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* [kubectl - BASH autocompletion](#kubectl-bash-autocompletion)
* [Install k3s](#install-k3s)
* [On on-premises](#install-k3s-on-premises)
* [Configure upstream DNS-resolver](#upstream-dns-resolver)
* [Change NodePort range](#nodeport-range)
* [Clustering](#clustering)
* [On Docker with k3d](#install-k3s-on-docker-k3d)
* [Namespaces and resource limits](#namespaces-limits)
* [Persistent volumes (StorageClass - dynamic provisioning)](#pv)
* [Rancher Local](#pv-local)
* [Rancher Longhorn - distributed in local cluster](#pv-longhorn)
* [NFS](#pv-nfs)
* [Seaweedfs](#pv-seaweedfs)
* [Ingress controller](#ingress-controller)
* [Disable Traefik-ingress](#disable-traefik-ingress)
* [Enable NGINX-ingress with OCSP stapling](#enable-nginx-ingress)
* [Installation](#install-nginx-ingress)
* [Cert-Manager (references ingress controller)](#cert-manager)
* [Installation](#cert-manager-install)
* [Cluster-internal CA issuer](#cert-manager-cluster-ca-issuer)
* [Let´s Encrypt issuer](#cert-manager-le-issuer)
* [Deploying a LE-certificate with ingress](#cert-manager-ingress)
* [Deploying a LE-certificate by CRD](#cert-manager-crd)
* [Troubleshooting](#cert-manager-troubleshooting)
* [HELM charts](#helm)
* [Create a chart](#helm-create)
* [Install local chart without packaging](#helm-install-without-packaging)
* [List deployed helm charts](#helm-list)
* [Upgrade local chart without packaging](#helm-upgrade)
* [Get status of deployed chart](#helm-status)
* [Get deployment history](#helm-history)
* [Rollback](#helm-rollback)
* [Kubernetes in action](#kubernetes-in-action)
* [Running DaemonSets on `hostPort`](#running-daemonsets)
* [Running StatefulSet with NFS storage](#running-statefulset-nfs)
* [Services](#services)
* [Client-IP transparency and loadbalancing](#services-client-ip-transparency)
* [Session affinity/persistence](#services-session-persistence)
* [Keep your cluster balanced](#keep-cluster-balanced)
* [Node maintenance](#node-maintenance)
* [What happens if a node goes down?](#what-happens-node-down)
* [Dealing with disruptions](#disruptions)
* [Troubleshooting](#troubleshooting)
* [Deleting a stuck namespace](#ts-delete-stuck-namespace)
* [Deleting stuck CRDs](#ts-delete-stuck-crd)
# kubectl - BASH autocompletion <a name="user-content-kubectl-bash-autocompletion"></a>
For current shell only:
```
source <(kubectl completion bash)
```
Persistent:
```
echo "source <(kubectl completion bash)" >> ~/.bashrc
```
# Install k3s <a name="user-content-install-k3s"></a>
## On premises <a name="user-content-install-k3s-on-premises"></a>
https://k3s.io/:
```
curl -sfL https://get.k3s.io | sh -
```
If disired, set a memory consumption limit of the systemd-unit like so:
```
root#> mkdir /etc/systemd/system/k3s.service.d
root#> vi /etc/systemd/system/k3s.service.d/limits.conf
[Service]
MemoryMax=1024M
root#> systemctl daemon-reload
root#> systemctl restart k3s
root#> systemctl status k3s
k3s.service - Lightweight Kubernetes
Loaded: loaded (/etc/systemd/system/k3s.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/k3s.service.d
└─limits.conf
Active: active (running) since Thu 2020-11-26 10:46:26 CET; 13min ago
Docs: https://k3s.io
Process: 9618 ExecStartPre=/sbin/modprobe br_netfilter (code=exited, status=0/SUCCESS)
Process: 9619 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS)
Main PID: 9620 (k3s-server)
Tasks: 229
Memory: 510.6M (max: 1.0G)
CGroup: /system.slice/k3s.service
```
### Upstream DNS-resolver <a name="user-content-upstream-dns-resolver"></a>
Docs: https://rancher.com/docs/rancher/v2.x/en/troubleshooting/dns/
Default: 8.8.8.8 => does not resolve local domains!
1. local /etc/resolv.k3s.conf -> ip-of-dnsresolver (127.0.0.1 **does not work!**)
2. vi /etc/systemd/system/k3s.service:
```
[...]
