ||
srcStat.Mode&syscall.S_IFIFO == syscall.S_IFIFO ||
srcStat.Mode&syscall.S_IFSOCK == syscall.S_IFSOCK {
// Source is special file
err = syscall.Mknod(targetPath, srcStat.Mode, int(srcStat.Rdev))
if err != nil {
return err
}
} else if srcStat.Mode&syscall.S_IFREG == syscall.S_IFREG {
// Source is regular file
fd, err := syscall.Open(targetPath, syscall.O_CREAT|syscall.O_WRONLY, srcStat.Mode&07777)
if err != nil {
return err
}
dstFile := os.NewFile(uintptr(fd), targetPath)
srcFile, err := os.Open(srcPath)
if err != nil {
_ = dstFile.Close()
return err
}
err = CopyFile(dstFile, srcFile)
_ = dstFile.Close()
_ = srcFile.Close()
if err != nil {
return err
}
} else {
return fmt.Errorf("Unknown type for file %s", srcPath)
}
err = syscall.Lchown(targetPath, int(srcStat.Uid), int(srcStat.Gid))
if err != nil {
return err
}
if srcStat.Mode&syscall.S_IFLNK != syscall.S_IFLNK {
err = syscall.Chmod(targetPath, srcStat.Mode&07777)
if err != nil {
return err
}
}
ts := []syscall.Timeval{
syscall.NsecToTimeval(srcStat.Atim.Nano()),
syscall.NsecToTimeval(srcStat.Mtim.Nano()),
}
u := TimeUpdate{
path: targetPath,
time: ts,
mode: srcStat.Mode,
}
// Delay time updates until all other changes done, or it is
// overwritten for directories (by child changes)
updateTimes = append(updateTimes, u)
}
return nil
})
if err != nil {
return err
}
// We do this in reverse order so that children are updated before parents
for i := len(updateTimes) - 1; i >= 0; i-- {
update := updateTimes[i]
O_PATH := 010000000 // Not in syscall yet
var err error
if update.mode&syscall.S_IFLNK == syscall.S_IFLNK {
// Update time on the symlink via O_PATH + futimes(), if supported by the kernel
fd, err := syscall.Open(update.path, syscall.O_RDWR|O_PATH|syscall.O_NOFOLLOW, 0600)
if err == syscall.EISDIR || err == syscall.ELOOP {
// O_PATH not supported by kernel, nothing to do, ignore
} else if err != nil {
return err
} else {
syscall.Futimes(fd, update.time)
syscall.Close(fd)
}
} else {
err = syscall.Utimes(update.path, update.time)
if err != nil {
return err
}
}
}
return nil
}
func (image *Image) ensureImageDevice(devices *devmapper.DeviceSet) error {
if devices.HasInitializedDevice(image.ID) {
return nil
}
if image.Parent != "" && !devices.HasInitializedDevice(image.Parent) {
parentImg, err := image.GetParent()
if err != nil {
return fmt.Errorf("Error while getting parent image: %v", err)
}
err = parentImg.ensureImageDevice(devices)
if err != nil {
return err
}
}
root, err := image.root()
if err != nil {
return err
}
mountDir := mountPath(root)
if err := os.Mkdir(mountDir, 0600); err != nil && !os.IsExist(err) {
return err
}
mounted, err := Mounted(mountDir)
if err == nil && mounted {
utils.Debugf("Image %s is unexpectedly mounted, unmounting...", image.ID)
err = syscall.Unmount(mountDir, 0)
if err != nil {
return err
}
}
if devices.HasDevice(image.ID) {
utils.Debugf("Found non-initialized demove-mapper device for image %s, removing", image.ID)
err = devices.RemoveDevice(image.ID)
if err != nil {
return err
}
}
utils.Debugf("Creating device-mapper device for image id %s", image.ID)
if err := devices.AddDevice(image.ID, image.Parent); err != nil {
utils.Debugf("Error add device: %s", err)
return err
}
if err := devices.MountDevice(image.ID, mountDir, false); err != nil {
utils.Debugf("Error mounting device: %s", err)
devices.RemoveDevice(image.ID)
return err
}
if err = image.applyLayer(layerPath(root), mountDir); err != nil {
utils.Debugf("Error applying layer: %s", err)
devices.UnmountDevice(image.ID, mountDir, true)
devices.RemoveDevice(image.ID)
return err
}
// The docker init layer is conceptually above all other layers, so we apply
// it for every image. This is safe because the layer directory is the
// definition of the image, and the device-mapper device is just a cache
// of it instantiated. Diffs/commit compare the container device with the
// image device, which will then *not* pick up the init layer changes as
// part of the container changes
dockerinitLayer, err := image.getDockerInitLayer()
if err != nil {
devices.UnmountDevice(image.ID, mountDir, true)
devices.RemoveDevice(image.ID)
return err
}
if err := image.applyLayer(dockerinitLayer, mountDir); err != nil {
devices.UnmountDevice(image.ID, mountDir, true)
devices.RemoveDevice(image.ID)
return err
}
if err := devices.UnmountDevice(image.ID, mountDir, true); err != nil {
devices.RemoveDevice(image.ID)
return err
}
devices.SetInitialized(image.ID)
return nil
}
func (image *Image) Mounted(runtime *Runtime, root, rw string) (bool, error) {
return Mounted(root)
}
func (image *Image) Mount(runtime *Runtime, root, rw string, id string) error {
if mounted, _ := image.Mounted(runtime, root, rw); mounted {
return fmt.Errorf("%s is already mounted", root)
}
// Create the target directories if they don't exist
if err := os.Mkdir(root, 0755); err != nil && !os.IsExist(err) {
return err
}
devices, err := runtime.GetDeviceSet()
if err != nil {
return err
}
if err := image.ensureImageDevice(devices); err != nil {
return err
}
if !devices.HasDevice(id) {
utils.Debugf("Creating device %s for container based on image %s", id, image.ID)
