CKA 筆記 [7,8,9]: Security, Storage, Networking

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2024-05-20 2968 words 14 minutes views

Contents

Section 7 Security

TLS Basics

確保用戶跟Server之間的通訊是加密的

Symmetric Encryption: 加解密用同一支密鑰，必須在sender跟receiver之間交換，Hacker解密數據的風險較高。

Asymmetric Encryption:

Private Key: 用密鑰解密
Public Lock: 用公鎖加密
```
ssh-keygen
id_rsa  id_rsa.pub
```

PKI - Public Key Infrastructure

Solution Certificates API [Lab]

pwd
ls
cat akshay.csr
cat akshay.csr | base64 
# prints a single line 
cat akshay.csr | base64 -w 0
# create certificate signing request
cat > akshay.yaml
vi akshay.csr
vi akshay.yaml

kubectl create -f akshay.yaml
  certificatesigningrequest.certificates.k8s.io/akshay created
kubectl get csr
kubectl certificate approve akshay
kubectl get csr agent-smith -o yaml
kubectl certificate deny agent-smith
kubectl get csr
kubectl delete csr agent-smith

Create certificate signing request

akshay.yaml

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apiversion: certificates.k8s.io/v1
kind: CertificateSigningRequest
metadata:
  name: akshay
spec:
  request: # paste the single line
  signerName: kubernetes.io/kube-apiserver-client
  # expirationSeconds: 86400 # one day
  usages:
  - client auth

Kubeconfig

kubectl get pods
    --server my-kube-playground:6443
    --client-key admin.key
    --client-certificate admin.crt
    --certificate-authority ca.cr

Move above information into a kubeconfig file
$HOME/.kube/config
format:
- Clusters
  - Development
  - Production
  - Google
  - MyKubePlayground
- Contexts
  - Admin@Production
  - Dev@Google
  - MyKubeAdmin@MyKubePlayground
- Users
  - Admin
  - Dev User
  - Prod User
  - MyKubeAdmin

example:

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apiVersion: v1
kind: Config

current-context: dev-user@google

clusters:
- name:
  cluster: my-kube-playground
    certificate-authority: ca.crt
    server: https://my-kube-playground:6443
- name: development
- name: production
- name: google

contexts:
- name: my-kube-admin@my-kube-playground
  context:
    cluster: my-kube-playground
    user: my-kube-admin
    namespaces: finaces
- name: dev-user@google
- name: prod-user@production

users:
- name: my-kube-admin
  user:
    client-certificate: admin.crt
    client-key: admin.key
- name: admin
- name: dev-user
- name: prod-user

cluster -> users -> contexts user current-context

commands:

kubectl config view
kubectl config view --kubeconfig=my-kube-config
# 變更context
kubectl config use-context prod-user@production
kubectl config -h

namespaces (specified in context)
usecertificate-authority-data(optionally, providing the content) as alternative to certificate-authority (specifying path)
- cat ca.crt | base64
- 要貼上去的content須base64編碼過

Solution Kubeconfig

echo $HOME
ls .kube/
ls .kube//config
kubectl config view
kubectl get nodes

API Groups

curl https://kube-master:6443/version     # version
curl https://kube-master:6443/api/v1/pods # api

Multiple groups
- /metrics
- /healthz
- /version
- /api core group
  - /api/v1/{sub-group}, example of sub-group: namespaces, pods, rc, events endpoints, nodes, bindings, PV, PVC, configmaps, secrets, services
- /apis named group
  - API Groups: apps, extensions, networking.k8s.io, storage.k8s.io, authentication.k8s.io, certificates.k8s.io
    - /apis/apps/{version}/{resources}:
      - /deployments
        
        list of actions associated with it, such as list, get, create, delete, update, watch (verb)
      - /replicasets
      - /statefulsets
    - /apis/extensions/{version}/{resources}:
      - /networkpolicies
    - /apis/networking.k8s.io/{version}/{resources}:
    - /apis/storage.k8s.io/{version}/{resources}:
    - /apis/authentication.k8s.io/{version}/{resources}:
    - /apis/certificates.k8s.io/{version}/{resources}:
      - /certificatesigningrequests
- /logs

