Anthos on bare metal known issues


1.6.1 version of bmctl cannot install 1.6.0 clusters

Installing a 1.6.0 version of Anthos on bare metal cluster cannot be done via the 1.6.1 version of bmctl. bmctl 1.6.1 can only install the 1.6.1 version of Anthos on bare metal clusters. This issue only applies to admin, hybrid, or standalone clusters installed with bmctl. Clusters installed and managed through admin or hybrid clusters are not affected by this issue.

Control group v2 incompatibility

Control group v2, or cgroup v2 for short, is incompatible with Anthos on bare metal 1.6. Kubernetes 1.18 does not support cgroup v2. Also Docker only offers experimental support as of 20.10. systemd switched to cgroup v2 by default in version 247.2-2. The presence of /sys/fs/cgroup/cgroup.controllers would indicate that your system is using cgroup v2.

Benign error messages during installation

During highly available (HA) cluster installation, you may see errors about etcdserver leader change. These error messages are benign and can be ignored.

When you use bmctl for cluster installation, you may see a Log streamer failed to get BareMetalMachine log message at the very end of the create-cluster.log. This error message is benign and can be ignored.

When examining cluster creation logs, you may notice transient failures about registering clusters or calling webhooks. These errors can be safely ignored, because the installation will retry these operations until they succeed.

Preflight checks and service account credentials

For installations triggered by admin or hybrid clusters (in other words, clusters not created with bmctl, like user clusters), the preflight check does not verify Google Cloud Platform service account credentials or their associated permissions.

Creating cloud monitoring workspace before viewing dashboards

You need to create a cloud monitoring workspace through the Google Cloud Console before you can view any Anthos on bare metal monitoring dashboards,

Application default credentials and bmctl

bmctl uses Application Default Credentials (ADC) to validate the cluster operation's location value in the cluster spec when it is not set to global.

For ADC to work, you need to either point the GOOGLE_APPLICATION_CREDENTIALS environment variable to a service account credential file, or run gcloud auth application-default login.

Docker service

On cluster node machines, if the Docker executable is present in the PATH environment variable, but the Docker service is not active, preflight check will fail and report that the Docker service is not active. To fix this error, either remove Docker, or enable the Docker service.

Upgrading Anthos on bare metal

Upgrading is not available in the 1.6.0 release.


User cluster credentials

The bmctl reset command relies on the top-level credentials section in the cluster configuration file. For user clusters, you will need to manually update the file to add the credentials section.

Mount points and fstab

Reset does not unmount the mount points under /mnt/anthos-system and /mnt/localpv-share/. It also does not clean up the corresponding entries in /etc/fstab.


The cluster CA/certificate will be rotated during upgrade. On-demand rotation support is not currently available.

Anthos on bare metal rotates kubelet serving certificates automatically. Each kubelet node agent can send out a Certificate Signing Request (CSR) when a certificate nears expiration. A controller in your admin clusters validates and approves the CSR.

CSI snapshot webhook does not handle certificate rotation. You need to restart the snapshot webhook pod in order to load the new certificate after the current one expires. As a short-term mitigation of this issue, the expiration period is set to 1 year in the 1.6.0 release.


Bootstrap (kind) cluster IP addresses and cluster node IP addresses overlapping and are the default pod and service CIDRs used by the bootstrap (kind) cluster. Preflight checks will fail if they overlap with cluster node machine IP addresses. To avoid the conflict, you can pass the --bootstrap-cluster-pod-cidr and --bootstrap-cluster-service-cidr flags to bmctl to specify different values.

Overlapping IP addresses across different clusters

There is no preflight check to validate overlapping IP addresses across different clusters.

hostport feature in Anthos on bare metal

The hostport feature in ContainerPort is not currently supported.

Operating system endpoint limitations

On RHEL and CentOS, there is a cluster level limitation of 100,000 endpoints. This number is the sum of all pods that are referenced by a Kubernetes service. If 2 services reference the same set of pods, this counts as 2 separate sets of endpoints. The underlying nftable implementation on RHEL and CentOS causes this limitation; it is not an intrinsic limitation of Anthos on bare metal.


Control plane and node balancer specifications

The control plane and load balancer node pool specifications (control plane spec and node pool spec) are special. These specifications declare and control critical cluster resources. The canonical source for these resources is their respective sections in the

Consequently, do not modify the top-level control plane and load balancer node pool resources directly. Modify the associated sections in the cluster spec instead.

Mutable fields in the cluster and node pool specification

Only the following fields in cluster spec and node pool spec can be updated after the cluster is created (they are mutable fields):

  • For the cluster spec the following fields are mutable:


  • For the node pool spec, the following fields are mutable: