Merge pull request #122 from justincormack/metadata

Add a "metadata" file contents flag

docs/yaml.md

@@ -96,6 +96,14 @@ Specifying the `mode` is optional, and will default to `0600`. Leading directori
 created if not specified. You can use `~/path` in `source` to specify a path in the build
 user's home directory.
 
+In addition there is a `metadata` option that will generate the file. Currently the only value
+supported here is `"yaml"` which will output the yaml used to generate the image into the specified
+file:
+```
+  - path: etc/linuxkit.yml
+    metadata:yaml
+```
+
 ## `trust`
 
 The `trust` section specifies which build components are to be cryptographically verified with

src/moby/build.go

@@ -3,6 +3,7 @@ package moby
 import (
 	"archive/tar"
 	"bytes"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -359,6 +360,16 @@ func tarAppend(iw *tar.Writer, tr *tar.Reader) error {
 	return nil
 }
 
+// this allows inserting metadata into a file in the image
+func metadata(m Moby, md string) ([]byte, error) {
+	switch md {
+	case "yaml":
+		return json.MarshalIndent(m, "", "    ")
+	default:
+		return []byte{}, fmt.Errorf("Unsupported metadata type: %s", md)
+	}
+}
+
 func filesystem(m Moby, tw *tar.Writer, idMap map[string]uint32) error {
 	// TODO also include the files added in other parts of the build
 	var addedFiles = map[string]bool{}
@@ -410,25 +421,43 @@ func filesystem(m Moby, tw *tar.Writer, idMap map[string]uint32) error {
 		if f.Contents != nil {
 			contents = []byte(*f.Contents)
 		}
-		if !f.Directory && f.Contents == nil && f.Symlink == "" {
-			if f.Source == "" {
-				return errors.New("Contents of file not specified")
+		if !f.Directory && f.Symlink == "" && f.Contents == nil {
+			if f.Source == "" && f.Metadata == "" {
+				return fmt.Errorf("Contents of file (%s) not specified", f.Path)
 			}
-			if len(f.Source) > 2 && f.Source[:2] == "~/" {
-				f.Source = homeDir() + f.Source[1:]
+			if f.Source != "" && f.Metadata != "" {
+				return fmt.Errorf("Specified Source and Metadata for file: %s", f.Path)
 			}
-			if f.Optional {
-				_, err := os.Stat(f.Source)
+			if f.Source != "" {
+				source := f.Source
+				if len(source) > 2 && source[:2] == "~/" {
+					source = homeDir() + source[1:]
+				}
+				if f.Optional {
+					_, err := os.Stat(source)
+					if err != nil {
+						// skip if not found or readable
+						log.Debugf("Skipping file [%s] as not readable and marked optional", source)
+						continue
+					}
+				}
+				var err error
+				contents, err = ioutil.ReadFile(source)
 				if err != nil {
-					// skip if not found or readable
-					log.Debugf("Skipping file [%s] as not readable and marked optional", f.Source)
-					continue
+					return err
+				}
+			} else {
+				contents, err = metadata(m, f.Metadata)
+				if err != nil {
+					return err
 				}
 			}
-			var err error
-			contents, err = ioutil.ReadFile(f.Source)
-			if err != nil {
-				return err
+		} else {
+			if f.Metadata != "" {
+				return fmt.Errorf("Specified Contents and Metadata for file: %s", f.Path)
+			}
+			if f.Source != "" {
+				return fmt.Errorf("Specified Contents and Source for file: %s", f.Path)
 			}
 		}
 		// we need all the leading directories

src/moby/config.go

@@ -29,29 +29,30 @@ type Moby struct {
 
 // KernelConfig is the type of the config for a kernel
 type KernelConfig struct {
-	Image   string
-	Cmdline string
-	Binary  string
-	Tar     *string
+	Image   string  `yaml:"image" json:"image"`
+	Cmdline string  `yaml:"cmdline" json:"cmdline,omitempty"`
+	Binary  string  `yaml:"binary" json:"binary,omitempty"`
+	Tar     *string `yaml:"tar" json:"tar,omitempty"`
 }
 
