Prerequisites

UDS Core can run in any CNCF conformant Kubernetes distribution, but sometimes customizations are needed based on environments. This is an attempt to document and link to relevant information to aid in setting up your Kubernetes environment and hosts to ensure a successful UDS Core installation.

Cluster Requirements

When running Kubernetes on any type of host it is important to ensure you are following the upstream documentation from the Kubernetes distribution regarding prerequisites. A few links to upstream documentation are provided below for convenience.

RKE2

K3S

EKS

AKS

UDS Core Requirements

The below are specific requirements for running UDS Core. Some of them are tied to the entire stack of UDS Core and some are more specific to certain components. If you encounter issues with a particular component of core, this can be a good list to check to validate you met all the prerequisite requirements for that specific application.

Default Storage Class

Several UDS Core components require persistent volumes that will be provisioned using the default storage class via dynamic volume provisioning. Ensure that your cluster includes a default storage class prior to deploying. You can validate by running the below command (see example output which includes (default) next to the local-path storage class):

❯ kubectl get storageclass
NAME                   PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
local-path (default)   rancher.io/local-path   Delete          WaitForFirstConsumer   true                   55s

It’s generally beneficial if your storage class supports volume expansion (set allowVolumeExpansion: true, provided your provisioner allows it). This enables you to resize volumes when needed. Additionally, be mindful of any size restrictions imposed by your provisioner. For instance, EBS volumes have a minimum size of 1Gi, which could lead to unexpected behavior, especially during Velero’s CSI backup and restore process. These constraints may also necessitate adjustments to default PVC sizes, such as Keycloak’s PVCs, which default to 512Mi in devMode.

Network Policy Support

The UDS Operator will dynamically provision network policies to secure traffic between components in UDS Core. To ensure these are effective, validate that your CNI supports enforcing network policies. In addition, UDS Core makes use of some CIDR based policies for communication with the KubeAPI server. If you are using Cilium, support for node addressability with CIDR based policies must be enabled with a feature flag.

Istio

Istio requires a number of kernel modules to be loaded for full functionality. The below is a script that will ensure these modules are loaded and persisted across reboots (see also Istio’s upstream requirements list). Ideally this script is used as part of an image build or cloud-init process on each node.

modules=("br_netfilter" "xt_REDIRECT" "xt_owner" "xt_statistic" "iptable_mangle" "iptable_nat" "xt_conntrack" "xt_tcpudp")
for module in "${modules[@]}"; do
  modprobe "$module"
  echo "$module" >> "/etc/modules-load.d/istio-modules.conf"
done

In addition, to run Istio ingress gateways (part of Core) you will need to ensure your cluster supports dynamic load balancer provisioning when services of type LoadBalancer are created. Typically in cloud environments this is handled using a cloud provider’s controller (example: AWS LB Controller). When deploying on-prem, this is commonly done by using a “bare metal” load balancer provisioner like MetalLB or kube-vip. Certain distributions may also include ingress controllers that you will want to disable as they may conflict with Istio (example: RKE2 includes ingress-nginx).

NeuVector

NeuVector historically has functioned best when the host is using cgroup v2. Cgroup v2 is enabled by default on many modern Linux distributions, but you may need to enable it depending on your operating system. Enabling this tends to be OS specific, so you will need to evaluate this for your specific hosts.

Promtail

In order to ensure that Promtail is able to scrape the necessary logs concurrently you may need to adjust some kernel parameters for your hosts. The below is a script that can be used to adjust these parameters to suitable values and ensure they are persisted across reboots. Ideally this script is used as part of an image build or cloud-init process on each node.

declare -A sysctl_settings
sysctl_settings["fs.nr_open"]=13181250
sysctl_settings["fs.inotify.max_user_instances"]=1024
sysctl_settings["fs.inotify.max_user_watches"]=1048576
sysctl_settings["fs.file-max"]=13181250

for key in "${!sysctl_settings[@]}"; do
  value="${sysctl_settings[$key]}"
  sysctl -w "$key=$value"
  echo "$key=$value" > "/etc/sysctl.d/$key.conf"
done
sysctl -p

Metrics Server

Metrics server is provided as an optional component in UDS Core and can be enabled if needed. For distros where metrics-server is already provided, ensure that you do NOT enable metrics-server. See the below as an example for enabling metrics-server if your cluster does not include it.

...
- name: uds-core
  repository: ghcr.io/defenseunicorns/packages/private/uds/core
  ref: 0.25.2-unicorn
  optionalComponents:
    - metrics-server
...

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