# to list all the available paths
curl http://localhost:6443 -k

curl http://localhost:6443/apis -k | grep "name"

curl http://localhost:6443 -k
    --key admin.key
    --cert admin.crt
    --cacert ca.crt

Lauch kubectl proxy on 127.0.0.1:8001

Kube proxy
- to enable connectivity between pods and services across different nodes in the cluster
Kubectl proxy
- An ACTP proxy service created by Kubectl

Authorization

Authorization mechanism:

Node
- Node authorizer

ABAC (attribute-based authorization)

can view/can create/can delete

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{
    "kind": "Policy", 
    "spec": {
        "user": "dev-user", 
        "namespace": "*", 
        "resource": "pods", 
        "apiGroup": "*"}
}

RBAC (role-based authorization)
- Instead of directly associating an user or group with a set of permissions, we define a role with a set of permissions required for developers, then associate all dev-users to that role.
- More standard approach to manage access withing K8S cluster
Webhook
- Outsource all mechanism
- Open Policy Agent
AlwaysAllow
AlwaysDeny

RBAC

Role:

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: developer
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["list", "get", "create", "update", "delete"]
- apiGroups: [""]
  resources: ["ConfigMap"]
  verbs: ["create"]

RoleBinding:

links an user object to a role
kubectl create -f devuser-developer-binding.yaml

apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: devuser-developer-binding
subjects:
- kind: User
  name: dev-user
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: Role
  name: developer
  apiGroup: rbac.authorization.k8s.io

View RBAC

kubectl get roles
kubectl get rolebinding
kubectl describe rolebinding devuser-developer-binding

Check Access

use the kubectl auth can i command to check if you can take certain actions
```
kubectl auth can-i create deployments
kubectl auth can-i delete nodes
```

if you are an administrator, you can impersonate:

 kubectl auth can-i create deployments --as dev-user
 yes
 kubectl auth can-i create pods --as dev-user --namespace test
 no

Solution Role based access controls

commands

cat /etc/kubernetes/manifests/kube-apiserver.yaml
ps -aux | grep authorization

k get roles
k get roles -A 
k get roles -A --no-headers
# wordcount
k get roles -A --no-headers | wc -l

k describe role kube-proxy -n kube-system

k get rolebindings -n kube-system
k describe rolebindings kube-proxy -n kube-system

k config view
k get pods --as dev-user 
k create role --help
k create role developer \
    --verb=list,create,delete
    --resource=pods
k describe role developer

k create rolebinding --help
k create rolebinding dev-user-binding \
    --role=developer
    --user=dev-user
k describe rolebinding dev-user-binding

k --as dev-user get pod dark-blue-app -n blue
pod "dark-blue-app" is forbidden
k get roles -n blue
k get rolebindings -n blue
k describe role developer -n blue

k edit role developer -n blue
# change resrouceNames into dark-blue-app
k --as dev-user get pod dark-blue-app -n blue

k --as dev-user create deployment nginx --image=nginx -n blue
k edit role developer -n blue
# add another rules, apiGroups: "apps", resources: deployments

Cluster Roles and cluster rolebindings

namespaced v.s. cluster scoped

namespaced
- if not specified, default namespace is used
- resources:
  - pods
  - replicasets
  - jobs
  - deployments
  - services
  - secrets
  - roles
  - rolebindings
  - configmaps
  - PVC
cluster scoped
- resources:
  - nodes
  - PV (persistent volumes)
  - clusterroles
  - clusterrolebindings
  - certificatesigningrequests
  - namespaces

clusterRole -> clusterRoleBinding

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: cluster-administrator
rules:
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["list", "get", "create", "delete"]

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: cluster-admin-role-binding
subjects:
- kind: User
  name: cluster-admin
  apiGroup: rbac.authorization.k8s.io
roleRef:
  kind: ClusterRole
  name: cluster-administrator
  apiGroup: rbac.authorization.k8s.io

