Disable lxc by default

client/driver/lxc.go

@@ -26,6 +26,9 @@ import (
 )
 
 const (
+	// The option that enables this driver in the Config.Options map.
+	lxcConfigOption = "driver.lxc.enable"
+
 	// containerMonitorIntv is the interval at which the driver checks if the
 	// container is still alive
 	containerMonitorIntv = 2 * time.Second
@@ -143,6 +146,10 @@ func (d *LxcDriver) Validate(config map[string]interface{}) error {
 
 // Fingerprint fingerprints the lxc driver configuration
 func (d *LxcDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
+	enabled := cfg.ReadBoolDefault(lxcConfigOption, false)
+	if !enabled {
+		return false, nil
+	}
 	version := lxc.Version()
 	if version == "" {
 		return false, nil

client/driver/lxc_test.go

@@ -33,8 +33,16 @@ func TestLxcDriver_Fingerprint(t *testing.T) {
 	if err != nil {
 		t.Fatalf("err: %v", err)
 	}
+	if apply {
+		t.Fatalf("should not apply by default")
+	}
+
+	apply, err = d.Fingerprint(&config.Config{Options: map[string]string{lxcConfigOption: "1"}}, node)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 	if !apply {
-		t.Fatalf("should apply")
+		t.Fatalf("should apply with config")
 	}
 	if node.Attributes["driver.lxc"] == "" {
 		t.Fatalf("missing driver")