 // TrustConfig is the type of a content trust config
 type TrustConfig struct {
-	Image []string
-	Org   []string
+	Image []string `yaml:"image" json:"image,omitempty"`
+	Org   []string `yaml:"org" json:"org,omitempty"`
 }
 
 // File is the type of a file specification
 type File struct {
-	Path      string
-	Directory bool
-	Symlink   string
-	Contents  *string
-	Source    string
-	Optional  bool
-	Mode      string
-	UID       interface{} `yaml:"uid" json:"uid"`
-	GID       interface{} `yaml:"gid" json:"gid"`
+	Path      string      `yaml:"path" json:"path"`
+	Directory bool        `yaml:"directory" json:"directory"`
+	Symlink   string      `yaml:"symlink" json:"symlink,omitempty"`
+	Contents  *string     `yaml:"contents" json:"contents,omitempty"`
+	Source    string      `yaml:"source" json:"source,omitempty"`
+	Metadata  string      `yaml:"metadata" json:"metadata,omitempty"`
+	Optional  bool        `yaml:"optional" json:"optional"`
+	Mode      string      `yaml:"mode" json:"mode,omitempty"`
+	UID       interface{} `yaml:"uid" json:"uid,omitempty"`
+	GID       interface{} `yaml:"gid" json:"gid,omitempty"`
 }
 
 // Image is the type of an image config
@@ -65,13 +66,13 @@ type Image struct {
 	Tmpfs             *[]string               `yaml:"tmpfs" json:"tmpfs,omitempty"`
 	Command           *[]string               `yaml:"command" json:"command,omitempty"`
 	Env               *[]string               `yaml:"env" json:"env,omitempty"`
-	Cwd               string                  `yaml:"cwd" json:"cwd"`
-	Net               string                  `yaml:"net" json:"net"`
-	Pid               string                  `yaml:"pid" json:"pid"`
-	Ipc               string                  `yaml:"ipc" json:"ipc"`
-	Uts               string                  `yaml:"uts" json:"uts"`
-	Userns            string                  `yaml:"userns" json:"userns"`
-	Hostname          string                  `yaml:"hostname" json:"hostname"`
+	Cwd               string                  `yaml:"cwd" json:"cwd,omitempty"`
+	Net               string                  `yaml:"net" json:"net,omitempty"`
+	Pid               string                  `yaml:"pid" json:"pid,omitempty"`
+	Ipc               string                  `yaml:"ipc" json:"ipc,omitempty"`
+	Uts               string                  `yaml:"uts" json:"uts,omitempty"`
+	Userns            string                  `yaml:"userns" json:"userns,omitempty"`
+	Hostname          string                  `yaml:"hostname" json:"hostname,omitempty"`
 	Readonly          *bool                   `yaml:"readonly" json:"readonly,omitempty"`
 	MaskedPaths       *[]string               `yaml:"maskedPaths" json:"maskedPaths,omitempty"`
 	ReadonlyPaths     *[]string               `yaml:"readonlyPaths" json:"readonlyPaths,omitempty"`

src/moby/schema.go

@@ -25,6 +25,7 @@ var schema = string(`
           "symlink": {"type": "string"},
           "contents": {"type": "string"},
           "source": {"type": "string"},
+          "metadata": {"type": "string"},
           "optional": {"type": "boolean"},
           "mode": {"type": "string"},
           "uid": {"anyOf": [{"type": "string"}, {"type": "integer"}]},

test/test.yml

@@ -31,6 +31,8 @@ files:
     contents: '{"debug": true}'
   - path: /empty
     contents: ""
+  - path: etc/moby-config
+    metadata: yaml
 trust:
   org:
     - library