extract-oci-archive

name	extract-oci-archive
description	Use when you need to extract an OCI archive to inspect its contents, get the rootfs layer, or read the image config.

Extract OCI Archive

Extract the OCI archive structure

mkdir /tmp/oci-extracted
tar -xf /path/to/image.ociarchive -C /tmp/oci-extracted

Get the manifest digest from index.json

MANIFEST=$(jq -r '.manifests[0].digest' /tmp/oci-extracted/index.json \
    | cut -d: -f2)

Extract a layer to get the rootfs

For a single-layer image:

LAYER=$(jq -r '.layers[0].digest' \
    /tmp/oci-extracted/blobs/sha256/${MANIFEST} | cut -d: -f2)
mkdir /tmp/rootfs
tar -xf /tmp/oci-extracted/blobs/sha256/${LAYER} -C /tmp/rootfs

For multi-layer images, extract each layer in order and overlay them.

Read the image config

The config contains the created timestamp, entrypoint, labels, etc.:

CONFIG=$(jq -r '.config.digest' \
    /tmp/oci-extracted/blobs/sha256/${MANIFEST} | cut -d: -f2)
jq . /tmp/oci-extracted/blobs/sha256/${CONFIG}