overlay

type Bundle ¶

type Bundle struct {
	// contains filtered or unexported fields
}

An Bundle is an OCI runtime bundle. Its root filesystem is a temporary overlay atop its image's cached layers.

func BootstrapBundle(path string, parentLayerPaths []string) (Bundle, error)

func (b Bundle) Cleanup() error

func (b Bundle) Path() string

type BundleBootstrapper ¶

type BundleBootstrapper interface {
	Bootstrap(path string, parentLayerPaths []string) (Bundle, error)
}

A BundleBootstrapper bootstraps a bundle by creating and mounting its rootfs.

type BundleBootstrapperFn ¶

type BundleBootstrapperFn func(path string, parentLayerPaths []string) (Bundle, error)

A BundleBootstrapperFn bootstraps a bundle by creating and mounting its rootfs.

func (fn BundleBootstrapperFn) Bootstrap(path string, parentLayerPaths []string) (Bundle, error)

type CachingBundler ¶

type CachingBundler struct {
	// contains filtered or unexported fields
}

An CachingBundler stores OCI containers, images, and layers. When asked to bundle a container for a new image the CachingBundler will extract and cache the image's layers as files on disk. The container's root filesystem is then created as an overlay atop the image's layers. The upper layer of this overlay is stored in memory on a tmpfs, and discarded once the container has finished running.

func NewCachingBundler(root string) (*CachingBundler, error)

func (c *CachingBundler) Bundle(ctx context.Context, i ociv1.Image, id string, o ...spec.Option) (store.Bundle, error)

type CachingLayerResolver ¶

type CachingLayerResolver struct {
	// contains filtered or unexported fields
}

A CachingLayerResolver resolves an OCI layer to an overlay compatible directory on disk. The directory is created the first time a layer is resolved; subsequent calls return the cached directory.

func NewCachingLayerResolver(root string) (*CachingLayerResolver, error)

func (s *CachingLayerResolver) Resolve(ctx context.Context, l ociv1.Layer, parents ...ociv1.Layer) (string, error)

type LayerResolver ¶

type LayerResolver interface {
	// Resolve the supplied layer to a path suitable for use as a lower dir.
	Resolve(ctx context.Context, l ociv1.Layer, parents ...ociv1.Layer) (string, error)
}

An LayerResolver resolves the supplied layer to a path suitable for use as an overlayfs lower directory.

type LayerWorkdir ¶

type LayerWorkdir struct {
	// contains filtered or unexported fields
}

A LayerWorkdir is a temporary directory used to produce an overlayfs layer from an OCI layer by applying the OCI layer to a temporary overlay mount. It's not possible to _directly_ create overlay whiteout files in an unprivileged user namespace because doing so requires CAP_MKNOD in the 'root' or 'initial' user namespace - whiteout files are actually character devices per "whiteouts and opaque directories" at https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt

We can however create overlay whiteout files indirectly by creating an overlay where the parent OCI layers are the lower overlayfs layers, and applying the layer to be cached to said fs. Doing so will produce an upper overlayfs layer that we can cache. This layer will be a valid lower layer (complete with overlay whiteout files) for either subsequent layers from the OCI image, or the final container root filesystem layer.

func NewLayerWorkdir(dir, digest string, parentLayerPaths []string, o ...NewLayerWorkdirOption) (LayerWorkdir, error)

func (d LayerWorkdir) ApplyPath() string

func (d LayerWorkdir) Cleanup() error

func (d LayerWorkdir) ResultPath() string

type Mount ¶

type Mount interface {
	Mount() error
	Unmount() error
}

A Mount of a filesystem.

func DefaultNewOverlayMount(path string, parentLayerPaths []string) Mount

type NewLayerWorkdirOption ¶

type NewLayerWorkdirOption func(*WorkDirOptions)

NewLayerWorkdirOption configures how a new layer workdir is created.

func WithNewOverlayMountFn(fn NewOverlayMountFn) NewLayerWorkdirOption

type NewOverlayMountFn ¶

type NewOverlayMountFn func(path string, parentLayerPaths []string) Mount

NewOverlayMountFn creates an overlay mount.

type OverlayMount ¶

type OverlayMount struct {
	Mountpoint string
	Lower      []string
	Upper      string
	Work       string
}

An OverlayMount represents a mount of type overlay.

func (m OverlayMount) Mount() error

func (m OverlayMount) Unmount() error

type RuntimeSpecWriter ¶

type RuntimeSpecWriter interface {
	// Write and write an OCI runtime spec to the supplied path.
	Write(path string, o ...spec.Option) error
}

A RuntimeSpecWriter writes an OCI runtime spec to the supplied path.

type RuntimeSpecWriterFn ¶

type RuntimeSpecWriterFn func(path string, o ...spec.Option) error

A RuntimeSpecWriterFn allows a function to satisfy RuntimeSpecCreator.

func (fn RuntimeSpecWriterFn) Write(path string, o ...spec.Option) error

type TarballApplicator ¶

type TarballApplicator interface {
	// Apply the supplied tarball - an OCI filesystem layer - to the supplied
	// root directory. Applying all of an image's layers, in the correct order,
	// should produce the image's "flattened" filesystem.
	Apply(ctx context.Context, tb io.Reader, root string) error
}

A TarballApplicator applies (i.e. extracts) an OCI layer tarball. https://github.com/opencontainers/image-spec/blob/v1.0/layer.md

type TmpFSMount ¶

type TmpFSMount struct {
	Mountpoint string
}

A TmpFSMount represents a mount of type tmpfs.

func (m TmpFSMount) Mount() error

func (m TmpFSMount) Unmount() error

type WorkDirOptions ¶

type WorkDirOptions struct {
	NewOverlayMount NewOverlayMountFn
}

WorkDirOptions configure how a new layer workdir is created.