err = devices.AddDevice(id, image.ID)
if err != nil {
return err
}
}
utils.Debugf("Mounting container %s at %s for container", id, root)
if err := devices.MountDevice(id, root, false); err != nil {
return err
}
return nil
}
func (image *Image) Unmount(runtime *Runtime, root string, id string) error {
// Try to deactivate the device as generally there is no use for it anymore
devices, err := runtime.GetDeviceSet()
if err != nil {
return err
}
if err = devices.UnmountDevice(id, root, true); err != nil {
return err
}
return nil
}
func (image *Image) Changes(runtime *Runtime, root, rw, id string) ([]Change, error) {
devices, err := runtime.GetDeviceSet()
if err != nil {
return nil, err
}
if err := os.Mkdir(rw, 0755); err != nil && !os.IsExist(err) {
return nil, err
}
wasActivated := devices.HasActivatedDevice(image.ID)
// We re-use rw for the temporary mount of the base image as its
// not used by device-mapper otherwise
err = devices.MountDevice(image.ID, rw, true)
if err != nil {
return nil, err
}
changes, err := ChangesDirs(root, rw)
devices.UnmountDevice(image.ID, rw, !wasActivated)
if err != nil {
return nil, err
}
return changes, nil
}
func (image *Image) ExportChanges(runtime *Runtime, root, rw, id string) (Archive, error) {
changes, err := image.Changes(runtime, root, rw, id)
if err != nil {
return nil, err
}
files := make([]string, 0)
deletions := make([]string, 0)
for _, change := range changes {
if change.Kind == ChangeModify || change.Kind == ChangeAdd {
files = append(files, change.Path)
}
if change.Kind == ChangeDelete {
base := filepath.Base(change.Path)
dir := filepath.Dir(change.Path)
deletions = append(deletions, filepath.Join(dir, ".wh."+base))
}
}
return TarFilter(root, Uncompressed, files, false, deletions)
}
func (image *Image) ShortID() string {
return utils.TruncateID(image.ID)
}
func ValidateID(id string) error {
if id == "" {
return fmt.Errorf("Image id can't be empty")
}
if strings.Contains(id, ":") {
return fmt.Errorf("Invalid character in image id: ':'")
}
return nil
}
func GenerateID() string {
id := make([]byte, 32)
_, err := io.ReadFull(rand.Reader, id)
if err != nil {
panic(err) // This shouldn't happen
}
return hex.EncodeToString(id)
}
// Image includes convenience proxy functions to its graph
// These functions will return an error if the image is not registered
// (ie. if image.graph == nil)
func (img *Image) History() ([]*Image, error) {
var parents []*Image
if err := img.WalkHistory(
func(img *Image) error {
parents = append(parents, img)
return nil
},
); err != nil {
return nil, err
}
return parents, nil
}
// layers returns all the filesystem layers needed to mount an image
// FIXME: @shykes refactor this function with the new error handling
// (I'll do it if I have time tonight, I focus on the rest)
func (img *Image) layers() ([]string, error) {
var list []string
var e error
if err := img.WalkHistory(
func(img *Image) (err error) {
if layer, err := img.layer(); err != nil {
e = err
} else if layer != "" {
list = append(list, layer)
}
return err
},
); err != nil {
return nil, err
} else if e != nil { // Did an error occur inside the handler?
return nil, e
}
if len(list) == 0 {
return nil, fmt.Errorf("No layer found for image %s\n", img.ID)
}
// Inject the dockerinit layer (empty place-holder for mount-binding dockerinit)
if dockerinitLayer, err := img.getDockerInitLayer(); err != nil {
return nil, err
} else {
list = append([]string{dockerinitLayer}, list...)
}
return list, nil
}
func (img *Image) WalkHistory(handler func(*Image) error) (err error) {
currentImg := img
for currentImg != nil {
if handler != nil {
if err := handler(currentImg); err != nil {
return err
}
}
currentImg, err = currentImg.GetParent()
if err != nil {
return fmt.Errorf("Error while getting parent image: %v", err)
}
}
return nil
}
func (img *Image) GetParent() (*Image, error) {
if img.Parent == "" {
return nil, nil
}
if img.graph == nil {
return nil, fmt.Errorf("Can't lookup parent of unregistered image")
}
return img.graph.Get(img.Parent)
}
func (img *Image) getDockerInitLayer() (string, error) {
if img.graph == nil {
return "", fmt.Errorf("Can't lookup dockerinit layer of unregistered image")
}
return img.graph.getDockerInitLayer()
}
func (img *Image) root() (string, error) {
if img.graph == nil {
return "", fmt.Errorf("Can't lookup root of unregistered image")
}
return img.graph.imageRoot(img.ID), nil
}
// Return the path of an image's layer
func (img *Image) layer() (string, error) {
root, err := img.root()
if err != nil {
return "", err
}
return layerPath(root), nil
}
func (img *Image) getParentsSize(size int64) int64 {
parentImage, err := img.GetParent()
if err != nil || parentImage == nil {
return size
}
size += parentImage.Size
return parentImage.getParentsSize(size)
}
// Build an Image object from raw json data
func NewImgJSON(src []byte) (*Image, error) {
ret := &Image{}
utils.Debugf("Json string: {%s}\n", src)
// FIXME: Is there a cleaner way to "purify" the input json?
if err := json.Unmarshal(src, ret); err != nil {
return nil, err
}
return ret, nil
}