A Kata Containers initrd image is generated using the initrd_builder.sh script.
This script uses a rootfs directory created by the rootfs-builder/rootfs.sh script.
To create a guest OS initrd image run:
$ sudo ./initrd_builder.sh path/to/rootfs
The rootfs.sh script populates the path/to/rootfs directory.
For more information on how to use the initrd_builder.sh script, run:
$ ./initrd_builder.sh -h