Merge pull request #655 from GijsWeterings/master

Add `--digest-file` flag to output built digest to file.

README.md

@@ -40,6 +40,7 @@ _If you are interested in contributing to kaniko, see [DEVELOPMENT.md](DEVELOPME
     - [--cache-dir](#--cache-dir)
     - [--cache-repo](#--cache-repo)
     - [--cleanup](#--cleanup)
+    - [--digest-file](#--digest-file)
     - [--insecure](#--insecure)
     - [--insecure-pull](#--insecure-pull)
     - [--no-push](#--no-push)
@@ -356,6 +357,18 @@ If `--destination=gcr.io/kaniko-project/test`, then cached layers will be stored
 
 _This flag must be used in conjunction with the `--cache=true` flag._
 
+
+#### --digest-file
+
+Set this flag to specify a file in the container. This file will
+receive the digest of a built image. This can be used to
+automatically track the exact image built by Kaniko.
+
+For example, setting the flag to `--digest-file=/dev/termination-log`
+will write the digest to that file, which is picked up by
+Kubernetes automatically as the `{{.state.terminated.message}}`
+of the container.
+
 #### --insecure-registry
 
 Set this flag to use plain HTTP requests when accessing a registry. It is supposed to be used for testing purposes only and should not be used in production!

cmd/executor/cmd/root.go

@@ -128,6 +128,7 @@ func addKanikoOptionsFlags(cmd *cobra.Command) {
 	RootCmd.PersistentFlags().BoolVarP(&opts.NoPush, "no-push", "", false, "Do not push the image to the registry")
 	RootCmd.PersistentFlags().StringVarP(&opts.CacheRepo, "cache-repo", "", "", "Specify a repository to use as a cache, otherwise one will be inferred from the destination provided")
 	RootCmd.PersistentFlags().StringVarP(&opts.CacheDir, "cache-dir", "", "/cache", "Specify a local directory to use as a cache.")
+	RootCmd.PersistentFlags().StringVarP(&opts.DigestFile, "digest-file", "", "", "Specify a file to save the digest of the built image to.")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Cache, "cache", "", false, "Use cache when building image")
 	RootCmd.PersistentFlags().BoolVarP(&opts.Cleanup, "cleanup", "", false, "Clean the filesystem at the end")
 	RootCmd.PersistentFlags().DurationVarP(&opts.CacheTTL, "cache-ttl", "", time.Hour*336, "Cache timeout in hours. Defaults to two weeks.")

pkg/config/options.go

@@ -30,6 +30,7 @@ type KanikoOptions struct {
 	Target                  string
 	CacheRepo               string
 	CacheDir                string
+	DigestFile              string
 	Destinations            multiArg
 	BuildArgs               multiArg
 	Insecure                bool

pkg/executor/push.go

@@ -19,6 +19,7 @@ package executor
 import (
 	"crypto/tls"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"time"
 
@@ -74,6 +75,19 @@ func CheckPushPermissions(opts *config.KanikoOptions) error {
 // DoPush is responsible for pushing image to the destinations specified in opts
 func DoPush(image v1.Image, opts *config.KanikoOptions) error {
 	t := timing.Start("Total Push Time")
+
+	if opts.DigestFile != "" {
+		digest, err := image.Digest()
+		if err != nil {
+			return errors.Wrap(err, "error fetching digest")
+		}
+		digestByteArray := []byte(digest.String())
+		err = ioutil.WriteFile(opts.DigestFile, digestByteArray, 0644)
+		if err != nil {
+			return errors.Wrap(err, "writing digest to file failed")
+		}
+	}
+
 	destRefs := []name.Tag{}
 	for _, destination := range opts.Destinations {
 		destRef, err := name.NewTag(destination, name.WeakValidation)