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moby--moby/daemon/volumes.go

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package daemon
import (
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"sort"
"strings"
log "github.com/Sirupsen/logrus"
"github.com/docker/docker/daemon/execdriver"
"github.com/docker/docker/pkg/chrootarchive"
"github.com/docker/docker/pkg/symlink"
"github.com/docker/docker/pkg/system"
"github.com/docker/docker/volumes"
)
type Mount struct {
MountToPath string
container *Container
volume *volumes.Volume
Writable bool
copyData bool
from *Container
isBind bool
}
func (mnt *Mount) Export(resource string) (io.ReadCloser, error) {
var name string
if resource == mnt.MountToPath[1:] {
name = filepath.Base(resource)
}
path, err := filepath.Rel(mnt.MountToPath[1:], resource)
if err != nil {
return nil, err
}
return mnt.volume.Export(path, name)
}
func (container *Container) prepareVolumes() error {
if container.Volumes == nil || len(container.Volumes) == 0 {
container.Volumes = make(map[string]string)
container.VolumesRW = make(map[string]bool)
}
return container.createVolumes()
}
// sortedVolumeMounts returns the list of container volume mount points sorted in lexicographic order
func (container *Container) sortedVolumeMounts() []string {
var mountPaths []string
for path := range container.Volumes {
mountPaths = append(mountPaths, path)
}
sort.Strings(mountPaths)
return mountPaths
}
func (container *Container) createVolumes() error {
mounts, err := container.parseVolumeMountConfig()
if err != nil {
return err
}
for _, mnt := range mounts {
if err := mnt.initialize(); err != nil {
return err
}
}
// On every start, this will apply any new `VolumesFrom` entries passed in via HostConfig, which may override volumes set in `create`
return container.applyVolumesFrom()
}
func (m *Mount) initialize() error {
// No need to initialize anything since it's already been initialized
if hostPath, exists := m.container.Volumes[m.MountToPath]; exists {
// If this is a bind-mount/volumes-from, maybe it was passed in at start instead of create
// We need to make sure bind-mounts/volumes-from passed on start can override existing ones.
if (!m.volume.IsBindMount && !m.isBind) && m.from == nil {
return nil
}
if m.volume.Path == hostPath {
return nil
}
// Make sure we remove these old volumes we don't actually want now.
// Ignore any errors here since this is just cleanup, maybe someone volumes-from'd this volume
if v := m.container.daemon.volumes.Get(hostPath); v != nil {
v.RemoveContainer(m.container.ID)
m.container.daemon.volumes.Delete(v.Path)
}
}
// This is the full path to container fs + mntToPath
containerMntPath, err := symlink.FollowSymlinkInScope(filepath.Join(m.container.basefs, m.MountToPath), m.container.basefs)
if err != nil {
return err
}
m.container.VolumesRW[m.MountToPath] = m.Writable
m.container.Volumes[m.MountToPath] = m.volume.Path
m.volume.AddContainer(m.container.ID)
if m.Writable && m.copyData {
// Copy whatever is in the container at the mntToPath to the volume
copyExistingContents(containerMntPath, m.volume.Path)
}
return nil
}
func (container *Container) VolumePaths() map[string]struct{} {
var paths = make(map[string]struct{})
for _, path := range container.Volumes {
paths[path] = struct{}{}
}
return paths
}
func (container *Container) registerVolumes() {
for path := range container.VolumePaths() {
if v := container.daemon.volumes.Get(path); v != nil {
v.AddContainer(container.ID)
continue
}
// if container was created with an old daemon, this volume may not be registered so we need to make sure it gets registered
writable := true
if rw, exists := container.VolumesRW[path]; exists {
writable = rw
}
v, err := container.daemon.volumes.FindOrCreateVolume(path, writable)
if err != nil {
log.Debugf("error registering volume %s: %v", path, err)
continue
}
v.AddContainer(container.ID)
}
}
func (container *Container) derefVolumes() {
for path := range container.VolumePaths() {
vol := container.daemon.volumes.Get(path)
if vol == nil {
log.Debugf("Volume %s was not found and could not be dereferenced", path)
continue
}
vol.RemoveContainer(container.ID)
}
}
func (container *Container) parseVolumeMountConfig() (map[string]*Mount, error) {
var mounts = make(map[string]*Mount)
// Get all the bind mounts
for _, spec := range container.hostConfig.Binds {
path, mountToPath, writable, err := parseBindMountSpec(spec)
if err != nil {
return nil, err
}
// Check if a bind mount has already been specified for the same container path
if m, exists := mounts[mountToPath]; exists {
return nil, fmt.Errorf("Duplicate volume %q: %q already in use, mounted from %q", path, mountToPath, m.volume.Path)
}
// Check if a volume already exists for this and use it
vol, err := container.daemon.volumes.FindOrCreateVolume(path, writable)
if err != nil {
return nil, err
}
mounts[mountToPath] = &Mount{
container: container,
volume: vol,
MountToPath: mountToPath,
Writable: writable,
isBind: true, // in case the volume itself is a normal volume, but is being mounted in as a bindmount here
}
}
// Get the rest of the volumes
for path := range container.Config.Volumes {
// Check if this is already added as a bind-mount
