# dmverity-vhd

Takes an OCI image locator and an output directory and converts the layers that
make up the image into a series of VHDs in the output directory. One VHD will
be created per image layer.

VHDs are named with the name of the layer SHA.

Each layer contains
[dm-verity](https://www.kernel.org/doc/html/latest/admin-guide/device-mapper/verity.html)
information that can be used to ensure the integrity of the created ext4
filesystem. All VHDs have a layout of:

- ext4 filesystem
- dm-verity superblock
- dm-verity merkle tree
- VHD footer

The output is deterministic except for the UUIDs embedded in the VHD footer and
the dm-verity superblock. Both UUIDs are currently seeded using a random number
generator.

## Example usage

Create VHDs:

```bash
dmverity-vhd create -i alpine:3.12 -o alpine_3_12_layers
```

Compute root hashes:

```bash
dmverity-vhd --docker roothash -i alpine:3.12
```

Compute root hashes with tarball:

```bash
dmverity-vhd --tarball /path/to/tarball.tar roothash -i alpine:3.12
```