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Reusing OCI images that contain unikernels🔗

In this page we will explain how we can reuse existing OCI images that contain unikernels to either update or append urunc annotations. As an example, we will use an existing Unikraft Unikernel image from Unikraft's catalog, The goal will be to transform this image to an OCI image that urunc can handle, by simply appending the necessary annotations.

Currently only bunny supports reusing an existing OCI image. However, both file formats, bunnyfile and Dockerfile-like syntax files, can be used.

NOTE: The below steps can be easily adjusted to any existing OCI image.

Using a bunnyfile🔗

In order to append urunc annotations in an existing Unikraft OCI image, we can define the bunnyfile as:

#syntax=harbor.nbfc.io/nubificus/bunny:latest
version: v0.1

platforms:
  framework: unikraft
  monitor: qemu
  architecture: x86

kernel:
  from: unikraft.org/nginx:1.15
  path: /unikraft/bin/kernel

cmdline: "nginx -c /nginx/conf/nginx.conf"

In the above file we specify the followings:

  • We want to use a Unikraft unikernel that will execute on top of Qemu over x86 architecture.
  • We want to use the unikernel binary /unikraft/bin/kernel from the unikraft.org/nginx:1.15 OCI image.
  • We specify the cmdline for the unikernel as nginx -c /nginx/conf/nginx.conf"

With the above file, bunny will fetch the OCI image and append the urunc annotations. We can build the OCI image with the following command:

docker build -f bunnyfile -t urunc/reuse/nginx-unikraft-qemu:test .

Using a Dockerfile-like syntax🔗

In the case of the Dockerfile-like syntax file, we need to manually specify the urunc annotations, using the respective labels. Therefore, to transform the above bunnyfile to the equivalent Containerfile:

#syntax=harbor.nbfc.io/nubificus/bunny:latest
FROM unikraft.org/nginx:1.15

LABEL com.urunc.unikernel.binary="/unikraft/bin/kernel"
LABEL "com.urunc.unikernel.cmdline"="nginx -c /nginx/conf/nginx.conf"
LABEL "com.urunc.unikernel.unikernelType"="unikraft"
LABEL "com.urunc.unikernel.hypervisor"="qemu"

In the above file:

  • We set the unikraft.org/nginx:1.15 as the base for our OCI image.
  • We manually specify through labels the urunc annotations.

We can build the OCI image with the following command:

docker build -f Containerfile -t urunc/prebuilt/nginx-unikraft-qemu:test .