etcd.md

cluster store

• it stores all configurations and state of the entire cluster
• etcd is a key value data store used in k8s as default cluster store
• it acts as single source of truth
• when a deployment is done using [[kubectl]], the configuration is stored in cluster store

etcd

• by default etcd listens on port 2379
• it stores data for - minions - nodes - [[pods]] - configs - [[secrets]] - accounts - roles - bindings
• [[kubeadm]] deploys etcd as a pod in kube system namespace

etcdctl

• it is a cli tool for interacting with etcd - --advertise-client-urls parameter is used in etcdctl to make it listen to specific address/port - --intial-cluster is where you specify different instances of etcd service
• it supports two API versions - v2 & v3 - switch between by setting an environment variable - export ETCDCTL_API=3
• when API version is not set, it is assumed to be set to version 2.
• and version 3 commands listed above don't work.
• when API version is set to version 3, version 2 commands listed above don't work.
• path to certificate files must be specified for authentication to etcd
• the certificate files are available in the etcd-master at the following path - - --cacert /etc/kubernetes/pki/etcd/ca.crt
  • --cert /etc/kubernetes/pki/etcd/server.crt
  • --key /etc/kubernetes/pki/etcd/server.key

backups

• when taking backup [[kube api server]] needs to be stopped
• when running backup commands following parameters must be provided
  • --cacert ca certificate
  • --cert etcd server certificate
  • --endpoints endpoints address
  • --key key file

commands

version 2

set key value - create/set a key and value for it get key - get the value of a key backup cluster-health mk mkdir

version 3

get put snapshot save endpoint health

kubectl exec etcd-master -n kube-system -- && \
  sh -c "ETCDCTL_API=3 etcdctl get / --prefix --keys-only --limit=10 && \
  --cacert /etc/kubernetes/pki/etcd/ca.crt --cert && \ /etc/kubernetes/pki/etcd/server.crt  --key &&\ /etc/kubernetes/pki/etcd/server.key" &&