ExecStart=/usr/local/bin/k3s \
server [...] --resolv-conf /etc/resolv.k3s.conf \
```
3. Re-load systemd config: `systemctl daemon-reload`
4. Re-start k3s: `systemctl restart k3s.service`
5. Re-deploy coredns-pods: `kubectl -n kube-system delete pod name-of-coredns-pods`
### Change NodePort range to 1 - 65535 <a name="user-content-nodeport-range"></a>
1. vi /etc/systemd/system/k3s.service:
```
[...]
ExecStart=/usr/local/bin/k3s \
server [...] --kube-apiserver-arg service-node-port-range=1-65535 \
```
2. Re-load systemd config: `systemctl daemon-reload`
3. Re-start k3s: `systemctl restart k3s.service`
### Clustering <a name="user-content-clustering"></a>
If you want to build a K3s-cluster the default networking model is *overlay@VXLAN*. In this case make sure that
* all of your nodes can reach (ping) each other over the underlying network (local, routed/vpn). This is required for the overlay network to work properly. VXLAN spans a mashed network over all K3s-nodes.
* if your nodes are spread over public networks (like the internet) use a VPN (like IPSec or OpenVPN) to secure the traffic between the nodes. **VXLAN uses plain UDP for transport!**
* if your nodes are connected through VPN, `flannel` (overlay network daemon) should explicitly communicate over the vpn network interface instead of the public network interface. Following settings should be made on the nodes:
```
/etc/systemd/system/k3s-agent.service:
[...]
ExecStartPre=sleep 60
ExecStart=/usr/local/bin/k3s \
agent \
--flannel-iface <name-of-vpn-interface> \
```
## On Docker with K3d <a name="user-content-install-k3s-on-docker-k3d"></a>
K3d is a terraforming orchestrator which deploys a K3s cluster (masters and nodes) directly on docker without the need for virtual machines for each node (master/worker).
* Prerequisites: a local docker installation **without user-namespaces enabled**.
* **Warning**: K3d deploys privileged containers!
https://k3d.io/:
```
curl -s https://raw.githubusercontent.com/rancher/k3d/main/install.sh | bash
```
Create a K3s cluster without `traefik` as well as `metrics-server`
```
k3d cluster create cluster1 \
--agents 2 \
--k3s-server-arg '--disable=traefik' \
--k3s-server-arg '--disable=metrics-server' \
--k3s-server-arg '--kube-apiserver-arg=service-node-port-range=1-65535'
```
If you encounter `helm` throwing errors like this one:
```
Error: Kubernetes cluster unreachable
```
... just do:
```
$ kubectl config view --raw > ~/kubeconfig-k3d.yaml
$ export KUBECONFIG=~/kubeconfig-k3d.yaml
```
If you need to change the upstream DNS-resolver:
```
kubectl -n kube-system edit configmap coredns
```
Find the line containing
```
forward . /etc/resolv.conf
```
and change the content to
```
forward . ipaddr.of.your.dns-resolver
```
Finally redeploy the CoreDNS deployment with:
`kubectl -n kube-system rollout restart deployment coredns`
**Note:** If you restart the cluster (`k3d cluster stop your-cluster` and `k3d cluster start your-cluster`), the changes will be gone!
# Namespaces and resource limits <a name="user-content-namespaces-limits"></a>
```
kubectl apply -f https://gitea.zwackl.de/dominik/k3s/raw/branch/master/namespaces_limits.yaml
```
# Persistent Volumes (StorageClass - dynamic provisioning) <a name="user-content-pv"></a>
Read more about [AccessModes](https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes)
## Rancher Local <a name="user-content-pv-local"></a>
https://rancher.com/docs/k3s/latest/en/storage/
Only supports *AccessMode*: ReadWriteOnce (RWO)
## Longhorn (distributed in local cluster) <a name="user-content-pv-longhorn"></a>
* Requirements: https://longhorn.io/docs/0.8.0/install/requirements/
* Debian: `apt install open-iscsi`
* Install: https://rancher.com/docs/k3s/latest/en/storage/
## NFS <a name="user-content-pv-nfs"></a>
For testing purposes as well as simplicity you may use following [NFS container image](https://hub.docker.com/r/itsthenetwork/nfs-server-alpine):
```
mkdir -p
docker run -d --name nfs-server \
--net=host \
--privileged \
-v /data/docker/nfs-server/data/:/nfsshare \
-e SHARED_DIRECTORY=/nfsshare \
itsthenetwork/nfs-server-alpine:latest
```
**All Nodes need to have the NFS-client package (Ubuntu: `nfs-common`) installed**
```
helm repo add ckotzbauer https://ckotzbauer.github.io/helm-charts
helm install my-nfs-client-provisioner --set nfs.server=<nfs-server/ip-addr> --set nfs.path=</data/nfs> ckotzbauer/nfs-client-provisioner
```
Check if NFS *StorageClass* is available:
```
$ kubectl get sc
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
local-path (default) rancher.io/local-path Delete WaitForFirstConsumer false 101d
nfs-client cluster.local/my-nfs-client-provisioner Delete Immediate true 172m
```
Now you can use `nfs-client` as StorageClass like so:
```
apiVersion: apps/v1
kind: StatefulSet
[...]
