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volumes.go
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volumes.go
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package daemon
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"strings"
"syscall"
"github.com/docker/docker/archive"
"github.com/docker/docker/daemon/execdriver"
"github.com/docker/docker/pkg/symlink"
)
type Volume struct {
HostPath string
VolPath string
Mode string
isBindMount bool
}
func (v *Volume) isRw() bool {
return v.Mode == "" || strings.ToLower(v.Mode) == "rw"
}
func (v *Volume) isDir() (bool, error) {
stat, err := os.Stat(v.HostPath)
if err != nil {
return false, err
}
return stat.IsDir(), nil
}
func prepareVolumesForContainer(container *Container) error {
if container.Volumes == nil || len(container.Volumes) == 0 {
container.Volumes = make(map[string]string)
container.VolumesRW = make(map[string]bool)
if err := applyVolumesFrom(container); err != nil {
return err
}
}
if err := createVolumes(container); err != nil {
return err
}
return nil
}
func setupMountsForContainer(container *Container) error {
mounts := []execdriver.Mount{
{container.ResolvConfPath, "/etc/resolv.conf", true, true},
}
if container.HostnamePath != "" {
mounts = append(mounts, execdriver.Mount{container.HostnamePath, "/etc/hostname", true, true})
}
if container.HostsPath != "" {
mounts = append(mounts, execdriver.Mount{container.HostsPath, "/etc/hosts", true, true})
}
// 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
for r, v := range container.Volumes {
mounts = append(mounts, execdriver.Mount{v, r, container.VolumesRW[r], false})
}
container.command.Mounts = mounts
return nil
}
func applyVolumesFrom(container *Container) error {
volumesFrom := container.hostConfig.VolumesFrom
if len(volumesFrom) > 0 {
for _, containerSpec := range volumesFrom {
var (
mountRW = true
specParts = strings.SplitN(containerSpec, ":", 2)
)
switch len(specParts) {
case 0:
return fmt.Errorf("Malformed volumes-from specification: %s", containerSpec)
case 2:
switch specParts[1] {
case "ro":
mountRW = false
case "rw": // mountRW is already true
default:
return fmt.Errorf("Malformed volumes-from specification: %s", containerSpec)
}
}
c := container.daemon.Get(specParts[0])
if c == nil {
return fmt.Errorf("Container %s not found. Impossible to mount its volumes", specParts[0])
}
if err := c.Mount(); err != nil {
return fmt.Errorf("Container %s failed to mount. Impossible to mount its volumes", specParts[0])
}
defer c.Unmount()
for volPath, id := range c.Volumes {
if _, exists := container.Volumes[volPath]; exists {
continue
}
pth, err := c.getResourcePath(volPath)
if err != nil {
return err
}
stat, err := os.Stat(pth)
if err != nil {
return err
}
if err := createIfNotExists(pth, stat.IsDir()); err != nil {
return err
}
container.Volumes[volPath] = id
if isRW, exists := c.VolumesRW[volPath]; exists {
container.VolumesRW[volPath] = isRW && mountRW
}
}
}
}
return nil
}
func parseBindVolumeSpec(spec string) (Volume, error) {
var (
arr = strings.Split(spec, ":")
vol Volume
)
vol.isBindMount = true
switch len(arr) {
case 1:
vol.VolPath = spec
vol.Mode = "rw"
case 2:
vol.HostPath = arr[0]
vol.VolPath = arr[1]
vol.Mode = "rw"
case 3:
vol.HostPath = arr[0]
vol.VolPath = arr[1]
vol.Mode = arr[2]
default:
return vol, fmt.Errorf("Invalid volume specification: %s", spec)
}
if !filepath.IsAbs(vol.HostPath) {
return vol, fmt.Errorf("cannot bind mount volume: %s volume paths must be absolute.", vol.HostPath)
}
return vol, nil
}
func getBindMap(container *Container) (map[string]Volume, error) {
var (
// Create the requested bind mounts
volumes = map[string]Volume{}
// Define illegal container destinations
illegalDsts = []string{"/", "."}
)
for _, bind := range container.hostConfig.Binds {
vol, err := parseBindVolumeSpec(bind)
if err != nil {
return volumes, err
}
// Bail if trying to mount to an illegal destination
for _, illegal := range illegalDsts {
if vol.VolPath == illegal {
return nil, fmt.Errorf("Illegal bind destination: %s", vol.VolPath)
}
}
volumes[filepath.Clean(vol.VolPath)] = vol
}
return volumes, nil
}
func createVolumes(container *Container) error {
// Get all the bindmounts
volumes, err := getBindMap(container)
if err != nil {
return err
}
// Get all the rest of the volumes
for volPath := range container.Config.Volumes {
// Make sure the the volume isn't already specified as a bindmount
if _, exists := volumes[volPath]; !exists {
volumes[volPath] = Volume{
VolPath: volPath,
Mode: "rw",
isBindMount: false,
}
}
}
for _, vol := range volumes {
if err = vol.initialize(container); err != nil {
return err
}
}
return nil
}
func createVolumeHostPath(container *Container) (string, error) {
volumesDriver := container.daemon.volumes.Driver()
// Do not pass a container as the parameter for the volume creation.
// The graph driver using the container's information ( Image ) to
// create the parent.
c, err := container.daemon.volumes.Create(nil, "", "", "", "", nil, nil)
if err != nil {
return "", err
}
hostPath, err := volumesDriver.Get(c.ID, "")
if err != nil {
return hostPath, fmt.Errorf("Driver %s failed to get volume rootfs %s: %s", volumesDriver, c.ID, err)
}
return hostPath, nil
}
func (v *Volume) initialize(container *Container) error {
var err error
v.VolPath = filepath.Clean(v.VolPath)
// Do not initialize an existing volume
if _, exists := container.Volumes[v.VolPath]; exists {
return nil
}
// If it's not a bindmount we need to create the dir on the host
if !v.isBindMount {
v.HostPath, err = createVolumeHostPath(container)
if err != nil {
return err
}
}
hostPath, err := filepath.EvalSymlinks(v.HostPath)
if err != nil {
return err
}
// Create the mountpoint
// This is the path to the volume within the container FS
// This differs from `hostPath` in that `hostPath` refers to the place where
// the volume data is actually stored on the host
fullVolPath, err := symlink.FollowSymlinkInScope(filepath.Join(container.basefs, v.VolPath), container.basefs)
if err != nil {
return err
}
container.Volumes[v.VolPath] = hostPath
container.VolumesRW[v.VolPath] = v.isRw()
volIsDir, err := v.isDir()
if err != nil {
return err
}
if err := createIfNotExists(fullVolPath, volIsDir); err != nil {
return err
}
// Do not copy or change permissions if we are mounting from the host
if v.isRw() && !v.isBindMount {
return copyExistingContents(fullVolPath, hostPath)
}
return nil
}
func createIfNotExists(destination string, isDir bool) error {
if _, err := os.Stat(destination); err == nil || !os.IsNotExist(err) {
return nil
}
if isDir {
return os.MkdirAll(destination, 0755)
}
if err := os.MkdirAll(filepath.Dir(destination), 0755); err != nil {
return err
}
f, err := os.OpenFile(destination, os.O_CREATE, 0755)
if err != nil {
return err
}
f.Close()
return nil
}
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 := archive.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 {
var stat syscall.Stat_t
if err := syscall.Stat(source, &stat); 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))
}