Initial commit: OCI image mounting via containers-storage

slocker-lite validates an OCI Image Layout tar, imports its layers into containers-storage's layer store in order, and mounts the assembled image using fuse-overlayfs, printing the resulting merged path. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-08-10 08:12:50 +00:00
commit a301dfb44f
16 changed files with 1141 additions and 0 deletions
@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+"""Writes a minimal one-layer OCI Image Layout tar to the path given as argv[1].
+
+Used by meson.build to produce a fixture for the `meson test` smoke test.
+"""
+
+import gzip
+import hashlib
+import io
+import json
+import sys
+import tarfile
+
+
+def sha256_hex(data: bytes) -> str:
+    return hashlib.sha256(data).hexdigest()
+
+
+def add_bytes(tar: tarfile.TarFile, name: str, data: bytes) -> None:
+    info = tarfile.TarInfo(name=name)
+    info.size = len(data)
+    tar.addfile(info, io.BytesIO(data))
+
+
+def main() -> None:
+    out_path = sys.argv[1]
+
+    # Uncompressed layer content: a tiny tar with a single file.
+    layer_tar_buf = io.BytesIO()
+    with tarfile.open(fileobj=layer_tar_buf, mode="w") as layer_tar:
+        add_bytes(layer_tar, "hello.txt", b"hello from slocker-lite fixture\n")
+    layer_tar_bytes = layer_tar_buf.getvalue()
+    diff_id = sha256_hex(layer_tar_bytes)
+
+    layer_gz_bytes = gzip.compress(layer_tar_bytes)
+    layer_digest = sha256_hex(layer_gz_bytes)
+
+    config = {
+        "architecture": "amd64",
+        "os": "linux",
+        "config": {},
+        "rootfs": {"type": "layers", "diff_ids": [f"sha256:{diff_id}"]},
+    }
+    config_bytes = json.dumps(config).encode()
+    config_digest = sha256_hex(config_bytes)
+
+    manifest = {
+        "schemaVersion": 2,
+        "mediaType": "application/vnd.oci.image.manifest.v1+json",
+        "config": {
+            "mediaType": "application/vnd.oci.image.config.v1+json",
+            "digest": f"sha256:{config_digest}",
+            "size": len(config_bytes),
+        },
+        "layers": [
+            {
+                "mediaType": "application/vnd.oci.image.layer.v1.tar+gzip",
+                "digest": f"sha256:{layer_digest}",
+                "size": len(layer_gz_bytes),
+            }
+        ],
+    }
+    manifest_bytes = json.dumps(manifest).encode()
+    manifest_digest = sha256_hex(manifest_bytes)
+
+    index = {
+        "schemaVersion": 2,
+        "manifests": [
+            {
+                "mediaType": "application/vnd.oci.image.manifest.v1+json",
+                "digest": f"sha256:{manifest_digest}",
+                "size": len(manifest_bytes),
+            }
+        ],
+    }
+    index_bytes = json.dumps(index).encode()
+
+    oci_layout_bytes = json.dumps({"imageLayoutVersion": "1.0.0"}).encode()
+
+    with tarfile.open(out_path, mode="w") as tar:
+        add_bytes(tar, "oci-layout", oci_layout_bytes)
+        add_bytes(tar, "index.json", index_bytes)
+        add_bytes(tar, f"blobs/sha256/{config_digest}", config_bytes)
+        add_bytes(tar, f"blobs/sha256/{manifest_digest}", manifest_bytes)
+        add_bytes(tar, f"blobs/sha256/{layer_digest}", layer_gz_bytes)
+
+
+if __name__ == "__main__":
+    main()