src/cmd/cos_dkms_runner/main.go

package main

import (
	"context"
	"fmt"
	"math/rand"
	"os"
	"cos.googlesource.com/cos/tools.git/src/pkg/containers"

	"github.com/opencontainers/runtime-spec/specs-go"
)

func main() {
	imageName := envOrDefault("IMAGE_NAME", "gcr.io/cos-cloud/cos-dkms:latest")
	containerName := envOrDefault("CONTAINER_NAME", fmt.Sprintf("cos-dkms-%d", rand.Int()))
	containerNamespace := envOrDefault("CONTAINER_NAMESPACE", "cos-dkms")
	containerdSocket := envOrDefault("CONTAINERD_SOCK", "/run/containerd/containerd.sock")

	dirMounts := []specs.Mount{
		{
			Source:      envOrDefault("HOST_DKMS_TREE", "/var/lib/google/dkms/dkms"),
			Destination: envOrDefault("GUEST_DKMS_TREE", "/var/lib/dkms"),
			Options:     []string{"rw", "rbind"},
		},
		{
			Source:      envOrDefault("HOST_SOURCE_TREE", "/var/lib/google/dkms/source"),
			Destination: envOrDefault("GUEST_SOURCE_TREE", "/usr/src"),
			Options:     []string{"rw", "rbind"},
		},
		{
			Source:      envOrDefault("HOST_KERNEL_TREE", "/var/lib/google/dkms/kernel"),
			Destination: envOrDefault("GUEST_KERNEL_TREE", "/lib/modules"),
			Options:     []string{"rw", "rbind"},
		},
		// Mount this so we can use the host's modules as dependencies.
		{
			Source:      envOrDefault("HOST_KERNEL_MODULES_TREE", "/lib/modules"),
			Destination: envOrDefault("GUEST_KERNEL_MODULES_TREE", "/host_modules"),
			Options:     []string{"ro", "rbind"},
		},
	}

	fileMounts := []specs.Mount {
		// Mount this so we can read OS information. There is sensitive information
		// in /etc, so we don't want to mount the full directory.
		{
			Source:      envOrDefault("HOST_LSB_RELEASE_PATH", "/etc/lsb-release"),
			Destination: envOrDefault("GUEST_LSB_RELEASE_PATH", "/etc/lsb-release"),
			Options:     []string{"ro", "bind"},
		},
	}

	args := []string{
		"--gcs-bucket=cos-default",
		"--kernelmodulestree=/host_modules",
		"--logtostderr",
		"--download-workers=0",
	}
	// We prepend the default args first in case a user wants to override them.
	args = append(args, os.Args[1:]...)

	config := containers.ContainerConfig{
		Name:       containerName,
		Command:    "/usr/bin/cos-dkms",
		Args:       args,
		Cwd:        "/",
		DirMounts:  dirMounts,
		FileMounts: fileMounts,
		Privileged: true,
		NetHost:    true,
	}

	ctx := context.Background()
	exitCode, err := containers.Run(ctx, imageName, config, containerNamespace, containerdSocket)

	if exitCode != 0 || err != nil {
		fmt.Errorf("%v\n", err)
		os.Exit(int(exitCode))
	}
}

// envOrDefault returns the value of the environment variable with the given
// name, or a default value if the environment variable is unset.
func envOrDefault(name, defaultValue string) string {
	envValue := os.Getenv(name)
	if envValue == "" {
		return defaultValue
	} else {
		return envValue
	}
}