Kubernetes is a Platform-as-a-Service (PAAS) build on top of (docker) containers, but with an additional unit of abstraction called a pod, which a) is its smallest unit of execution b) has a single external IP address, c) is a group of one or more containers where d) the group of containers are connected over a network namespace and e) each pod is isolated from others by network namespaces. Within a pod, different containers can see each other over different ports over a loopback interface. Within an instance, while different pods can see each other as different IP addresses. It has a control plane built on top of etcd, a consistent, distributed, highly available key-value store, which is an independent opensource CNCF project.
It is conceptually similar to Cloud Foundry, Mesos, OpenStack, Mirantis and similar abstraction layers.
A threat matrix for Kubernetes by MS – https://www.microsoft.com/security/blog/2020/04/02/attack-matrix-kubernetes/
From RSA’20, here’s a talk on ‘The future of Kubernetes attacks’ – https://youtu.be/CH7S5rE3j8w
From Coinbase, a blog on ‘Why Kubernetes is not part of our stack’ – https://blog.coinbase.com/container-technologies-at-coinbase-d4ae118dcb6c makes these points
- it needs a full-time compute team to maintain
- securing it is neither trivial nor well understood. SPIFFE, SPIRE, Envoy, Istio, OPA, service mesh are a few of the technologies.
This blog links to – https://k8s.af/
Another viewpoint – https://pythonspeed.com/articles/dont-need-kubernetes/
A counterpoint to the Coinbase blog – https://blog.kumina.nl/2020/07/in-response-to-container-technologies-at-coinbase/
K8S is based on a Controller pattern:
- Resources capture the desired state
- Current state is kept centralized in etcd, a distributed key-value store, similar to Consul
- Controllers reconcile current state with desired state
Pod is a top level resource, is the smallest deployment unit, and is a group of one or more containers described by a yaml file, similar to docker-compose.yml .
K8S Operator is a kind of resource manager, for Custom resources.
Spinnaker is a Continuous Delivery platform that itself runs on k8s as a set of pods which can be scaled up
A kubectl cheat sheet:
An article on cloud security https://medium.com/xm-cyber/having-fun-with-cloud-services-e281f8a7fe60 , which I think makes the point of why things are relatively complex to begin with.
One comes across the terms helm and helm charts. Helm is a way to package a complex k8s application. This adds a layer of indirection to an app – https://stepan.wtf/to-helm-or-not/ .
A repo to list failing pods – https://github.com/edrevo/suspicious-pods
Exploring networking in k8s – https://dustinspecker.com/posts/how-do-kubernetes-and-docker-create-ip-addresses/
Plugin for Pod networking on EKS using ENIs – https://github.com/aws/amazon-vpc-cni-k8s
Hardening EKS with IAM, RBAC – https://snyk.io/blog/hardening-aws-eks-security-rbac-secure-imds-audit-logging/
EKS Authentication with IAM – how does it work ?
IAM is only used for authentication of valid IAM entities. All permissions for interacting with EKS Kubernetes API is managed through the native Kubernetes RBAC system.
AWS IAM Authenticator for EKS is a component that enables access to EKS via IAM, for provisioning, managing, updating the cluster. It runs on the EKS Control Plane – https://github.com/kubernetes-sigs/aws-iam-authenticator#aws-iam-authenticator-for-kubernetes
A k8s ConfigMap is used to store non-confidential data in key-value pairs.
The above authenticator gets its configuration information from the
ConfigMap. This ConfigMap can be edited via eksctl (recommended) or be directly edited.
A Kubernetes service account provides an identity for processes that run in a pod. For more information see Managing Service Accounts in the Kubernetes documentation. If your pod needs access to AWS services, you can map the service account to an AWS Identity and Access Management identity to grant that access.
EKS Networking – https://aws.amazon.com/blogs/containers/de-mystifying-cluster-networking-for-amazon-eks-worker-nodes/