Solution cluster roles

commands used

k get clusterroles
k get clusterroles --no-headers | wc -l #wordcount newlines

k get clusterrolebindings --no-headers | wc -l 
k get clusterrolebindings | grep cluster-admin
k describe clusterrolebindings cluster-admin

k describe clusterrole cluster-admin
# *.* stands for any and all resources

k get nodes --as michelle
k create clusterrole --help
k create clusterrole michelle-role \
    --verb=get,list,watch \
    --resource=nodes
    
k create clusterrolebinding --help
k create clusterrolebinding michelle-role-binding \
    --clusterrole=michelle-role \
    --user=michelle 
    
k describe clusterrole michelle-role
k describe clusterrolebinding michelle-role-binding

kubectl api-resources
# lists all the resrources as well as their short names

k create clusterrole storage-admin \
    --resource=persistentvolumes,storageclasses \
    --verb=list,create,get,watch
k describe clusterrole storage-admin

k get clusterrole storage-admin -o yaml
k create clusterrolebinding michelle-storage-admin \
    --user=michelle \
    --clusterrole=storage-admin
    
k describe clusterrolebinding michelle-storage-admin
k --as michelle get storageclass

Service Accounts

Two types of accounts: user account, service account
- user account: human
- service account: used by application to interact with k8s, such as Prometheus and Jenkins
When a service account is created, a service account token is created automatically

k create serviceaccount dashboard-sa
k get serviceaccrount
k describe servicearrount dashboard-sa
...
Tokens:    dashboard-sa-token-kbbdm

For every namespace in kubernetes, a service account named default is automatically created.
Whenever a pod is created, the default service account and its token are automatically mounted to that pod as a volume mount.

kubectl exec -it my-kubernetes-dashboard -- ls /var/run/secrets/kubernetes.io/serviceaccount`

kubectl exec -it my-kubernetes-dashboard cat /var/run/secrets/kubernetes.io/serviceaccount/token

If you’d like to use a different service account such as the one we just created, modify the pod definition file to include a service account field:

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apiVersion: v1
kind: Pod
metadata:
  name: my-kubernetes-dashboard
spec:
  containers:
    - name: my-kubernetes-dashboard
      image: my-kubernetes-dashboard
  serviceAccountName: dashboard-sa

You cannot modify the service account of an existing pod. You must delete and recreate the pod.

Solution Security

commands

kubectl create secret
kubectl get deploy
kubectl describe deploy web
k edit deploy web
# modify image and save
k describe deploy web
k get pods

k create secret docker-registry -h
k create secret docker-registry private-reg-cred \
    --docker-server=myprivateregistry.com:5000 \
    --docker-username=dock_user \
    --docker-password=dock_password \
    [email protected]

k get po

Docker Security

Docker implements linux capabilities. Please refer to /usr/include/linux/capability.h docker run --privileged docker run --cap-add docker run --cap-drop

Security Context

In K8S, containers are encapsulated in pod.
If you configure setting on both container and pod, the setting on the container will override the setting on the pod.

apiVersion: v1
kind: Pod
metadata: 
  name: web-pod
spec:
  # pod level 
  securityContext:
    runAsUser: 1000
    
  containers:
       - name: ubuntu
         image: ubuntu
         command: ["sleep", "3600"]
         # container level
         securityContext:
           runAsUser: 1000
           capabilities:
               add: ["MAC_ADMIN"]

Solution

command

whami

k get pod
k exec ubuntu-sleeper -- whoami
kubectl get pod ubuntu-sleeper -o yaml > ubuntu-sleeper.yaml
vi ubuntu-sleeper.yaml
kubectl delete pod ubuntu-sleeper --force
k apply -f ubuntu-sleeper.yaml
k get pod

Network Policies

Traffic
- ingress: incoming from user
- egress: outgoing request to database server

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: db-policy

spec:
  podSelector:
    matchLabels:
      role: db
  policyTypes:
  - Ingress
  ingress:
  - from:
    - podSelector:
        matchLabels:
          name: api-pod
    ports:
    - protocol: TCP
      port: 3306

Note:

Solutions that support network policies:
- Kube-router
- Calico
- Romana
- Weave-net
Solutions that do not support network policies:
- Flannel

Developing network policies

Pod selector: to select pods by labels
namespace selector: to select namespaces by labels
ipBlock selector: to select ip ranges