volumeClaimTemplates:
- metadata:
name: nfs-backend
spec:
accessModes: [ "ReadWriteMany" ]
storageClassName: "nfs-client"
resources:
requests:
storage: 32Mi
```
or so:
```
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: nfs-pvc-1
namespace: <blubb>
spec:
storageClassName: "nfs-client"
accessModes:
- ReadWriteMany
resources:
requests:
storage: 32Mi
```
## Seaweedfs <a name="user-content-pv-seaweedfs"></a>
Docs: https://github.com/seaweedfs
Docs: https://github.com/seaweedfs/seaweedfs-csi-driver
In order to use the CSI driver you need to have a working seaweedfs-cluster. As seaweedfs is really lightweight it can be deployed on a bunch (at least three) of raspberries (min. version 3) as well as on the K3s cluster too.
# Ingress controller <a name="user-content-ingress-controller"></a>
## Disable Traefik-ingress <a name="user-content-disable-traefik-ingress"></a>
edit /etc/systemd/system/k3s.service:
```
[...]
ExecStart=/usr/local/bin/k3s \
server --disable traefik --resolv-conf /etc/resolv.conf \
[...]
```
Finally `systemctl daemon-reload` and `systemctl restart k3s`
## Enable K8s own NGINX-ingress with OCSP stapling <a name="user-content-enable-nginx-ingress"></a>
### Installation <a name="user-content-install-nginx-ingress"></a>
This is the helm chart of the K8s own nginx ingress controller:
https://kubernetes.github.io/ingress-nginx/deploy/#using-helm
```
kubectl create ns ingress-nginx
helm repo add ingress-nginx https://kubernetes.github.io/ingress-nginx
helm install my-release ingress-nginx/ingress-nginx -n ingress-nginx
```
`kubectl -n ingress-nginx get all`:
```
NAME READY STATUS RESTARTS AGE
pod/svclb-my-release-ingress-nginx-controller-m6gxl 2/2 Running 0 110s
pod/my-release-ingress-nginx-controller-695774d99c-t794f 1/1 Running 0 110s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/my-release-ingress-nginx-controller-admission ClusterIP 10.43.116.191 <none> 443/TCP 110s
service/my-release-ingress-nginx-controller LoadBalancer 10.43.55.41 192.168.178.116 80:31110/TCP,443:31476/TCP 110s
NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE
daemonset.apps/svclb-my-release-ingress-nginx-controller 1 1 1 1 1 <none> 110s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/my-release-ingress-nginx-controller 1/1 1 1 110s
NAME DESIRED CURRENT READY AGE
replicaset.apps/my-release-ingress-nginx-controller-695774d99c 1 1 1 110s
```
As nginx ingress is hungry for memory, let´s reduce the number of workers to 1:
```
kubectl -n ingress-nginx edit configmap my-release-ingress-nginx-controller
apiVersion: v1
<<<ADD BEGINN>>>
data:
enable-ocsp: "true"
worker-processes: "1"
<<<ADD END>>>
kind: ConfigMap
[...]
```
Finally the deployment needs to be restarted:
`kubectl -n ingress-nginx rollout restart deployment my-release-ingress-nginx-controller`
**If you are facing deployment problems like the following one**
```
Error: UPGRADE FAILED: cannot patch "gitea-ingress-staging" with kind Ingress: Internal error occurred: failed calling webhook "validate.nginx.ingress.kubernetes.io": Post https://my-release-ingress-nginx-controller-admission.ingress-nginx.svc:443/networking/v1beta1/ingresses?timeout=10s: context deadline exceeded
```
A possible fix: `kubectl -n ingress-nginx delete ValidatingWebhookConfiguration my-release-ingress-nginx-admission`
# Cert-Manager (references ingress controller) <a name="user-content-cert-manager"></a>
## Installation <a name="user-content-cert-manager-install"></a>
Docs: https://hub.helm.sh/charts/jetstack/cert-manager
**Note on split-horizon DNS**: If you are planning to use DNS-01 validation in term of [split-horizon-DNS](https://en.wikipedia.org/wiki/Split-horizon_DNS), you will need to specify an external DNS-resolver (Google, Cloudflare or your ISPs resolver) instead of your internal upstream DNS-resolver for DNS self-checks! Read [this](https://cert-manager.io/docs/configuration/acme/dns01/#setting-nameservers-for-dns01-self-check) for further details.
