add a new method to indicate if the command provides files to snapshot

pkg/commands/add.go

@@ -116,6 +116,10 @@ func (a *AddCommand) FilesToSnapshot() []string {
 	return a.snapshotFiles
 }
 
+func (a *AddCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}
+
 // String returns some information about the command for the image config
 func (a *AddCommand) String() string {
 	return a.cmd.String()

pkg/commands/base_command.go

@@ -32,6 +32,10 @@ func (b *BaseCommand) FilesToSnapshot() []string {
 	return []string{}
 }
 
+func (b *BaseCommand) ProvidesFilesToSnapshot() bool {
+	return false
+}
+
 func (b *BaseCommand) FilesUsedFromContext(_ *v1.Config, _ *dockerfile.BuildArgs) ([]string, error) {
 	return []string{}, nil
 }

pkg/commands/commands.go

@@ -37,6 +37,10 @@ type DockerCommand interface {
 	// A list of files to snapshot, empty for metadata commands or nil if we don't know
 	FilesToSnapshot() []string
 
+	// ProvidesFileToSnapshot is true for all metadata commands and commands which know
+	// list of files changed. False for Run command.
+	ProvidesFilesToSnapshot() bool
+
 	// Return a cache-aware implementation of this command, if it exists.
 	CacheCommand(v1.Image) DockerCommand
 

pkg/commands/copy.go

@@ -138,6 +138,10 @@ func (c *CopyCommand) MetadataOnly() bool {
 	return false
 }
 
+func (c *CopyCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}
+
 func (c *CopyCommand) RequiresUnpackedFS() bool {
 	return true
 }
@@ -210,6 +214,14 @@ func (cr *CachingCopyCommand) FilesToSnapshot() []string {
 	return f
 }
 
+func (cr *CachingCopyCommand) MetadataOnly() bool {
+	return false
+}
+
+func (cr *CachingCopyCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}
+
 func (cr *CachingCopyCommand) String() string {
 	if cr.cmd == nil {
 		return "nil command"

pkg/commands/run.go

@@ -151,6 +151,10 @@ func (r *RunCommand) FilesToSnapshot() []string {
 	return nil
 }
 
+func (r *RunCommand) ProvidesFilesToSnapshot() bool {
+	return false
+}
+
 // CacheCommand returns true since this command should be cached
 func (r *RunCommand) CacheCommand(img v1.Image) DockerCommand {
 
@@ -227,3 +231,11 @@ func (cr *CachingRunCommand) String() string {
 	}
 	return cr.cmd.String()
 }
+
+func (cr *CachingRunCommand) MetadataOnly() bool {
+	return false
+}
+
+func (cr *CachingRunCommand) RequiresUnpackedFS() bool {
+	return true
+}

pkg/commands/workdir.go

@@ -75,3 +75,7 @@ func (w *WorkdirCommand) String() string {
 func (w *WorkdirCommand) MetadataOnly() bool {
 	return false
 }
+
+func (w *WorkdirCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}

pkg/executor/build.go

@@ -347,15 +347,18 @@ func (s *stageBuilder) build() error {
 			default:
 				return false
 			}
-		}
-		if !isCacheCommand() && !initSnapshotTaken {
-			// Take initial snapshot
-			t := timing.Start("Initial FS snapshot")
-			if err := s.snapshotter.Init(); err != nil {
-				return err
+		}()
+		if !initSnapshotTaken && !isCacheCommand && !command.MetadataOnly() {
+			if !command.ProvidesFilesToSnapshot() {
+				// Take initial snapshot if command is not metadata only
+				// and does not return a list of files changed
+				t := timing.Start("Initial FS snapshot")
+				if err := s.snapshotter.Init(); err != nil {
+					return err
+				}
+				timing.DefaultRun.Stop(t)
+				initSnapshotTaken = true
 			}
-			timing.DefaultRun.Stop(t)
-			initSnapshotTaken = true
 		}
 
 		if err := command.ExecuteCommand(&s.cf.Config, s.args); err != nil {
@@ -368,7 +371,7 @@ func (s *stageBuilder) build() error {
 			continue
 		}
 
-		if isCacheCommand() {
+		if isCacheCommand {
 			v := command.(commands.Cached)
 			layer := v.Layer()
 			if err := s.saveLayerToImage(layer, command.String()); err != nil {

pkg/executor/fakes.go

@@ -55,6 +55,9 @@ func (m MockDockerCommand) String() string {
 func (m MockDockerCommand) FilesToSnapshot() []string {
 	return []string{"meow-snapshot-no-cache"}
 }
+func (m MockDockerCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}
 func (m MockDockerCommand) CacheCommand(image v1.Image) commands.DockerCommand {
 	return m.cacheCommand
 }
@@ -84,6 +87,9 @@ func (m MockCachedDockerCommand) String() string {
 func (m MockCachedDockerCommand) FilesToSnapshot() []string {
 	return []string{"meow-snapshot"}
 }
+func (m MockCachedDockerCommand) ProvidesFilesToSnapshot() bool {
+	return true
+}
 func (m MockCachedDockerCommand) CacheCommand(image v1.Image) commands.DockerCommand {
 	return nil
 }

pkg/snapshot/snapshot.go

@@ -39,6 +39,7 @@ var snapshotPathPrefix = config.KanikoDir
 
 // Snapshotter holds the root directory from which to take snapshots, and a list of snapshots taken
 type Snapshotter struct {
+	i         int
 	l         *LayeredMap
 	directory string
 	whitelist []util.WhitelistEntry
@@ -51,7 +52,8 @@ func NewSnapshotter(l *LayeredMap, d string) *Snapshotter {
 
 // Init initializes a new snapshotter
 func (s *Snapshotter) Init() error {
-	logrus.Info("Taking initial snapshot")
+	s.i++
+	logrus.Infof("Taking initial snapshot %d", s.i)
 	_, _, err := s.scanFullFilesystem()
 	return err
 }