Documentation
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Overview ¶
Package layer is package for managing read-only and read-write mounts on the union file system driver. Read-only mounts are referenced using a content hash and are protected from mutation in the exposed interface. The tar format is used to create read-only layers and export both read-only and writable layers. The exported tar data for a read-only layer should match the tar used to create the layer.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrLayerDoesNotExist is used when an operation is // attempted on a layer which does not exist. ErrLayerDoesNotExist = errors.New("layer does not exist") // ErrLayerNotRetained is used when a release is // attempted on a layer which is not retained. ErrLayerNotRetained = errors.New("layer not retained") // ErrMountDoesNotExist is used when an operation is // attempted on a mount layer which does not exist. ErrMountDoesNotExist = errors.New("mount does not exist") // ErrMountNameConflict is used when a mount is attempted // to be created but there is already a mount with the name // used for creation. ErrMountNameConflict = errors.New("mount already exists with name") // ErrMaxDepthExceeded is used when a layer is attempted // to be created which would result in a layer depth // greater than the 125 max. ErrMaxDepthExceeded = errors.New("max depth exceeded") )
var EmptyLayer = &emptyLayer{}
EmptyLayer is a layer that corresponds to empty tar.
Functions ¶
func ReleaseAndLog ¶
ReleaseAndLog releases the provided layer from the given layer store, logging any error and release metadata
Types ¶
type ChainID ¶
type ChainID = digest.Digest
ChainID is the content-addressable ID of a layer.
func CreateChainID
deprecated
CreateChainID returns ID for a layerDigest slice.
Deprecated: use identity.ChainID.
type CreateRWLayerOpts ¶
CreateRWLayerOpts contains optional arguments to be passed to CreateRWLayer
type DescribableStore ¶
type DescribableStore interface {
RegisterWithDescriptor(io.Reader, ChainID, distribution.Descriptor) (Layer, error)
}
DescribableStore represents a layer store capable of storing descriptors for layers.
type DiffID ¶
type DiffID = digest.Digest
DiffID is the hash of an individual layer tar.
const DigestSHA256EmptyTar DiffID = "sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef"
DigestSHA256EmptyTar is the canonical sha256 digest of empty tar file - (1024 NULL bytes)
type Layer ¶
type Layer interface {
TarStreamer
// TarStreamFrom returns a tar archive stream for all the layer chain with
// arbitrary depth.
TarStreamFrom(ChainID) (io.ReadCloser, error)
// ChainID returns the content hash of the entire layer chain. The hash
// chain is made up of DiffID of top layer and all of its parents.
ChainID() ChainID
// DiffID returns the content hash of the layer
// tar stream used to create this layer.
DiffID() DiffID
// Parent returns the next layer in the layer chain.
Parent() Layer
// Size returns the size of the entire layer chain. The size
// is calculated from the total size of all files in the layers.
Size() int64
// DiffSize returns the size difference of the top layer
// from parent layer.
DiffSize() int64
// Metadata returns the low level storage metadata associated
// with layer.
Metadata() (map[string]string, error)
}
Layer represents a read-only layer
type Metadata ¶
type Metadata struct {
// ChainID is the content hash of the layer
ChainID ChainID
// DiffID is the hash of the tar data used to
// create the layer
DiffID DiffID
// Size is the size of the layer and all parents
Size int64
// DiffSize is the size of the top layer
DiffSize int64
}
Metadata holds information about a read-only layer
type MountInit ¶
MountInit is a function to initialize a writable mount. Changes made here will not be included in the Tar stream of the RWLayer.
type RWLayer ¶
type RWLayer interface {
TarStreamer
// Name of mounted layer
Name() string
// Parent returns the layer which the writable
// layer was created from.
Parent() Layer
// Mount mounts the RWLayer and returns the filesystem path
// to the writable layer.
Mount(mountLabel string) (string, error)
// Unmount unmounts the RWLayer. This should be called
// for every mount. If there are multiple mount calls
// this operation will only decrement the internal mount counter.
Unmount() error
// Size represents the size of the writable layer
// as calculated by the total size of the files
// changed in the mutable layer.
Size() (int64, error)
// Changes returns the set of changes for the mutable layer
// from the base layer.
Changes() ([]archive.Change, error)
// Metadata returns the low level metadata for the mutable layer
Metadata() (map[string]string, error)
// ApplyDiff applies the diff to the RW layer
ApplyDiff(diff io.Reader) (int64, error)
}
RWLayer represents a layer which is read and writable
type Store ¶
type Store interface {
Register(io.Reader, ChainID) (Layer, error)
Get(ChainID) (Layer, error)
Map() map[ChainID]Layer
Release(Layer) ([]Metadata, error)
CreateRWLayer(id string, parent ChainID, opts *CreateRWLayerOpts) (RWLayer, error)
GetRWLayer(id string) (RWLayer, error)
GetMountID(id string) (string, error)
ReleaseRWLayer(RWLayer) ([]Metadata, error)
Cleanup() error
DriverStatus() [][2]string
DriverName() string
}
Store represents a backend for managing both read-only and read-write layers.
func NewStoreFromOptions ¶
func NewStoreFromOptions(options StoreOptions) (Store, error)
NewStoreFromOptions creates a new Store instance
type StoreOptions ¶
type StoreOptions struct {
Root string
GraphDriver string
GraphDriverOptions []string
IDMapping user.IdentityMapping
}
StoreOptions are the options used to create a new Store instance
type TarStreamer ¶
type TarStreamer interface {
// TarStream returns a tar archive stream
// for the contents of a layer.
TarStream() (io.ReadCloser, error)
}
TarStreamer represents an object which may have its contents exported as a tar stream.
Source Files