```
helm repo add jetstack https://charts.jetstack.io
helm repo update
kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/download/v1.0.2/cert-manager.crds.yaml
kubectl create namespace cert-manager
helm install cert-manager --namespace cert-manager --set 'extraArgs={--dns01-recursive-nameservers-only,--dns01-recursive-nameservers=8.8.8.8:53\,1.1.1.1:53}' jetstack/cert-manager
kubectl -n cert-manager get all
```
## Cluster-internal CA Issuer <a name="user-content-cert-manager-cluster-ca-issuer"></a>
Docs: https://cert-manager.io/docs/configuration/ca/
## Let´s Encrypt issuer <a name="user-content-cert-manager-le-issuer"></a>
Docs: https://cert-manager.io/docs/tutorials/acme/ingress/#step-6-configure-let-s-encrypt-issuer
```
ClusterIssuers are a resource type similar to Issuers. They are specified in exactly the same way,
but they do not belong to a single namespace and can be referenced by Certificate resources from
multiple different namespaces.
```
lets-encrypt-cluster-issuers.yaml:
```
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
name: letsencrypt-staging-issuer
spec:
acme:
# You must replace this email address with your own.
# Let's Encrypt will use this to contact you about expiring
# certificates, and issues related to your account.
email: user@example.com
server: https://acme-staging-v02.api.letsencrypt.org/directory
privateKeySecretRef:
# Secret resource that will be used to store the account's private key.
name: letsencrypt-staging-account-key
# Add a single challenge solver, HTTP01 using nginx
solvers:
- http01:
ingress:
class: nginx
---
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
name: letsencrypt-prod-issuer
spec:
acme:
# The ACME server URL
server: https://acme-v02.api.letsencrypt.org/directory
# Email address used for ACME registration
email: user@example.com
# Name of a secret used to store the ACME account private key
privateKeySecretRef:
name: letsencrypt-prod-account-key
# Enable the HTTP-01 challenge provider
solvers:
- http01:
ingress:
class: nginx
---
apiVersion: v1
kind: Secret
metadata:
name: tsig-dyn-update-secret
namespace: cert-manager
type: Opaque
data:
key: BASE64 encoded of BASE64 encoded (double-base64) TSIG-key
---
apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
name: letsencrypt-dns01-issuer
spec:
acme:
email: user@example.com
server: https://acme-v02.api.letsencrypt.org/directory
privateKeySecretRef:
# Secret resource that will be used to store the account's private key.
name: letsencrypt-dns01-account-key
# Add a single challenge solver, HTTP01 using nginx
solvers:
- dns01:
rfc2136:
nameserver: ip_address_of_your_authoritative_nameserver:nameserver_port
tsigKeyName: name_of_tsig_key_in_your_authoritative_nameserver
tsigAlgorithm: HMACSHA512
tsigSecretSecretRef:
name: tsig-dyn-update-secret
key: key
selector:
dnsZones:
- 'int.example.org'
```
`kubectl apply -f lets-encrypt-cluster-issuers.yaml`
## Deploying a LE-certificate with ingress <a name="user-content-cert-manager-ingress"></a>
All you need is an `Ingress` resource of class `nginx` which references a ClusterIssuer (`letsencrypt-prod-issuer`) resource.
HTTP-01 solver (`cert-manager.io/cluster-issuer: "letsencrypt-prod-issuer"`):
```
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
namespace: <stage>
name: some-ingress-name
annotations:
# use the shared ingress-nginx
kubernetes.io/ingress.class: "nginx"
cert-manager.io/cluster-issuer: "letsencrypt-prod-issuer"
spec:
tls:
- hosts:
- some-certificate.name.san
secretName: target-certificate-secret-name
rules:
- host: some-certificate.name.san
http:
paths:
- path: /
backend:
serviceName: some-target-service
servicePort: some-target-service-port
```
DNS-01 solver (`cert-manager.io/cluster-issuer: "letsencrypt-dns01-issuer"`):
```
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
namespace: <stage>
name: some-ingress-name
annotations:
# use the shared ingress-nginx
kubernetes.io/ingress.class: "nginx"
cert-manager.io/cluster-issuer: "letsencrypt-dns01-issuer"
spec:
tls:
- hosts:
- some-certificate.name.san
secretName: target-certificate-secret-name
rules:
- host: some-certificate.name.san
http:
paths:
- path: /
backend:
serviceName: some-target-service
servicePort: some-target-service-port
```
## Deploying a LE-certificate by CRD <a name="user-content-cert-manager-crd"></a>
All you need is a Certificate-CRD (Custom Resource Definition) like this one:
```
apiVersion: cert-manager.io/v1
kind: Certificate
metadata:
name: some-certificate
namespace: staging
spec:
# Secret names are always required.
secretName: some-secret
duration: 2160h # 90d
renewBefore: 360h # 15d
# The use of the common name field has been deprecated since 2000 and is
# discouraged from being used.
commonName: some.fully.qualified.domain.name
isCA: false
privateKey:
algorithm: RSA
encoding: PKCS1
size: 4096
usages:
- server auth
- client auth
# At least one of a DNS Name, URI, or IP address is required.
dnsNames:
- some.fully.qualified.domain.name
# Issuer references are always required.
issuerRef:
name: <your-favourite-cluster-issuer>
# We can reference ClusterIssuers by changing the kind here.
# The default value is Issuer (i.e. a locally namespaced Issuer)
kind: ClusterIssuer
```
After the certificate was issued, you can reference it as a volume within a deployment:
```
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: nginx-ssl
name: nginx-ssl
namespace: staging
spec:
replicas: 1
selector:
matchLabels:
app: nginx-ssl
strategy:
type: Recreate
template:
metadata:
labels:
app: nginx-ssl
spec:
volumes:
- name: nginx-ssl-volume
secret:
secretName: some-secret
containers:
- image: nginx
name: nginx-ssl
volumeMounts:
- mountPath: "/etc/nginx/ssl"
name: nginx-ssl-volume
readOnly: true
ports:
- containerPort: 80
restartPolicy: Always
```
## Troubleshooting <a name="user-content-cert-manager-troubleshooting"></a>
Docs: https://cert-manager.io/docs/faq/acme/
ClusterIssuer runs in default namespace:
```
kubectl get clusterissuer
kubectl describe clusterissuer <object>
```
All other ingres-specific cert-manager resources are running <stage> specific namespaces:
```
kubectl -n <stage> get certificaterequest
kubectl -n <stage> describe certificaterequest <object>
kubectl -n <stage> get certificate
kubectl -n <stage> describe certificate <object>
kubectl -n <stage> get secret
kubectl -n <stage> describe secret <object>
kubectl -n <stage> get challenge
kubectl -n <stage> describe challenge <object>
```
After successfull setup perform a TLS-test: `https://www.ssllabs.com/ssltest/index.html`
# HELM charts <a name="user-content-helm"></a>
Docs:
* https://helm.sh/docs/intro/using_helm/
Prerequisites:
* running kubernetes installation
* kubectl with ENV[KUBECONFIG] pointing to appropriate config file
* helm
## Create a chart <a name="user-content-helm-create"></a>
`helm create helm-test`
```
~/kubernetes/helm$ tree helm-test/
helm-test/
├── charts
├── Chart.yaml
├── templates
│   ├── deployment.yaml
│   ├── _helpers.tpl
│   ├── hpa.yaml
│   ├── ingress.yaml
│   ├── NOTES.txt
│   ├── serviceaccount.yaml
│   ├── service.yaml
│   └── tests
│   └── test-connection.yaml
└── values.yaml
```
## Install local chart without packaging <a name="user-content-helm-install-without-packaging"></a>
`helm install helm-test-dev helm-test/ --set image.tag=latest --debug --wait`
or just a *dry-run*:
`helm install helm-test-dev helm-test/ --set image.tag=latest --debug --dry-run`
```
--wait: Waits until all Pods are in a ready state, PVCs are bound, Deployments have minimum (Desired minus maxUnavailable)
Pods in ready state and Services have an IP address (and Ingress if a LoadBalancer) before marking the release as successful.
It will wait for as long as the --timeout value. If timeout is reached, the release will be marked as FAILED. Note: In
scenarios where Deployment has replicas set to 1 and maxUnavailable is not set to 0 as part of rolling update strategy,
--wait will return as ready as it has satisfied the minimum Pod in ready condition.
```
## List deployed helm charts <a name="user-content-helm-list"></a>
```
~/kubernetes/helm$ helm list
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
helm-test-dev default 4 2020-08-27 12:30:38.98457042 +0200 CEST deployed helm-test-0.1.0 1.16.0
```
## Upgrade local chart without packaging <a name="user-content-helm-upgrade"></a>
```
~/kubernetes/helm$ helm upgrade helm-test-dev helm-test/ --set image.tag=latest --wait --timeout 60s
Release "helm-test-dev" has been upgraded. Happy Helming!
