daemon/volumes_unix.go
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 // +build !windows
 
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 package daemon // import "github.com/docker/docker/daemon"
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 import (
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 	"fmt"
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 	"os"
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 	"sort"
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 	"strconv"
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 	"strings"
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 	"github.com/docker/docker/container"
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 	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/mount"
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 	volumemounts "github.com/docker/docker/volume/mounts"
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 )
 
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 // setupMounts iterates through each of the mount points for a container and
 // calls Setup() on each. It also looks to see if is a network mount such as
 // /etc/resolv.conf, and if it is not, appends it to the array of mounts.
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 func (daemon *Daemon) setupMounts(c *container.Container) ([]container.Mount, error) {
 	var mounts []container.Mount
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 	// TODO: tmpfs mounts should be part of Mountpoints
 	tmpfsMounts := make(map[string]bool)
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 	tmpfsMountInfo, err := c.TmpfsMounts()
 	if err != nil {
 		return nil, err
 	}
 	for _, m := range tmpfsMountInfo {
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 		tmpfsMounts[m.Destination] = true
 	}
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 	for _, m := range c.MountPoints {
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 		if tmpfsMounts[m.Destination] {
 			continue
 		}
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 		if err := daemon.lazyInitializeVolume(c.ID, m); err != nil {
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 			return nil, err
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 		}
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 		// If the daemon is being shutdown, we should not let a container start if it is trying to
 		// mount the socket the daemon is listening on. During daemon shutdown, the socket
 		// (/var/run/docker.sock by default) doesn't exist anymore causing the call to m.Setup to
 		// create at directory instead. This in turn will prevent the daemon to restart.
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 		checkfunc := func(m *volumemounts.MountPoint) error {
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 			if _, exist := daemon.hosts[m.Source]; exist && daemon.IsShuttingDown() {
 				return fmt.Errorf("Could not mount %q to container while the daemon is shutting down", m.Source)
 			}
 			return nil
 		}
 
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 		path, err := m.Setup(c.MountLabel, daemon.idMappings.RootPair(), checkfunc)
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 		if err != nil {
 			return nil, err
 		}
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 		if !c.TrySetNetworkMount(m.Destination, path) {
 			mnt := container.Mount{
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 				Source:      path,
 				Destination: m.Destination,
 				Writable:    m.RW,
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 				Propagation: string(m.Propagation),
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 			}
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 			if m.Volume != nil {
 				attributes := map[string]string{
 					"driver":      m.Volume.DriverName(),
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 					"container":   c.ID,
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 					"destination": m.Destination,
 					"read/write":  strconv.FormatBool(m.RW),
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 					"propagation": string(m.Propagation),
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 				}
 				daemon.LogVolumeEvent(m.Volume.Name(), "mount", attributes)
 			}
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 			mounts = append(mounts, mnt)
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 		}
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 	}
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 	mounts = sortMounts(mounts)
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 	netMounts := c.NetworkMounts()
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 	// if we are going to mount any of the network files from container
 	// metadata, the ownership must be set properly for potential container
 	// remapped root (user namespaces)
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 	rootIDs := daemon.idMappings.RootPair()
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 	for _, mount := range netMounts {
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 		// we should only modify ownership of network files within our own container
 		// metadata repository. If the user specifies a mount path external, it is
 		// up to the user to make sure the file has proper ownership for userns
 		if strings.Index(mount.Source, daemon.repository) == 0 {
 			if err := os.Chown(mount.Source, rootIDs.UID, rootIDs.GID); err != nil {
 				return nil, err
 			}
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 		}
 	}
 	return append(mounts, netMounts...), nil
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 }
 
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 // sortMounts sorts an array of mounts in lexicographic order. This ensure that
 // when mounting, the mounts don't shadow other mounts. For example, if mounting
 // /etc and /etc/resolv.conf, /etc/resolv.conf must not be mounted first.
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 func sortMounts(m []container.Mount) []container.Mount {
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 	sort.Sort(mounts(m))
 	return m
 }
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 // setBindModeIfNull is platform specific processing to ensure the
 // shared mode is set to 'z' if it is null. This is called in the case
 // of processing a named volume and not a typical bind.
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 func setBindModeIfNull(bind *volumemounts.MountPoint) {
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 	if bind.Mode == "" {
 		bind.Mode = "z"
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 	}
 }
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 func (daemon *Daemon) mountVolumes(container *container.Container) error {
 	mounts, err := daemon.setupMounts(container)
 	if err != nil {
 		return err
 	}
 
 	for _, m := range mounts {
 		dest, err := container.GetResourcePath(m.Destination)
 		if err != nil {
 			return err
 		}
 
 		var stat os.FileInfo
 		stat, err = os.Stat(m.Source)
 		if err != nil {
 			return err
 		}
 		if err = fileutils.CreateIfNotExists(dest, stat.IsDir()); err != nil {
 			return err
 		}
 
 		opts := "rbind,ro"
 		if m.Writable {
 			opts = "rbind,rw"
 		}
 
 		if err := mount.Mount(m.Source, dest, bindMountType, opts); err != nil {
 			return err
 		}
 
 		// mountVolumes() seems to be called for temporary mounts
 		// outside the container. Soon these will be unmounted with
 		// lazy unmount option and given we have mounted the rbind,
 		// all the submounts will propagate if these are shared. If
 		// daemon is running in host namespace and has / as shared
 		// then these unmounts will propagate and unmount original
 		// mount as well. So make all these mounts rprivate.
 		// Do not use propagation property of volume as that should
 		// apply only when mounting happen inside the container.
 		if err := mount.MakeRPrivate(dest); err != nil {
 			return err
 		}
 	}
 
 	return nil
 }