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: db-policy
spec: 
  podSelector:
    matchLabels:
      role: db 
  policyTypes:
  - Ingress
  
  ingress:
  - from:
    # Traffic coming from either pod/namespace or certain IP are allowed to passthrough
    # Within the first rule, we have two selectors and traffic of thid kind must meet both selectors. 
    # If added dash - before the namespaceSelector, these become three traffic rules.
    - podSelector:
          matchLabels:
            name: api-pod
      namespaceSelector:
          matchLabels:
            name: prod
    - ipBlock:
          cidr: 192.168.5.10/32 
    ports:
    - protocol: TCP
      port: 3306
      
  egress:
  - to:
    - ipBlock:
          cidr: 192.168.5.10/32
    ports: 
    - protocol: TCP
      port: 80

Solution network policies

commands

alias k=kubectl
k get pods
k get service
k get networkpolicies
k get netpol
k describe netpol payroll-policy
vi internalpolicy.yaml

internalpolicy.yaml

Policy name: internal-policy
Policy Type: Egress
Egress Allow: payroll
Payroll Port: 8080
Egress Allow: mysql

MySQL Port: 3306

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-network
  namespace: default
spec:
  podSelector:
    matchLabels:
      role: db
  policyTypes:
    -Ingress
    -Egresss

Section 8 Storage

This chapter covers storage such as persistent volumes, persistent volume claims, configure App with persistent storage, access modes for volumes, Kubernetes storage object, etc.

Two concepts of storages in Docker: Storage driver, Volume driver

Storage in Docker

File system
- /var/lib/docker
  - aufs
  - containers
  - image
  - volumes

Layered architecture

當Docker build images的時候，是以分層式架構(layered architecture) build image

Dockfile example

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# layer 1. base ubuntu layer
FROM Ubuntu
# layer 2. changes in apt packages
RUN apt-get update && apt-get -y install python
# layer 3. changes in pip packages
RUN pip install flask flask-mysql
# layer 4. source code
COPY . /opt/source-code
# layer 5. update entrypoint
ENTRYPOINT FLASK_APP=/opt/source-code/app.py flask run

docker build Dockerfile -t wycwyz/custom-app
如果前三行使用的作業系統跟dependencies一樣，就會用cache裡面的，減少build image所需時間，也節省disk space
以上的 layer 1 ~ layer 5 都是 Read Only (image layers)
Layer 6 (container layer) 則是 Read Write

Copy on Write mechanism
- 如果連進container要修改程式，會先從image layer複製一份到container layer，原本的image不會異動，除非用 docker rebuild
- 在刪掉container之後，container的暫存layer也會被刪掉
Volumes
- 保留由 container 建立的數據
- /var/lib/docker/volumes/data_volume
```
docker run -v data_volume:/var/lib/mysql mysql
docker run -v data_volume2:/var/lib/mysql mysql
docker run -v /data/mysql:/var/lib//mysql mysql
```
- 兩種類型的掛載(mounting):
  1. Volume mounting 卷掛載
    - mounts volume from the volume directory
  2. Bind mount 綁定掛載
    - mounts a directory from any location on the Docker host (在Docker主機的任何位置掛載)
- 舊的flag-v、新版用-mount方法或--mount(best)
```
docker run \
  --mount type=bind,source=/data/mysql,target=/var/lib/mysql mysql
```
Storage Driver:
- 工作內容:
  - 維護 layered architecture
  - 創建 writable layer
  - 跨層移動文件來實現 copy and write
- 常見存儲驅動程序
  - AUFS
  - ZFS
  - BTRFS
  - Device Mapper
  - Overlay
  - Overlay2

Storage Drivers

Storage driver 不處理 volume，而是由 Volume driver 處理 volume
- 常見Storage driver: AUFS, ZFS, BTRFS, DEVICE MAPPER, OVERLAY
預設的 volume driver 是Local，還有其他選項
- 常見Volume driver: Local, Azure File Storage, Convoy, DigitalOcean Block Storage, Flocker, gce-docker, GlusterFS, NetApp, RexRay, Portworx, VMware vSphere Storage
  - RexRay: 適用於AWS EBS, EMC, Google Persistent Disk, OpenStack Cinder