NAME: helm-test-dev
LAST DEPLOYED: Thu Aug 27 12:47:09 2020
NAMESPACE: default
STATUS: deployed
REVISION: 7
NOTES:
1. Get the application URL by running these commands:
export POD_NAME=$(kubectl get pods --namespace default -l "app.kubernetes.io/name=helm-test,app.kubernetes.io/instance=helm-test-dev" -o jsonpath="{.items[0].metadata.name}")
echo "Visit http://127.0.0.1:8080 to use your application"
kubectl --namespace default port-forward $POD_NAME 8080:80
```
`helm upgrade [...] --wait` is synchronous and exit with 0 on success, otherwise with >0 on failure. `helm upgrade` will wait for 5 minutes Setting the `--timeout` (Default 5 minutes) flag makes This can be used in term of CI/CD deployments with Jenkins.
## Get status of deployed chart <a name="user-content-helm-status"></a>
```
~/kubernetes/helm$ helm status helm-test-dev
NAME: helm-test-dev
LAST DEPLOYED: Thu Aug 27 12:47:09 2020
NAMESPACE: default
STATUS: deployed
REVISION: 7
NOTES:
1. Get the application URL by running these commands:
export POD_NAME=$(kubectl get pods --namespace default -l "app.kubernetes.io/name=helm-test,app.kubernetes.io/instance=helm-test-dev" -o jsonpath="{.items[0].metadata.name}")
echo "Visit http://127.0.0.1:8080 to use your application"
kubectl --namespace default port-forward $POD_NAME 8080:80
```
## Get deployment history <a name="user-content-helm-history"></a>
```
~/kubernetes/helm$ helm history helm-test-dev
REVISION UPDATED STATUS CHART APP VERSION DESCRIPTION
10 Thu Aug 27 12:56:33 2020 failed helm-test-0.1.0 1.16.0 Upgrade "helm-test-dev" failed: timed out waiting for the condition
11 Thu Aug 27 13:08:34 2020 superseded helm-test-0.1.0 1.16.0 Upgrade complete
12 Thu Aug 27 13:09:59 2020 superseded helm-test-0.1.0 1.16.0 Upgrade complete
13 Thu Aug 27 13:10:24 2020 superseded helm-test-0.1.0 1.16.0 Rollback to 11
14 Thu Aug 27 13:23:22 2020 failed helm-test-0.1.1 blubb Upgrade "helm-test-dev" failed: timed out waiting for the condition
15 Thu Aug 27 13:26:43 2020 pending-upgrade helm-test-0.1.1 blubb Preparing upgrade
16 Thu Aug 27 13:27:12 2020 superseded helm-test-0.1.1 blubb Upgrade complete
17 Thu Aug 27 14:32:32 2020 superseded helm-test-0.1.1 Upgrade complete
18 Thu Aug 27 14:33:58 2020 superseded helm-test-0.1.1 Upgrade complete
19 Thu Aug 27 14:36:49 2020 failed helm-test-0.1.1 cosmetics Upgrade "helm-test-dev" failed: timed out waiting for the condition
```
## Rollback <a name="user-content-helm-rollback"></a>
`helm rollback helm-test-dev 18 --wait`
```
~/kubernetes/helm$ helm history helm-test-dev
REVISION UPDATED STATUS CHART APP VERSION DESCRIPTION
10 Thu Aug 27 12:56:33 2020 failed helm-test-0.1.0 1.16.0 Upgrade "helm-test-dev" failed: timed out waiting for the condition
11 Thu Aug 27 13:08:34 2020 superseded helm-test-0.1.0 1.16.0 Upgrade complete
12 Thu Aug 27 13:09:59 2020 superseded helm-test-0.1.0 1.16.0 Upgrade complete
13 Thu Aug 27 13:10:24 2020 superseded helm-test-0.1.0 1.16.0 Rollback to 11
14 Thu Aug 27 13:23:22 2020 failed helm-test-0.1.1 blubb Upgrade "helm-test-dev" failed: timed out waiting for the condition
15 Thu Aug 27 13:26:43 2020 pending-upgrade helm-test-0.1.1 blubb Preparing upgrade
16 Thu Aug 27 13:27:12 2020 superseded helm-test-0.1.1 blubb Upgrade complete
17 Thu Aug 27 14:32:32 2020 superseded helm-test-0.1.1 Upgrade complete
18 Thu Aug 27 14:33:58 2020 superseded helm-test-0.1.1 Upgrade complete
19 Thu Aug 27 14:36:49 2020 failed helm-test-0.1.1 cosmetics Upgrade "helm-test-dev" failed: timed out waiting for the condition
20 Thu Aug 27 14:37:36 2020 deployed helm-test-0.1.1 Rollback to 18
```
```
~/kubernetes/helm$ helm status helm-test-dev
NAME: helm-test-dev
LAST DEPLOYED: Thu Aug 27 14:37:36 2020
NAMESPACE: default
STATUS: deployed
REVISION: 20
NOTES:
1. Get the application URL by running these commands:
export POD_NAME=$(kubectl get pods --namespace default -l "app.kubernetes.io/name=helm-test,app.kubernetes.io/instance=helm-test-dev" -o jsonpath="{.items[0].metadata.name}")
echo "Visit http://127.0.0.1:8080 to use your application"
kubectl --namespace default port-forward $POD_NAME 8080:80
```
# Kubernetes in action <a name="user-content-kubernetes-in-action"></a>
## Running DaemonSets on `hostPort` <a name="user-content-running-daemonsets"></a>
* Docs: https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/
* Good article: https://medium.com/stakater/k8s-deployments-vs-statefulsets-vs-daemonsets-60582f0c62d4
In this case configuration of networking in context of services is not needed.