path = filepath.Clean(path)
if _, exists := mounts[path]; exists {
continue
}
// Check if this has already been created
if _, exists := container.Volumes[path]; exists {
continue
}
if stat, err := os.Stat(filepath.Join(container.basefs, path)); err == nil {
if !stat.IsDir() {
return nil, fmt.Errorf("file exists at %s, can't create volume there")
}
}
vol, err := container.daemon.volumes.FindOrCreateVolume("", true)
if err != nil {
return nil, err
}
mounts[path] = &Mount{
container: container,
MountToPath: path,
volume: vol,
Writable: true,
copyData: true,
}
}
return mounts, nil
}
func parseBindMountSpec(spec string) (string, string, bool, error) {
var (
path, mountToPath string
writable bool
arr = strings.Split(spec, ":")
)
switch len(arr) {
case 2:
path = arr[0]
mountToPath = arr[1]
writable = true
case 3:
path = arr[0]
mountToPath = arr[1]
writable = validMountMode(arr[2]) && arr[2] == "rw"
default:
return "", "", false, fmt.Errorf("Invalid volume specification: %s", spec)
}
if !filepath.IsAbs(path) {
return "", "", false, fmt.Errorf("cannot bind mount volume: %s volume paths must be absolute.", path)
}
path = filepath.Clean(path)
mountToPath = filepath.Clean(mountToPath)
return path, mountToPath, writable, nil
}
func parseVolumesFromSpec(spec string) (string, string, error) {
specParts := strings.SplitN(spec, ":", 2)
if len(specParts) == 0 {
return "", "", fmt.Errorf("malformed volumes-from specification: %s", spec)
}
var (
id = specParts[0]
mode = "rw"
)
if len(specParts) == 2 {
mode = specParts[1]
if !validMountMode(mode) {
return "", "", fmt.Errorf("invalid mode for volumes-from: %s", mode)
}
}
return id, mode, nil
}
func (container *Container) applyVolumesFrom() error {
volumesFrom := container.hostConfig.VolumesFrom
if len(volumesFrom) > 0 && container.AppliedVolumesFrom == nil {
container.AppliedVolumesFrom = make(map[string]struct{})
}
mountGroups := make(map[string][]*Mount)
for _, spec := range volumesFrom {
id, mode, err := parseVolumesFromSpec(spec)
if err != nil {
return err
}
if _, exists := container.AppliedVolumesFrom[id]; exists {
// Don't try to apply these since they've already been applied
continue
}
c, err := container.daemon.Get(id)
if err != nil {
return fmt.Errorf("Could not apply volumes of non-existent container %q.", id)
}
var (
fromMounts = c.VolumeMounts()
mounts []*Mount
)
for _, mnt := range fromMounts {
mnt.Writable = mnt.Writable && (mode == "rw")
mounts = append(mounts, mnt)
}
mountGroups[id] = mounts
}
for id, mounts := range mountGroups {
for _, mnt := range mounts {
mnt.from = mnt.container
mnt.container = container
if err := mnt.initialize(); err != nil {
return err
}
}
container.AppliedVolumesFrom[id] = struct{}{}
}
return nil
}
func validMountMode(mode string) bool {
validModes := map[string]bool{
"rw": true,
"ro": true,
}
return validModes[mode]
}
func (container *Container) setupMounts() error {
mounts := []execdriver.Mount{}
// Mount user specified volumes
// Note, these are not private because you may want propagation of (un)mounts from host
// volumes. For instance if you use -v /usr:/usr and the host later mounts /usr/share you
// want this new mount in the container
// These mounts must be ordered based on the length of the path that it is being mounted to (lexicographic)
for _, path := range container.sortedVolumeMounts() {
mounts = append(mounts, execdriver.Mount{
Source: container.Volumes[path],
Destination: path,
Writable: container.VolumesRW[path],
})
}
if container.ResolvConfPath != "" {
mounts = append(mounts, execdriver.Mount{Source: container.ResolvConfPath, Destination: "/etc/resolv.conf", Writable: true, Private: true})
}
if container.HostnamePath != "" {
mounts = append(mounts, execdriver.Mount{Source: container.HostnamePath, Destination: "/etc/hostname", Writable: true, Private: true})
}
if container.HostsPath != "" {
mounts = append(mounts, execdriver.Mount{Source: container.HostsPath, Destination: "/etc/hosts", Writable: true, Private: true})
}
container.command.Mounts = mounts
return nil
}
func (container *Container) VolumeMounts() map[string]*Mount {
mounts := make(map[string]*Mount)
for mountToPath, path := range container.Volumes {
if v := container.daemon.volumes.Get(path); v != nil {
mounts[mountToPath] = &Mount{volume: v, container: container, MountToPath: mountToPath, Writable: container.VolumesRW[mountToPath]}
}
}
return mounts
}
func copyExistingContents(source, destination string) error {
volList, err := ioutil.ReadDir(source)
if err != nil {
return err
}
if len(volList) > 0 {
srcList, err := ioutil.ReadDir(destination)
if err != nil {
return err
}
if len(srcList) == 0 {
// If the source volume is empty copy files from the root into the volume
if err := chrootarchive.CopyWithTar(source, destination); err != nil {
return err
}
}
}
return copyOwnership(source, destination)
}
// copyOwnership copies the permissions and uid:gid of the source file
// into the destination file
func copyOwnership(source, destination string) error {
stat, err := system.Stat(source)
if err != nil {
return err
}
if err := os.Chown(destination, int(stat.Uid()), int(stat.Gid())); err != nil {
return err
}
return os.Chmod(destination, os.FileMode(stat.Mode()))
}