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+% CONTAINERS-TRANSPORTS 5 Containers Transports Man Page
+% Valentin Rothberg
+% April 2019
+
+## NAME
+
+containers-transports - description of supported transports for copying and storing container images
+
+## DESCRIPTION
+
+Tools which use the containers/image library, including skopeo(1), buildah(1), podman(1), all share a common syntax for referring to container images in various locations.
+The general form of the syntax is _transport:details_, where details are dependent on the specified transport, which are documented below.
+
+The semantics of the image names ultimately depend on the environment where
+they are evaluated. For example: if evaluated on a remote server, image names
+might refer to paths on that server; relative paths are relative to the current
+directory of the image consumer.
+
+<!-- atomic: is deprecated and not documented here. -->
+
+### **containers-storage**:[**[**storage-specifier**]**]{image-id|docker-reference[@image-id]}
+
+An image located in a local containers storage.
+The format of _docker-reference_ is described in detail in the **docker** transport.
+
+The _storage-specifier_ allows for referencing storage locations on the file system and has the format `[[driver@]root[+run-root][:options]]` where the optional `driver` refers to the storage driver (e.g., overlay or btrfs) and where `root` is an absolute path to the storage's root directory.
+The optional `run-root` can be used to specify the run directory of the storage where all temporary writable content is stored.
+The optional `options` are a comma-separated list of driver-specific options.
+Please refer to containers-storage.conf(5) for further information on the drivers and supported options.
+
+### **dir:**_path_
+
+An existing local directory _path_ storing the manifest, layer tarballs and signatures as individual files.
+This is a non-standardized format, primarily useful for debugging or noninvasive container inspection.
+
+### **docker://**_docker-reference_
+
+An image in a registry implementing the "Docker Registry HTTP API V2".
+By default, uses the authorization state in `$XDG_RUNTIME_DIR/containers/auth.json`, which is set using podman-login(1).
+If the authorization state is not found there, `$HOME/.docker/config.json` is checked, which is set using docker-login(1).
+The containers-registries.conf(5) further allows for configuring various settings of a registry.
+
+Note that a _docker-reference_ has the following format: _name_[**:**_tag_ | **@**_digest_].
+While the docker transport does not support both a tag and a digest at the same time some formats like containers-storage do.
+Digests can also be used in an image destination as long as the manifest matches the provided digest.
+
+The docker transport supports pushing images without a tag or digest to a registry when the image name is suffixed with **@@unknown-digest@@**. The _name_**@@unknown-digest@@** reference format cannot be used with a reference that has a tag or digest.
+The digest of images can be explored with skopeo-inspect(1).
+
+If `name` does not contain a slash, it is treated as `docker.io/library/name`.
+Otherwise, the component before the first slash is checked if it is recognized as a `hostname[:port]` (i.e., it contains either a . or a :, or the component is exactly localhost).
+If the first component of name is not recognized as a `hostname[:port]`, `name` is treated as `docker.io/name`.
+
+### **docker-archive:**_path[:{docker-reference|@source-index}]_
+
+An image is stored in the docker-save(1) formatted file.
+_docker-reference_ must not contain a digest.
+Alternatively, for reading archives, @_source-index_ is a zero-based index in archive manifest
+(to access untagged images).
+If neither _docker-reference_ nor @_source_index is specified when reading an archive, the archive must contain exactly one image.
+
+The _path_ can refer to a stream, e.g. `docker-archive:/dev/stdin`.
+
+### **docker-daemon:**_docker-reference|algo:digest_
+
+An image stored in the docker daemon's internal storage.
+The image must be specified as a _docker-reference_ or in an alternative _algo:digest_ format when being used as an image source.
+The _algo:digest_ refers to the image ID reported by docker-inspect(1).
+
+### **oci:**_path[:reference]_
+
+An image in a directory structure compliant with the "Open Container Image Layout Specification" at _path_.
+
+The _path_ value terminates at the first `:` character; any further `:` characters are not separators, but a part of _reference_.
+The _reference_ is used to set, or match, the `org.opencontainers.image.ref.name` annotation in the top-level index.
+If _reference_ is not specified when reading an image, the directory must contain exactly one image.
+
+### **oci-archive:**_path[:reference]_
+
+An image in a tar(1) archive with contents compliant with the "Open Container Image Layout Specification" at _path_.
+
+The _path_ value terminates at the first `:` character; any further `:` characters are not separators, but a part of _reference_.
+The _reference_ is used to set, or match, the `org.opencontainers.image.ref.name` annotation in the top-level index.
+If _reference_ is not specified when reading an archive, the archive must contain exactly one image.
+
+### **ostree:**_docker-reference[@/absolute/repo/path]_
+
+An image in the local ostree(1) repository.
+_/absolute/repo/path_ defaults to _/ostree/repo_.
+
+### **sif:**_path_
+
+An image using the Singularity image format at _path_.
+
+Only reading images is supported, and not all scripts can be represented in the OCI format.
+
+<!-- tarball: can only usefully be used from Go callers who call tarballReference.ConfigUpdate, and is not documented here. -->
+
+## Examples
+
+The following examples demonstrate how some of the containers transports can be used.
+The examples use skopeo-copy(1) for copying container images.
+
+**Copying an image from one registry to another**:
+```
+$ skopeo copy docker://docker.io/library/alpine:latest docker://localhost:5000/alpine:latest
+```
+
+**Copying an image from a running Docker daemon to a directory in the OCI layout**:
+```
+$ mkdir alpine-oci
+$ skopeo copy docker-daemon:alpine:latest oci:alpine-oci
+$ tree alpine-oci
+test-oci/
+├── blobs
+│   └── sha256
+│       ├── 83ef92b73cf4595aa7fe214ec6747228283d585f373d8f6bc08d66bebab531b7
+│       ├── 9a6259e911dcd0a53535a25a9760ad8f2eded3528e0ad5604c4488624795cecc
+│       └── ff8df268d29ccbe81cdf0a173076dcfbbea4bb2b6df1dd26766a73cb7b4ae6f7
+├── index.json
+└── oci-layout
+
+2 directories, 5 files
+```
+
+**Copying an image from a registry to the local storage**:
+```
+$ skopeo copy docker://docker.io/library/alpine:latest containers-storage:alpine:latest
+```
+
+## SEE ALSO
+
+docker-login(1), docker-save(1), ostree(1), podman-login(1), skopeo-copy(1), skopeo-inspect(1), tar(1), container-registries.conf(5), containers-storage.conf(5)
+
+## AUTHORS
+
+Miloslav Trmač <mitr@redhat.com>
+Valentin Rothberg <rothberg@redhat.com>