skopeo man page

skopeo -- Various operations with container images images and container image registries

Synopsis

skopeo [global options] command [command options]

Description

skopeo is a command line utility providing various operations with container images and container image registries. For example, it is able to inspect a repository on a Docker registry and fetch image. It fetches the repository's manifest and it is able to show you a docker inspect-like json output about a whole repository or a tag. This tool, in contrast to docker inspect, helps you gather useful information about a repository or a tag without requiring you to run docker pull - e.g. - which tags are available for the given repository? which labels the image has?

It also allows you to copy container images between various registries, possibly converting them as necessary, and to sign and verify images.

Image Names

Most commands refer to container images, using a transport:details format. The following formats are supported:

atomic:namespace/stream:tag
An image in the current project of the current default Atomic
Registry. The current project and Atomic Registry instance are by
default read from $HOME/.kube/config, which is set e.g. using
(oc login).

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 $HOME/.docker/config.json,
which is set e.g. using (docker login).

oci:path:tag
An image tag in a directory compliant with "Open Container Image
Layout Specification" at path.

Options

--debug
enable debug output
--username username
for accessing the registry
--password password
for accessing the registry
--cert-path path
Use certificates at path (cert.pem, key.pem) to connect to the registry
--policy path-to-policy
Path to a policy.json file to use for verifying signatures and deciding whether an image is trusted, overriding the default trust policy file.
--registries.d dir
use registry configuration files in dir (e.g. for docker signature storage), overriding the default path.
--tls-verify bool-value
Require HTTPS and verify certificates when talking to docker registries (defaults to true)
--help|-h
Show help
--version|-v
print the version number

skopeo copy

skopeo copy [--sign-by=key-ID] source-image destination-image

Copy an image (manifest, filesystem layers, signatures) from one location to another.

Uses the system's trust policy to validate images, rejects images not trusted by the policy.

source-image use the "image name" format described above

destination-image use the "image name" format described above

--remove-signatures do not copy signatures, if any, from source-image. Necessary when copying a signed image to a destination which does not support signatures.

--sign-by=key-id add a signature using that key ID for an image name corresponding to destination-image

Existing signatures, if any, are preserved as well.

skopeo delete

skopeo delete image-name

Mark image-name for deletion. To release the allocated disk space, you need to execute the docker registry garabage collector. E.g.,

$ docker exec -it registry bin/registry garbage-collect /etc/docker/registry/config.yml

Additionally, the registry must allow deletions by setting REGISTRY_STORAGE_DELETE_ENABLED=true for the registry daemon.

skopeo inspect

skopeo inspect [--raw] image-name

Return low-level information about image-name in a registry

--raw output raw manifest, default is to format in JSON

image-name name of image to retrieve information about

skopeo layers

skopeo layers image-name

Get image layers of image-name

image-name name of the image to retrieve layers

skopeo manifest-digest

skopeo manifest-digest manifest-file

Compute a manifest digest of manifest-file and write it to standard output.

skopeo standalone-sign

skopeo standalone-sign manifest docker-reference key-fingerprint --output|-o signature

This is primarily a debugging tool, or useful for special cases, and usually should not be a part of your normal operational workflow; use skopeo copy --sign-by instead to publish and sign an image in one step.

manifest Path to a file containing the image manifest

docker-reference A docker reference to identify the image with

key-fingerprint Key identity to use for signing

--output|-o output file

skopeo standalone-verify

skopeo standalone-verify manifest docker-reference key-fingerprint signature

Verify a signature using local files, digest will be printed on success.

manifest Path to a file containing the image manifest

docker-reference A docker reference expected to identify the image in the signature

key-fingerprint Expected identity of the signing key

signature Path to signature file

Note: If you do use this, make sure that the image can not be changed at the source location between the times of its verification and use.

skopeo help

show help for skopeo

Files

/etc/containers/policy.json
Default trust policy file, if --policy is not specified.
The policy format is documented in ⟨https://github.com/containers/image/blo…⟩ .

/etc/containers/registries.d
Default directory containing registry configuration, if --registries.d is not specified.
The contents of this directory are documented in ⟨https://github.com/containers/image/blo…⟩ .

skopeo copy

To copy the layers of the docker.io busybox image to a local directory:

$ mkdir -p /var/lib/images/busybox
$ skopeo copy docker://busybox:latest dir:/var/lib/images/busybox
$ ls /var/lib/images/busybox/*
  /tmp/busybox/2b8fd9751c4c0f5dd266fcae00707e67a2545ef34f9a29354585f93dac906749.tar
  /tmp/busybox/manifest.json
  /tmp/busybox/8ddc19f16526912237dd8af81971d5e4dd0587907234be2b83e249518d5b673f.tar

To copy and sign an image:

$ skopeo copy --sign-by dev@example.com atomic:example/busybox:streaming atomic:example/busybox:gold

skopeo delete

Mark image example/pause for deletion from the registry.example.com registry:

$ skopeo delete --force docker://registry.example.com/example/pause:latest

See above for additional details on using the command delete.

skopeo inspect

To review information for the image fedora from the docker.io registry:

$ skopeo inspect docker://docker.io/fedora
{
    "Name": "docker.io/library/fedora",
    "Digest": "sha256:a97914edb6ba15deb5c5acf87bd6bd5b6b0408c96f48a5cbd450b5b04509bb7d",
    "RepoTags": [
        "20",
        "21",
        "22",
        "23",
        "24",
        "heisenbug",
        "latest",
        "rawhide"
    ],
    "Created": "2016-06-20T19:33:43.220526898Z",
    "DockerVersion": "1.10.3",
    "Labels": {},
    "Architecture": "amd64",
    "Os": "linux",
    "Layers": [
        "sha256:7c91a140e7a1025c3bc3aace4c80c0d9933ac4ee24b8630a6b0b5d8b9ce6b9d4"
    ]
}

skopeo layers

Another method to retrieve the layers for the busybox image from the docker.io registry:

$ skopeo layers docker://busybox
$ ls layers-500650331/
  8ddc19f16526912237dd8af81971d5e4dd0587907234be2b83e249518d5b673f.tar
  manifest.json
  a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4.tar

skopeo manifest-digest

$ skopeo manifest-digest manifest.json
sha256:a59906e33509d14c036c8678d687bd4eec81ed7c4b8ce907b888c607f6a1e0e6

skopeo standalone-sign

$ skopeo standalone-sign busybox-manifest.json registry.example.com/example/busybox 1D8230F6CDB6A06716E414C1DB72F2188BB46CC8 --output busybox.signature
$

See skopeo copy above for the preferred method of signing images.

skopeo standalone-verify

$ skopeo standalone-verify busybox-manifest.json registry.example.com/example/busybox 1D8230F6CDB6A06716E414C1DB72F2188BB46CC8  busybox.signature
Signature verified, digest sha256:20bf21ed457b390829cdbeec8795a7bea1626991fda603e0d01b4e7f60427e55

Authors

Antonio Murdaca ⟨runcom@redhat.com⟩, Miloslav Trmac ⟨mitr@redhat.com⟩, Jhon Honce ⟨jhonce@redhat.com⟩

Info

Skopeo Man Pages Jhon Honce August 2016