rkt: allow specifying --group

CHANGELOG.md

@@ -33,6 +33,7 @@ IMPROVEMENTS:
  * driver/docker: Support adding or dropping capabilities [[GH-3754](https://github.com/hashicorp/nomad/issues/3754)]
  * driver/docker: Support mounting root filesystem as read-only [[GH-3802](https://github.com/hashicorp/nomad/issues/3802)]
  * driver/lxc: Add volumes config to LXC driver [[GH-3687](https://github.com/hashicorp/nomad/issues/3687)]
+ * driver/rkt: Allow overriding group [[GH-3990](https://github.com/hashicorp/nomad/issues/3990)]
  * telemetry: Support DataDog tags [[GH-3839](https://github.com/hashicorp/nomad/issues/3839)]
 
 BUG FIXES:

client/driver/rkt.go

@@ -88,8 +88,9 @@ type RktDriverConfig struct {
 	Volumes          []string            `mapstructure:"volumes"`            // Host-Volumes to mount in, syntax: /path/to/host/directory:/destination/path/in/container[:readOnly]
 	InsecureOptions  []string            `mapstructure:"insecure_options"`   // list of args for --insecure-options
 
-	NoOverlay bool `mapstructure:"no_overlay"` // disable overlayfs for rkt run
-	Debug     bool `mapstructure:"debug"`      // Enable debug option for rkt command
+	NoOverlay bool   `mapstructure:"no_overlay"` // disable overlayfs for rkt run
+	Debug     bool   `mapstructure:"debug"`      // Enable debug option for rkt command
+	Group     string `mapstructure:"group"`      // Group override for the container
 }
 
 // rktHandle is returned from Start/Open as a handle to the PID
@@ -294,6 +295,9 @@ func (d *RktDriver) Validate(config map[string]interface{}) error {
 			"insecure_options": {
 				Type: fields.TypeArray,
 			},
+			"group": {
+				Type: fields.TypeString,
+			},
 		},
 	}
 
@@ -577,6 +581,12 @@ func (d *RktDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse,
 		prepareArgs = append(prepareArgs, fmt.Sprintf("--user=%s", task.User))
 	}
 
+	// There's no task-level parameter for groups so check the driver
+	// config for a custom group
+	if driverConfig.Group != "" {
+		prepareArgs = append(prepareArgs, fmt.Sprintf("--group=%s", driverConfig.Group))
+	}
+
 	// Add user passed arguments.
 	if len(driverConfig.Args) != 0 {
 		parsed := ctx.TaskEnv.ParseAndReplace(driverConfig.Args)

client/driver/rkt_test.go

@@ -344,25 +344,25 @@ func TestRktDriver_Start_Wait_AllocDir(t *testing.T) {
 	}
 }
 
-func TestRktDriverUser(t *testing.T) {
-	assert := assert.New(t)
+// TestRktDriver_UserGroup asserts tasks may override the user and group of the
+// rkt image.
+func TestRktDriver_UserGroup(t *testing.T) {
 	if !testutil.IsTravis() {
 		t.Parallel()
 	}
 	if os.Getenv("NOMAD_TEST_RKT") == "" {
 		t.Skip("skipping rkt tests")
 	}
-
 	ctestutils.RktCompatible(t)
+	require := assert.New(t)
+
 	task := &structs.Task{
 		Name:   "etcd",
 		Driver: "rkt",
-		User:   "alice",
+		User:   "nobody",
 		Config: map[string]interface{}{
-			"trust_prefix": "coreos.com/etcd",
-			"image":        "coreos.com/etcd:v2.0.4",
-			"command":      "/etcd",
-			"args":         []string{"--version"},
+			"image": "docker://redis:3.2",
+			"group": "nogroup",
 		},
 		LogConfig: &structs.LogConfig{
 			MaxFiles:      10,
@@ -374,23 +374,37 @@ func TestRktDriverUser(t *testing.T) {
 		},
 	}
 
-	ctx := testDriverContexts(t, task)
-	defer ctx.AllocDir.Destroy()
-	d := NewRktDriver(ctx.DriverCtx)
+	tctx := testDriverContexts(t, task)
+	defer tctx.AllocDir.Destroy()
+	d := NewRktDriver(tctx.DriverCtx)
 
-	_, err := d.Prestart(ctx.ExecCtx, task)
-	assert.Nil(err)
-	resp, err := d.Start(ctx.ExecCtx, task)
-	assert.Nil(err)
+	_, err := d.Prestart(tctx.ExecCtx, task)
+	require.Nil(err)
+	resp, err := d.Start(tctx.ExecCtx, task)
+	require.Nil(err)
 	defer resp.Handle.Kill()
 
-	select {
-	case res := <-resp.Handle.WaitCh():
-		assert.False(res.Successful())
-	case <-time.After(time.Duration(testutil.TestMultiplier()*15) * time.Second):
-		t.Fatalf("timeout")
-	}
+	timeout := time.Duration(testutil.TestMultiplier()*15) * time.Second
+
+	ctx, cancel := context.WithTimeout(context.Background(), timeout)
+	defer cancel()
 
+	// WaitUntil we can determine the user/group redis is running as
+	expected := []byte("redis-server *:6379         nobody   nogroup\n")
+	testutil.WaitForResult(func() (bool, error) {
+		raw, code, err := resp.Handle.Exec(ctx, "/bin/bash", []string{"-c", "ps -eo args,user,group | grep ^redis"})
+		if err != nil {
+			return false, err
+		}
+		if code != 0 {
+			return false, fmt.Errorf("unexpected exit code: %d", code)
+		}
+		return bytes.Equal(expected, raw), fmt.Errorf("expected %q but found %q", expected, raw)
+	}, func(err error) {
+		t.Fatalf("err: %v", err)
+	})
+
+	require.Nil(resp.Handle.Kill())
 }
 
 func TestRktTrustPrefix(t *testing.T) {
@@ -476,7 +490,7 @@ func TestRktDriver_PortsMapping(t *testing.T) {
 		Name:   "etcd",
 		Driver: "rkt",
 		Config: map[string]interface{}{
-			"image": "docker://redis:latest",
+			"image": "docker://redis:3.2",
 			"port_map": []map[string]string{
 				{
 					"main": "6379-tcp",