| # The Preloader |
| |
| This package is a wrapper around |
| [daisy](https://github.com/GoogleCloudPlatform/compute-daisy). |
| It pulls in config information from the `build.config` file that is generated by the `cos_customizer` |
| which is indirectly populated by the user provided `cloudbuild.yaml` config. |
| The preloader takes this information and generates a daisy config using this template here: |
| |
| `src/data/build_image.wf.json` |
| |
| Once daisy is called and all resources are created, cloud-init will execute the |
| [provisioner](https://cos.googlesource.com/cos/tools/+/refs/heads/master/src/cmd/provisioner) |
| which is the next step of the process. Once cloud-init is done and the provisioner runs to |
| completion, control will be handed back to daisy which will clean up any unecessary resources |
| and exit the build. |
| |
| The provisioner is packaged in an image called `cidata` built in this directory's `BUILD.bazel` |
| file. The image is created, artifacts are copied into the image, and the image is then embedded in |
| `preload.go` where it is then later uploaded to GCS to create a disk to be mounted to the preload |
| VM. |
| |
| A scratch image is also built in the same `BUILD.bazel` file and is used for the `install-gpu` step |
| so that the toolchain isn't installed onto the boot disk and is instead bindmounted and executed |
| from temporary storage. Much like cidata, the scratch image is also embedded in the `preload.go` |
| file and uploaded to GCS to allow daisy to create a temporary ext4 disk for gpu installation. |
