Merge pull request #124 from justincormack/onshutdown

Add support for onshutdown

docs/yaml.md

@@ -10,8 +10,8 @@ The yaml configuration specifies the components used to build up an image . All
 are downloaded at build time to create an image. The image is self-contained and immutable,
 so it can be tested reliably for continuous delivery.
 
-The configuration file is processed in the order `kernel`, `init`, `onboot`, `services`, `files`.
-Each section adds file to the root file system. Sections may be omitted.
+The configuration file is processed in the order `kernel`, `init`, `onboot`, `onshutdown`,
+`services`, `files`. Each section adds files to the root file system. Sections may be omitted.
 
 Each container that is specified is allocated a unique `uid` and `gid` that it may use if it
 wishes to run as an isolated user (or user namespace). Anywhere you specify a `uid` or `gid`
@@ -62,6 +62,15 @@ images. They are run sequentially and each must exit before the next one is run.
 These images can be used to configure one shot settings. See [Image
 specification](#image-specification) for a list of supported fields.
 
+## `onshutdown`
+
+This is a list of images to run on a clean shutdown. Note that you must not rely on these
+being run at all, as machines may be be powered off or shut down without having time to run
+these scripts. If you add anything here you should test both in the case where they are
+run and when they are not. Most systems are likely to be "crash only" and not have any setup here,
+but you can attempt to deregister cleanly from a network service here, rather than relying
+on timeouts, for example.
+
 ## `services`
 
 The `services` section is a list of images for long running services which are

src/moby/build.go

@@ -133,6 +133,10 @@ func Build(m Moby, w io.Writer, pull bool, tp string) error {
 		idMap[image.Name] = id
 		id++
 	}
+	for _, image := range m.Onshutdown {
+		idMap[image.Name] = id
+		id++
+	}
 	for _, image := range m.Services {
 		idMap[image.Name] = id
 		id++
@@ -182,6 +186,24 @@ func Build(m Moby, w io.Writer, pull bool, tp string) error {
 		}
 	}
 
+	if len(m.Onshutdown) != 0 {
+		log.Infof("Add onshutdown containers:")
+	}
+	for i, image := range m.Onshutdown {
+		log.Infof("  Create OCI config for %s", image.Image)
+		useTrust := enforceContentTrust(image.Image, &m.Trust)
+		config, err := ConfigToOCI(image, useTrust, idMap)
+		if err != nil {
+			return fmt.Errorf("Failed to create config.json for %s: %v", image.Image, err)
+		}
+		so := fmt.Sprintf("%03d", i)
+		path := "containers/onshutdown/" + so + "-" + image.Name
+		err = ImageBundle(path, image.Image, config, iw, useTrust, pull)
+		if err != nil {
+			return fmt.Errorf("Failed to extract root filesystem for %s: %v", image.Image, err)
+		}
+	}
+
 	if len(m.Services) != 0 {
 		log.Infof("Add service containers:")
 	}

src/moby/config.go

@@ -22,6 +22,7 @@ type Moby struct {
 	Kernel     KernelConfig `kernel:"cmdline" json:"kernel,omitempty"`
 	Init       []string     `init:"cmdline" json:"init"`
 	Onboot     []Image      `yaml:"onboot" json:"onboot"`
+	Onshutdown []Image      `yaml:"onshutdown" json:"onshutdown"`
 	Services   []Image      `yaml:"services" json:"services"`
 	Trust      TrustConfig  `yaml:"trust" json:"trust,omitempty"`
 	Files      []File       `yaml:"files" json:"files"`
@@ -182,6 +183,7 @@ func AppendConfig(m0, m1 Moby) (Moby, error) {
 	}
 	moby.Init = append(moby.Init, m1.Init...)
 	moby.Onboot = append(moby.Onboot, m1.Onboot...)
+	moby.Onshutdown = append(moby.Onshutdown, m1.Onshutdown...)
 	moby.Services = append(moby.Services, m1.Services...)
 	moby.Files = append(moby.Files, m1.Files...)
 	moby.Trust.Image = append(moby.Trust.Image, m1.Trust.Image...)

src/moby/schema.go

@@ -128,6 +128,7 @@ var schema = string(`
     "kernel": { "$ref": "#/definitions/kernel" },
     "init": { "$ref": "#/definitions/strings" },
     "onboot": { "$ref": "#/definitions/images" },
+    "onshutdown": { "$ref": "#/definitions/images" },
     "services": { "$ref": "#/definitions/images" },
     "trust": { "$ref": "#/definitions/trust" },
     "files": { "$ref": "#/definitions/files" }

test/test.yml

@@ -14,6 +14,10 @@ onboot:
   - name: dhcpcd
     image: "linuxkit/dhcpcd:7d2f17a0e5d1ef9a75a527821a9ab0d753b22e7e"
     command: ["/sbin/dhcpcd", "--nobackground", "-f", "/dhcpcd.conf", "-1"]
+onshutdown:
+  - name: shutdown
+    image: busybox:latest
+    command: ["/bin/echo", "so long and thanks for all the fish"]
 services:
   - name: rngd
     image: "linuxkit/rngd:b67c3151a52b05db50e6207b40876900f2208d14"