This setup is suitable for legacy scenarios where static IP-address are required and a NodePort service is not an alternative:
```
kind: DaemonSet
apiVersion: apps/v1
metadata:
name: netcat-daemonset
labels:
app: netcat-daemonset
spec:
selector:
matchLabels:
app: netcat-daemonset
template:
metadata:
labels:
app: netcat-daemonset
spec:
containers:
- command:
- nc
- -lk
- -p
- "23456"
- -v
- -e
- /bin/true
env:
- name: DEMO_GREETING
value: Hello from the environment
image: dockreg-zdf.int.zwackl.de/alpine/latest/amd64:prod
imagePullPolicy: IfNotPresent
name: netcat-daemonset
ports:
- containerPort: 23456
hostPort: 23456
protocol: TCP
resources:
limits:
cpu: 500m
memory: 64Mi
requests:
cpu: 50m
memory: 32Mi
restartPolicy: Always
securityContext: {}
terminationGracePeriodSeconds: 30
updateStrategy:
rollingUpdate:
maxUnavailable: 1
type: RollingUpdate
```
## Running StatefulSet with NFS storage <a name="user-content-running-statefulset-nfs"></a>
* https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/
* [NFS dynamic volume provisioning deployed](#pv-nfs)
**Be careful:** *StatefulSets* are designed for stateful applications (like databases). To avoid split-brain scenarios StatefulSets behave as static as possible. If a node goes down, the StatefulSet controller will reschedule the pods to another nodes, which can meet the requirements! If you want to force a re-scheduling:
`kubectl delete pod web-1 --grace-period=0 --force`
More details on this can be found [here](https://kubernetes.io/docs/tasks/run-application/force-delete-stateful-set-pod/)
If you want DaemonSet-like Node-affinity with StatefulSets then read [this](https://medium.com/@johnjjung/building-a-kubernetes-daemonstatefulset-30ad0592d8cb)
```
---
apiVersion: v1
kind: Service
metadata:
name: nginx
labels:
app: nginx
spec:
ports:
- port: 80
name: web
clusterIP: None
selector:
app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: web
spec:
selector:
matchLabels:
app: nginx
serviceName: "nginx"
replicas: 2
template:
metadata:
labels:
app: nginx
spec:
terminationGracePeriodSeconds: 10
containers:
- name: nginx
image: nginx:alpine
ports:
- containerPort: 80
name: web
volumeMounts:
- name: nfs-backend
mountPath: /nfs-backend
volumeClaimTemplates:
- metadata:
name: nfs-backend
spec:
accessModes: [ "ReadWriteMany" ]
storageClassName: "nfs-client"
resources:
requests:
storage: 32Mi
```
## Services <a name="user-content-services"></a>
### Client-IP transparency and loadbalancing <a name="user-content-services-client-ip-transparency"></a>
```
apiVersion: v1
kind: Service
[...]
spec:
type: NodePort
externalTrafficPolicy: <<Local|Cluster>>
[...]
```
`externalTrafficPolicy: Cluster` (default) spreads the incoming traffic over all pods evenly. To achieve this the client ip-address must be source-NATted and therefore it´s not *visible* to the PODs.
`externalTrafficPolicy: Local` preserves the original client ip-address which is visible to the PODs. In any case (`DaemonSet` or `StatefulSet`) traffic remains on the Node which gets the traffic. In case of `StatefulSet` if more than one POD of a `ReplicaSet` is scheduled on the same Node, the workload gets balanced over all PODs on the same Node.
