feat(unit): Provide units on boot

README.md

@@ -27,6 +27,16 @@ The value of `coreos.etcd.discovery_url` will be used to discover the instance's
 [disco-proto]: https://github.com/coreos/etcd/blob/master/Documentation/discovery-protocol.md
 [disco-service]: http://discovery.etcd.io
 
+#### coreos.units
+
+Arbitrary systemd units may be provided in the `coreos.units` attribute.
+`coreos.units` is a list of objects with the following fields:
+
+- **name**: string representing unit's name
+- **runtime**: boolean indicating whether or not to persist the unit across reboots. This is analagous to the `--runtime` flag to `systemd enable`.
+- **content**: plaintext string representing entire unit file
+
+See docker example below.
 
 ## user-data Script
 
@@ -40,8 +50,7 @@ echo 'Hello, world!'
 
 ## Examples
 
-### Inject an SSH key, bootstrap etcd, and start fleet using a cloud-config
-
+### Inject an SSH key, bootstrap etcd, and start fleet
 ```
 #cloud-config
 
@@ -50,8 +59,29 @@ coreos:
 		discovery_url: https://discovery.etcd.io/827c73219eeb2fa5530027c37bf18877
     fleet:
         autostart: yes
-
 ssh_authorized_keys:
   - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC0g+ZTxC7weoIJLUafOgrm+h...
 ```
 
+### Start a docker container on boot
+
+```
+#cloud-config
+
+coreos:
+    units:
+      - name: docker-redis.service
+        content: |
+          [Unit]
+          Description=Redis container
+          Author=Me
+          After=docker.service
+
+          [Service]
+          Restart=always
+          ExecStart=/usr/bin/docker start -a redis_server
+          ExecStop=/usr/bin/docker stop -t 2 redis_server
+          
+          [Install]
+          WantedBy=local.target
+```

cloudinit/cloud_config.go

@@ -13,6 +13,7 @@ type CloudConfig struct {
 	Coreos              struct {
 		Etcd  struct{ Discovery_URL string }
 		Fleet struct{ Autostart bool }
+		Units []Unit
 	}
 	Write_Files []WriteFile
 }
@@ -60,8 +61,25 @@ func ApplyCloudConfig(cfg CloudConfig, sshKeyName string) error {
 		}
 	}
 
+	if len(cfg.Coreos.Units) > 0 {
+		for _, unit := range cfg.Coreos.Units {
+			dst, err := PlaceUnit("/", &unit)
+			if err != nil {
+				return err
+			}
+			log.Printf("Placed unit %s at %s", unit.Name, dst)
+
+			if err := EnableUnitFile(dst, unit.Runtime); err != nil {
+				return err
+			}
+			log.Printf("Enabled unit %s", unit.Name)
+		}
+		DaemonReload()
+		StartUnits(cfg.Coreos.Units)
+	}
+
 	if cfg.Coreos.Fleet.Autostart {
-		err := StartUnit("fleet.service")
+		err := StartUnitByName("fleet.service")
 		if err == nil {
 			log.Printf("Started fleet service.")
 		} else {

cloudinit/cloud_config_test.go

@@ -37,6 +37,19 @@ coreos:
     discovery_url: "https://discovery.etcd.io/827c73219eeb2fa5530027c37bf18877"
   fleet:
     autostart: Yes
+  units:
+    - name: 50-eth0.network
+      runtime: yes
+      content: '[Match]
+ 
+    Name=eth47
+ 
+ 
+    [Network]
+ 
+    Address=10.209.171.177/19
+ 
+'
 ssh_authorized_keys:
   - foobar
   - foobaz
@@ -90,6 +103,31 @@ write_files:
 			t.Errorf("WriteFile has incorrect owner %s", wf.Owner)
 		}
 	}
+
+	if len(cfg.Coreos.Units) != 1 {
+		t.Error("Failed to parse correct number of units")
+	} else {
+		u := cfg.Coreos.Units[0]
+		expect := `[Match]
+Name=eth47
+
+[Network]
+Address=10.209.171.177/19
+`
+		if u.Content != expect {
+			t.Errorf("Unit has incorrect contents '%s'.\nExpected '%s'.", u.Content, expect)
+		}
+		if u.Runtime != true {
+			t.Errorf("Unit has incorrect runtime value")
+		}
+		if u.Name != "50-eth0.network" {
+			t.Errorf("Unit has incorrect name %s", u.Name)
+		}
+		if u.Type() != "network" {
+			t.Errorf("Unit has incorrect type '%s'", u.Type())
+		}
+	}
+
 }
 
 // Assert that our interface conversion doesn't panic

cloudinit/systemd.go

@@ -2,15 +2,124 @@ package cloudinit
 
 import (
 	"fmt"
+	"io/ioutil"
 	"log"
+	"os"
 	"path"
+	"path/filepath"
+	"strings"
 
 	"github.com/coreos/go-systemd/dbus"
 )
 
+type Unit struct {
+	Name    string
+	Runtime bool
+	Content string
+}
+
+func (u *Unit) Type() string {
+	ext := filepath.Ext(u.Name)
+	return strings.TrimLeft(ext, ".")
+}
+
+func (u *Unit) Group() (group string) {
+	t := u.Type()
+	if t == "network" || t == "netdev" || t == "link" {
+		group = "network"
+	} else {
+		group = "system"
+	}
+	return
+}
+
 type Script []byte
 