Run volume driver 的時候指定類型把資料持久化的儲存在AWS cloud，當container exit時，資料存雲端

docker run -it \
    --name mysql
    --volume-driver rexray/ebs
    --mount src=ebs-vol,target=/var/lib/mysql \
    mysql

Container Storage Interface (CSI)

以前，K8s的container runtime engine只有Docker，所有跟Docker交互的程式都刻在Kubernetes源碼。

後來隨著其他container runtimes (例如: rkt, cri-o) 的出現，再用相同的embedded方法不太適合，因此出現了Container Runtime Interface。

Container Networking Interface (CNI)
- flannel, cilium, weaveworks
Container Storage Interface (CSI)
- portworx, Amazon EBS, DELL EMC, GlusterFS
- 可以自建driver來讓你的storage與K8s交互

Volumes

Docker container is meant to be transient in nature.
To attached persistent data to container, we attach a volume to the containers when they are created.
Pod created in K8s is transcient. The data generated by pod is stored in volume.

apiVersion: v2
kind: Pod
metadata:
  name: random-number-generator
spec:
  containers:
  - image: alpine
    name: alpine
    command: ["/bin/sh", "-c"]
    args: ["shut -i 0-100 -n 1 >> /opt/number.out"]
    volumeMounts:
    - mountPath: /opt
      name: data-volume
    
  volumes:
  - name: data-volume
    hostPath:
      path: /data
      type: Directory

Persistent Volumes

在先前提的volume中，Volume是定義在pod definition file，但如果你很多個PODS，這樣所有的PODS都需要做這些配置，若一有變更，所有的pod definition files都需要跟著修改，為了中心化管理，可以用Persistent Volume達成
```
[Pod1]  [Pod2]  [Pod3]  [Pod4]
  |       |       |       |
  |       |       |       |
  [Peristent Volume Claim (PVC)]   
  |       |       |       |
[ [PVC]  [PVC]   [PVC]   [PVC] [] [] [] ]
       Persistent Volumes (PVs)
```

Base Template pv-definition.yaml

accessModes三種: ReadOnlyMany, ReadWriteOnce, ReadWriteMany

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apiVersion: v
kind: PersistentVolume
metadata:
  name: pv-voll
spec:
  accessModes:
      - ReadWriteOnce  
  capacity:
      storage: 1Gi
  hostPath:
      path: /tmp/data

kubectl create -f pv-definition.yaml
kubectl get persistentvolume

Persistent volume claims

Persistent Volume 以及 Persistent Volume Claim 是 K8s 命名空間裡面兩個不同的物件。管理員建立 persistent volume 的集合，使用者建立 persistent volume claims 來使用storage
一旦建立了 persistent volume claims，K8S 就會根據 request 以及 volume 設定的 properties，將 PV 綁定到相對應的 PVC
每個 PVC 綁定一個 PV
也可以用 label & selector 做綁定條件

Example of pvc-definition.yaml

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apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myclaim
spec:
  accessModes:
     - ReadWriteOnc

  resources:
     requests:
       storage: 500Mi

Example of pv-definition.yaml

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apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-voll
spec:
  accessModes:
      - ReadWriteOnce  
  capacity:
      storage: 1Gi
  awsElasticBlockStore:
    volumeID: <volume-id>
    fsType: ext4

刪除 PVCs
```
kubectl delete persistentvolumeclaims myclaim
```
- 刪除了之後，這個PVC預設會變成retain，指的是persistent volume仍然存在，直到管理員將volume刪除
```
persistentVolumeReclaimPolicy: Retain
```
- 可以調整設定讓persistent volume自動隨著pvc刪除而跟著刪掉釋放空間
```
persistentVolumeReclaimPolicy: Delete
```
- 另外一種Recycle指的是data volume的資料會被抹除，再給其它claim使用
```
persistentVolumeReclaimPolicy: Recycle
```