### Session affinity/persistence <a name="user-content-services-session-persistence"></a>
```
apiVersion: v1
kind: Service
[...]
spec:
type: NodePort
sessionAffinity: <<ClientIP|None>>
sessionAffinityConfig:
clientIP:
timeoutSeconds: 10
[]
```
Session persistence (`None` by default) is only supported on client ip-address. Cookie-stickiness or stickiness on any other/higher layer is not supported yet.
## What happens if a node goes down? <a name="user-content-what-happens-node-down"></a>
If a node goes down kubernetes marks this node as *NotReady*, but nothing else:
```
$ kubectl get node
NAME STATUS ROLES AGE VERSION
k3s-node2 Ready <none> 103d v1.19.5+k3s2
k3s-master Ready master 103d v1.19.5+k3s2
k3s-node1 NotReady <none> 103d v1.19.5+k3s2
$ kubectl get pod
NAME READY STATUS RESTARTS AGE
ds-test-5mlkt 1/1 Running 14 28h
my-nfs-client-provisioner-57ff8c84c7-p75ck 1/1 Running 0 31m
web-1 1/1 Running 0 26m
web-2 1/1 Running 0 26m
ds-test-c6xx8 1/1 Running 0 18m
ds-test-w45dv 1/1 Running 5 28h
```
Kubernetes supports [Pod-tolerations](https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration), which are per default configured with a *timeout* of `300s` (5 minutes!). This means, that affected Pods will *remain* for a timespan of 300s on a *broken* node before eviction takes place
```
$ kubectl -n <namespace> describe pod <pod-name>
[...]
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
[...]
```
To be more reactive Pod-tolerations can be configured as follows:
```
kind: Deployment or StatefulSet
apiVersion: apps/v1
metadata:
[...]
spec:
[...]
template:
[...]
spec:
tolerations:
- key: "node.kubernetes.io/unreachable"
operator: "Exists"
effect: "NoExecute"
tolerationSeconds: 30
- key: "node.kubernetes.io/not-ready"
operator: "Exists"
effect: "NoExecute"
tolerationSeconds: 30
[...]
```
## Keep your cluster balanced <a name="user-content-keep-cluster-balanced"></a>
Kubernetes, in first place, takes care of high availability, but not of well balance of pod/node.
In case of `Deployment` or `StatefulSet` a `topologySpreadConstraint` needs to be specified:
```
kind: Deployment or StatefulSet
apiVersion: apps/v1
metadata:
[...]
spec:
[...]
template:
[...]
spec:
# Prevent to schedule more than one pod per node
topologySpreadConstraints:
- labelSelector:
matchLabels:
app: {{ .Chart.Name }}-{{ .Values.stage }}
maxSkew: 1
topologyKey: kubernetes.io/hostname
whenUnsatisfiable: DoNotSchedule
[...]
```
`DaemonSet` workloads do not support `topologySpreadConstraints` at all.
## Node maintenance <a name="user-content-node-maintenance"></a>
*Mark* a node for maintenance:
```
$ kubectl drain k3s-node2 --ignore-daemonsets
$ kubectl get node
NAME STATUS ROLES AGE VERSION
k3s-node1 Ready <none> 105d v1.19.5+k3s2
k3s-master Ready master 105d v1.19.5+k3s2
k3s-node2 Ready,SchedulingDisabled <none> 105d v1.19.5+k3s
```
All Deployment as well as StatefulSet pods have been rescheduled on remaining nodes. DaemonSet pods were not touched! Node maintenance can be performed now.
To bring the maintained node back in cluster:
```
$ kubectl uncordon k3s-node2
node/k3s-node2 uncordoned
```
## Dealing with disruptions <a name="user-content-disruptions"></a>
* https://kubernetes.io/docs/concepts/workloads/pods/disruptions/
* https://kubernetes.io/docs/tasks/administer-cluster/safely-drain-node/
# Troubleshooting <a name="user-content-troubleshooting"></a>
## Deleting a stuck namespace <a name="user-content-ts-delete-stuck-namespace"></a>
```
kubectl get namespace "stucked-namespace" -o json \
| tr -d "\n" | sed "s/\"finalizers\": \[[^]]\+\]/\"finalizers\": []/" \
| kubectl replace --raw /api/v1/namespaces/stucked-namespace/finalize -f -
```
## Deleting stuck CRDs <a name="user-content-ts-delete-stuck-crd"></a>
https://github.com/kubernetes/kubernetes/issues/60538#issuecomment-369099998
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