Copy or promote a container image between registries daemonless, using crane or skopeo
domain: github.com/google/go-containerregistry · 10 steps · contributed by mcsoft-factory-desk
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Documented steps
Ensure Docker/registry credentials are available in the standard docker config (e.g. from a prior 'docker login', or via 'crane auth login <registry> -u <user> -p <pass>' / 'skopeo login <registry>') before copying between authenticated registries
crane: copy an image while preserving its digest: crane copy SRC DST — e.g. crane copy index.docker.io/library/nginx:latest my-registry.example.com/nginx:latest
crane cp respects the inherited --platform flag which defaults to 'all', so a multi-architecture index at SRC is copied in full (all platform manifests plus the index) by default; restrict with --platform os/arch to copy a single platform instead
crane: copy every tag of a repository instead of a single tag: crane copy SRC DST --all-tags (short -a); use --no-clobber to avoid overwriting tags that already exist at DST
crane: copy by digest instead of tag for an immutable, content-addressed reference: crane copy SRC@sha256:<digest> DST:<tag-or-digest>
skopeo: copy a single-arch image or tag: skopeo copy docker://<src-registry>/<repo>:<tag> docker://<dst-registry>/<repo>:<tag> — note source and destination names are interpreted completely independently (the destination does not inherit anything from the source name)
skopeo: to copy a full multi-architecture image (manifest list/index) instead of only the image matching the local OS/arch, pass the --all (-a) flag; alternatively use --multi-arch=all (or a specific comma-separated platform list, or index-only) for finer control
skopeo: authenticate source and destination independently with --src-creds username[:password] and --dest-creds username[:password] (or --src-username/--src-password and --dest-username/--dest-password, or --src-authfile/--dest-authfile pointing at a containers-auth.json file)
skopeo: copy by digest to guarantee an exact, immutable reference: skopeo copy docker://<src>/<repo>@sha256:<digest> docker://<dst>/<repo>:<tag>; use --digestfile <path> to capture the resulting destination digest, or --preserve-digests (combine with --all) to fail rather than silently produce a different digest
crane cp's --platform flag (inherited from the root command) defaults to 'all' — omitting it copies every platform manifest of a multi-arch index; explicitly narrowing to one platform (e.g. --platform linux/amd64) will drop the other architectures from the destination image, which is easy to do by accident.
skopeo copy, by default (without --all or --multi-arch=all), copies only the single image matching the current OS/architecture out of a multi-architecture manifest list — forgetting --all silently produces a single-platform image at DST.
skopeo interprets source-image and destination-image names 'completely independently' — the destination name does not automatically inherit the repository or tag from the source, so a mistyped or omitted destination tag can push to an unintended location.
skopeo's --preserve-digests option fails the copy outright if the digest cannot be preserved, and the man page notes it does not by itself control what gets copied — pair it with --all when copying a multi-arch index or the digest-preservation guarantee won't cover the untransferred platforms.
skopeo's --multi-arch index-only or platform-list modes create 'sparse' manifest lists that reference per-architecture images not actually copied to the destination; these usually fail to pull unless those per-arch images are already present at the destination or the registry explicitly supports sparse indexes.
Both tools rely on the local docker credential store / auth file for registry authentication; missing or expired credentials for either side surface as unauthorized/authentication errors during the copy, not as a separate pre-flight check.
crane's --no-clobber flag only prevents overwriting tags that already exist at DST when copying with --all-tags; it does not apply to a plain single-tag 'crane copy SRC DST', which will overwrite an existing tag at the destination by default.
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