Dynamically lookup the RootDeviceName of the AMI being used

pkg/ami/api.go

@@ -57,6 +57,20 @@ func IsAvailable(api ec2iface.EC2API, id string) (bool, error) {
 	return *output.Images[0].State == "available", nil
 }
 
+// LookupRootDeviceName gets the root block device mapping
+func LookupRootDeviceName(api ec2iface.EC2API, id string) (string, error) {
+	input := &ec2.DescribeImagesInput{
+		ImageIds: []*string{&id},
+	}
+
+	output, err := api.DescribeImages(input)
+	if err != nil {
+		return "", errors.Wrapf(err, "unable to determine root device name for %q", id)
+	}
+
+	return *output.Images[0].RootDeviceName, nil
+}
+
 // FindImage will get the AMI to use for the EKS nodes by querying AWS EC2 API.
 // It will only look for images with a status of available and it will pick the
 // image with the newest creation date.

pkg/apis/eksctl.io/v1alpha5/types.go

@@ -395,6 +395,8 @@ type NodeGroup struct {
 	// +optional
 	VolumeType string `json:"volumeType"`
 	// +optional
+	RootDevice string `json:"rootDevice,omitempty"`
+	// +optional
 	MaxPodsPerNode int `json:"maxPodsPerNode,omitempty"`
 
 	// +optional

pkg/cfn/builder/api_test.go

@@ -248,6 +248,7 @@ var _ = Describe("CloudFormation template builder API", func() {
 		ng.AMIFamily = "AmazonLinux2"
 		ng.VolumeSize = 2
 		ng.VolumeType = api.NodeVolumeTypeIO1
+		ng.RootDevice = "/dev/xvda"
 
 		if withFullVPC {
 			cfg.VPC = testVPC()
@@ -354,6 +355,7 @@ var _ = Describe("CloudFormation template builder API", func() {
 					DesiredCapacity: nil,
 					VolumeSize:      2,
 					VolumeType:      api.NodeVolumeTypeIO1,
+					RootDevice:      "/dev/xvda",
 					IAM: &api.NodeGroupIAM{
 						WithAddonPolicies: api.NodeGroupIAMAddonPolicies{
 							ImageBuilder: api.Disabled(),

pkg/cfn/builder/nodegroup.go

@@ -128,7 +128,7 @@ func (n *NodeGroupResourceSet) addResourcesForNodeGroup() error {
 
 	if n.spec.VolumeSize > 0 {
 		launchTemplateData.BlockDeviceMappings = []gfn.AWSEC2LaunchTemplate_BlockDeviceMapping{{
-			DeviceName: gfn.NewString("/dev/xvda"),
+			DeviceName: gfn.NewString(n.spec.RootDevice),
 			Ebs: &gfn.AWSEC2LaunchTemplate_Ebs{
 				VolumeSize: gfn.NewInteger(n.spec.VolumeSize),
 				VolumeType: gfn.NewString(n.spec.VolumeType),

pkg/ctl/create/cluster.go

@@ -253,6 +253,12 @@ func doCreateCluster(p *api.ProviderConfig, cfg *api.ClusterConfig, nameArg stri
 		}
 		logger.Info("nodegroup %q will use %q [%s/%s]", ng.Name, ng.AMI, ng.AMIFamily, cfg.Metadata.Version)
 
+		// Lookup AMI root device name
+		if err := ctl.GetRootDevice(ng); err != nil {
+			return err
+		}
+		logger.Info("%q has root device %q [%s/%s]", ng.AMI, ng.RootDevice, cfg.Metadata.Version)
+
 		if err := ctl.SetNodeLabels(ng, meta); err != nil {
 			return err
 		}

pkg/ctl/create/nodegroup.go

@@ -121,6 +121,12 @@ func doCreateNodeGroups(p *api.ProviderConfig, cfg *api.ClusterConfig, nameArg s
 		}
 		logger.Info("nodegroup %q will use %q [%s/%s]", ng.Name, ng.AMI, ng.AMIFamily, cfg.Metadata.Version)
 
+		// Lookup AMI root device name
+		if err := ctl.GetRootDevice(ng); err != nil {
+			return err
+		}
+		logger.Info("%q has root device %q [%s/%s]", ng.AMI, ng.RootDevice, cfg.Metadata.Version)
+
 		if err := ctl.SetNodeLabels(ng, meta); err != nil {
 			return err
 		}

pkg/eks/api.go

@@ -260,6 +260,20 @@ func (c *ClusterProvider) EnsureAMI(version string, ng *api.NodeGroup) error {
 	return nil
 }
 
+// GetRootDevice looks up the root device for the ami
+func (c *ClusterProvider) GetRootDevice(ng *api.NodeGroup) (error) {
+
+	// Get Root Device Name
+	rootDevice, err := ami.LookupRootDeviceName(c.Provider.EC2(), ng.AMI)
+	if err != nil {
+		return errors.Wrapf(err, "%s root device name is not available", ng.AMI)
+	}
+
+	ng.RootDevice = rootDevice
+
+	return nil
+}
+
 // SetNodeLabels initialises and validate node labels based on cluster and nodegroup names
 func (c *ClusterProvider) SetNodeLabels(ng *api.NodeGroup, meta *api.ClusterMeta) error {
 	if ng.Labels == nil {