package mounts // import "github.com/docker/docker/volume/mounts" import ( "fmt" "os" "path/filepath" "syscall" mounttypes "github.com/docker/docker/api/types/mount" "github.com/docker/docker/pkg/idtools" "github.com/docker/docker/pkg/stringid" "github.com/docker/docker/volume" "github.com/opencontainers/selinux/go-selinux/label" "github.com/pkg/errors" ) // MountPoint is the intersection point between a volume and a container. It // specifies which volume is to be used and where inside a container it should // be mounted. // // Note that this type is embedded in `container.Container` object and persisted to disk. // Changes to this struct need to by synced with on disk state. type MountPoint struct { // Source is the source path of the mount. // E.g. `mount --bind /foo /bar`, `/foo` is the `Source`. Source string // Destination is the path relative to the container root (`/`) to the mount point // It is where the `Source` is mounted to Destination string // RW is set to true when the mountpoint should be mounted as read-write RW bool // Name is the name reference to the underlying data defined by `Source` // e.g., the volume name Name string // Driver is the volume driver used to create the volume (if it is a volume) Driver string // Type of mount to use, see `Type` definitions in github.com/docker/docker/api/types/mount Type mounttypes.Type `json:",omitempty"` // Volume is the volume providing data to this mountpoint. // This is nil unless `Type` is set to `TypeVolume` Volume volume.Volume `json:"-"` // Mode is the comma separated list of options supplied by the user when creating // the bind/volume mount. // Note Mode is not used on Windows Mode string `json:"Relabel,omitempty"` // Originally field was `Relabel`" // Propagation describes how the mounts are propagated from the host into the // mount point, and vice-versa. // See https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt // Note Propagation is not used on Windows Propagation mounttypes.Propagation `json:",omitempty"` // Mount propagation string // Specifies if data should be copied from the container before the first mount // Use a pointer here so we can tell if the user set this value explicitly // This allows us to error out when the user explicitly enabled copy but we can't copy due to the volume being populated CopyData bool `json:"-"` // ID is the opaque ID used to pass to the volume driver. // This should be set by calls to `Mount` and unset by calls to `Unmount` ID string `json:",omitempty"` // Sepc is a copy of the API request that created this mount. Spec mounttypes.Mount // Some bind mounts should not be automatically created. // (Some are auto-created for backwards-compatibility) // This is checked on the API but setting this here prevents race conditions. // where a bind dir existed during validation was removed before reaching the setup code. SkipMountpointCreation bool // Track usage of this mountpoint // Specifically needed for containers which are running and calls to `docker cp` // because both these actions require mounting the volumes. active int } // Cleanup frees resources used by the mountpoint func (m *MountPoint) Cleanup() error { if m.Volume == nil || m.ID == "" { return nil } if err := m.Volume.Unmount(m.ID); err != nil { return errors.Wrapf(err, "error unmounting volume %s", m.Volume.Name()) } m.active-- if m.active == 0 { m.ID = "" } return nil } // Setup sets up a mount point by either mounting the volume if it is // configured, or creating the source directory if supplied. // The, optional, checkFun parameter allows doing additional checking // before creating the source directory on the host. func (m *MountPoint) Setup(mountLabel string, rootIDs idtools.Identity, checkFun func(m *MountPoint) error) (path string, err error) { if m.SkipMountpointCreation { return m.Source, nil } defer func() { if err != nil || !label.RelabelNeeded(m.Mode) { return } var sourcePath string sourcePath, err = filepath.EvalSymlinks(m.Source) if err != nil { path = "" err = errors.Wrapf(err, "error evaluating symlinks from mount source %q", m.Source) return } err = label.Relabel(sourcePath, mountLabel, label.IsShared(m.Mode)) if err == syscall.ENOTSUP { err = nil } if err != nil { path = "" err = errors.Wrapf(err, "error setting label on mount source '%s'", sourcePath) } }() if m.Volume != nil { id := m.ID if id == "" { id = stringid.GenerateRandomID() } path, err := m.Volume.Mount(id) if err != nil { return "", errors.Wrapf(err, "error while mounting volume '%s'", m.Source) } m.ID = id m.active++ return path, nil } if len(m.Source) == 0 { return "", fmt.Errorf("Unable to setup mount point, neither source nor volume defined") } if m.Type == mounttypes.TypeBind { // Before creating the source directory on the host, invoke checkFun if it's not nil. One of // the use case is to forbid creating the daemon socket as a directory if the daemon is in // the process of shutting down. if checkFun != nil { if err := checkFun(m); err != nil { return "", err } } // idtools.MkdirAllNewAs() produces an error if m.Source exists and is a file (not a directory) // also, makes sure that if the directory is created, the correct remapped rootUID/rootGID will own it if err := idtools.MkdirAllAndChownNew(m.Source, 0755, rootIDs); err != nil { if perr, ok := err.(*os.PathError); ok { if perr.Err != syscall.ENOTDIR { return "", errors.Wrapf(err, "error while creating mount source path '%s'", m.Source) } } } } return m.Source, nil } // Path returns the path of a volume in a mount point. func (m *MountPoint) Path() string { if m.Volume != nil { return m.Volume.Path() } return m.Source } func errInvalidMode(mode string) error { return errors.Errorf("invalid mode: %v", mode) } func errInvalidSpec(spec string) error { return errors.Errorf("invalid volume specification: '%s'", spec) }