-func StartUnit(name string) error {
+func PlaceUnit(root string, u *Unit) (string, error) {
+	dir := "etc"
+	if u.Runtime {
+		dir = "run"
+	}
+
+	dst := path.Join(root, dir, "systemd", u.Group())
+	if _, err := os.Stat(dst); os.IsNotExist(err) {
+		if err := os.MkdirAll(dst, os.FileMode(0755)); err != nil {
+			return "", err
+		}
+	}
+
+	dst = path.Join(dst, u.Name)
+	err := ioutil.WriteFile(dst, []byte(u.Content), os.FileMode(0644))
+	if err != nil {
+		return "", err
+	}
+
+	return dst, nil
+}
+
+func EnableUnitFile(file string, runtime bool) error {
+	conn, err := dbus.New()
+	if err != nil {
+		return err
+	}
+
+	files := []string{file}
+	_, _, err = conn.EnableUnitFiles(files, runtime, true)
+	return err
+}
+
+func separateNetworkUnits(units []Unit) ([]Unit, []Unit) {
+	networkUnits := make([]Unit, 0)
+	nonNetworkUnits := make([]Unit, 0)
+	for _, unit := range units {
+		if unit.Group() == "network" {
+			networkUnits = append(networkUnits, unit)
+		} else {
+			nonNetworkUnits = append(nonNetworkUnits, unit)
+		}
+	}
+	return networkUnits, nonNetworkUnits
+}
+
+func StartUnits(units []Unit) error {
+	networkUnits, nonNetworkUnits := separateNetworkUnits(units)
+	if len(networkUnits) > 0 {
+		if err := RestartUnitByName("systemd-networkd.service"); err != nil {
+			return err
+		}
+	}
+
+	for _, unit := range nonNetworkUnits {
+		if err := RestartUnitByName(unit.Name); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func DaemonReload() error {
+	conn, err := dbus.New()
+	if err != nil {
+		return err
+	}
+
+	_, err = conn.Reload()
+	return err
+}
+
+func RestartUnitByName(name string) error {
+	log.Printf("Restarting unit %s", name)
+	conn, err := dbus.New()
+	if err != nil {
+		return err
+	}
+
+	_, err = conn.RestartUnit(name, "replace")
+	return err
+}
+
+func StartUnitByName(name string) error {
 	conn, err := dbus.New()
 	if err != nil {
 		return err

cloudinit/systemd_test.go

@@ -0,0 +1,102 @@
+package cloudinit
+
+import (
+	"io/ioutil"
+	"os"
+	"path"
+	"syscall"
+	"testing"
+)
+
+func TestPlaceNetworkUnit(t *testing.T) {
+	u := Unit{
+		Name: "50-eth0.network",
+      Runtime: true,
+      Content: `[Match]
+Name=eth47
+
+[Network]
+Address=10.209.171.177/19
+`,
+	}
+
+	dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
+	if err != nil {
+		t.Fatalf("Unable to create tempdir: %v", err)
+	}
+	defer syscall.Rmdir(dir)
+
+	if _, err := PlaceUnit(dir, &u); err != nil {
+		t.Fatalf("PlaceUnit failed: %v", err)
+	}
+
+	fullPath := path.Join(dir, "run", "systemd", "network", "50-eth0.network")
+	fi, err := os.Stat(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to stat file: %v", err)
+	}
+
+	if fi.Mode() != os.FileMode(0644) {
+		t.Errorf("File has incorrect mode: %v", fi.Mode())
+	}
+
+	contents, err := ioutil.ReadFile(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to read expected file: %v", err)
+	}
+
+	expect := `[Match]
+Name=eth47
+
+[Network]
+Address=10.209.171.177/19
+`
+	if string(contents) != expect {
+		t.Fatalf("File has incorrect contents '%s'.\nExpected '%s'", string(contents), expect)
+	}
+}
+
+func TestPlaceMountUnit(t *testing.T) {
+	u := Unit{
+		Name: "media-state.mount",
+      Runtime: false,
+      Content: `[Mount]
+What=/dev/sdb1
+Where=/media/state
+`,
+	}
+
+	dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
+	if err != nil {
+		t.Fatalf("Unable to create tempdir: %v", err)
+	}
+	defer syscall.Rmdir(dir)
+
+	if _, err := PlaceUnit(dir, &u); err != nil {
+		t.Fatalf("PlaceUnit failed: %v", err)
+	}
+
+	fullPath := path.Join(dir, "etc", "systemd", "system", "media-state.mount")
+	fi, err := os.Stat(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to stat file: %v", err)
+	}
+
+	if fi.Mode() != os.FileMode(0644) {
+		t.Errorf("File has incorrect mode: %v", fi.Mode())
+	}
+
+	contents, err := ioutil.ReadFile(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to read expected file: %v", err)
+	}
+
+	expect := `[Mount]
+What=/dev/sdb1
+Where=/media/state
+`
+	if string(contents) != expect {
+		t.Fatalf("File has incorrect contents '%s'.\nExpected '%s'", string(contents), expect)
+	}
+}
+