Ubuntu Manpage: containers-transports - description of supported transports for copying and storing

Provided by: golang-github-containers-image_5.23.1-4_all

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.

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 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.

It is further possible to copy data to stdin by specifying docker-archive:/dev/stdin but
note that the used file must be seekable.

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 compliant with the "Open Container Image Layout Specification" at path. Using a
reference is optional and allows for storing multiple images at the same path.

oci-archive:path[:reference]
An image compliant with the "Open Container Image Layout Specification" stored as a tar(1)
archive at path.

ostree:docker-reference[@/absolute/repo/path]
An image in the local ostree(1) repository. /absolute/repo/path defaults to /ostree/repo.

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

AUTHORS

       Miloslav    Trmač    mitr@redhat.com    ⟨mailto:mitr@redhat.com⟩     Valentin     Rothberg
       rothberg@redhat.com ⟨mailto:rothberg@redhat.com⟩

NAME

DESCRIPTION

Examples

SEE ALSO

AUTHORS