Solution PV and PVC

commands

k get pods
k exec webapp -- cat /log/app.log   #exec <pod-name> 
k get pods
k describe pod webapp 
ls /var/log/webapp
# set up volumes
k edit pod webapp

webapp-pod-definition.yaml

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...
spec:
  containers:
  - env:
    ...
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-lmntb
      readOnly: true
    # mount log
    - mountPath: /log
      name: log-volume
  ...
  volumes:
  - name: log-volume # add log volume
    hostPath:
       path: /var/log/webapp
  - name: kube-api-access-lmntb
    ...

commands

cd ~
vi pv-definition.yaml
k create -f pv.yaml
k get pv

pv-definition.yaml

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apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-log
spec:
  capacity:
    storage: 100Mi ✨Ref
  # volumeMode: Filesystem cmment不用
  accessModes:
    - ReadWriteMany 🎉Ref
  persistentVolumeReclaimPolicy: Retain
  hostPath:
    path: /pv/log

commands

vi pvc.yaml
k create -f pvc.yaml
k get pvc #check status

pvc.yaml

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apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: claim-log-1 🎆Ref
spec:
  accessModes:
    - ReadWriteMany 🎉Ref
  resources:
    requests:
      storage: 100Mi✨Ref

command

# To change the access modes on PVC, to rewritemany 
vi pvc.yaml
# delete and replace
k replace --force -f pvc.yaml
k get pv
k get pvc
# replace hostpath with PV
ls /pv/log
k edit pod webapp
k replace --force -f /tmp/kubectl-edit-56385166.yaml
ls /pv/log 
k get pv pv-log
k delete pvc 




k describe pvc claim-log-1
k delete pod webapp
k get pvc

webapp-pod-definition.yaml

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  ...
  volumes:
  - persistentVolumeClaim:
        claimName: claim-log-1 🎆Ref

Storage Class

Static Provisioning
- 從Google Cloud建立pv，在建立pv之前必須先在GoogleCloud手動建立disk，才能手動建立persistent volume
```
gcloud beta compute disks create pd-disk \
    --size 1GB --region us-east1
```

Dynamic Provisioning

建立以下template sc-definition.yaml

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apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
   name: google-storage 🎁Ref
provisioner: kubernetes.io/gce-pd

可以拔掉persistent volume，再來修pvc.yaml, pod.yaml

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apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: 

pv的設定在建立sc時就會隨之建立，所以不用pv.yaml

pvc-definition.yaml更新設定

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apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: claim-log-1 🎆Ref
spec:
  accessModes:
     - ReadWriteOnce
  storageClassName: google-storage 🎁Ref
  # 這樣pvc才知道要使用哪個StorageClass
  resources:
    requests:
      storage: 500Mi

這樣下次如果建立了一個pvc，與他關聯的sc就會使用defined provisioner來配置所需大小的new disk，然後建立 persistent volume並綁定pvc到這個volume
StorageClass 仍然會建立一個PV
有其它的provisioner，像是AWS EBS(elastic block store), AzureFile, AzureDisk, CephFS, Portworx, ScaleIO, etc.

每個provisioner可以傳入額外參數，例如要provision的磁碟類型、replication type 等等，以下是拿GCE為例

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# standard class
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
   name: silver
provisioner: kubernetes.io/gce-pd

parameters:
  type: pd-standard
---
# gold class: with ssd
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
   name: gold
provisioner: kubernetes.io/gce-pd

parameters:
  type: pd-ssd
  replication-type: none
---
# platinum class: with replication
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
   name: platinum
provisioner: kubernetes.io/gce-pd

parameters:
  type: pd-ssd
  replication-type: regional-pd

Solution Storage Class

command

k get storageclass
k get sc
# check volumebindingmode
k get pv
# RWO (accessmodes)
k get pvc
vi pvc.yaml
# paste below pv.yaml file
k create -f pvc.yaml
k get pvc
k describe pvc local-pvc
k run nginx --image=nginx:alpine --dry-run=client -o yaml
k run nginx --image=nginx:alpine --dry-run=client -o yaml > nginx.yaml
vi nginx.yaml
# paste below nginx configuration
k create -f nginx.yaml
k get pod
k get pvc
vi delayed-volume-sc.yaml
# paste below delayed-volume-sc.yaml
k create -f delayed-volume-sc.yaml

k get sc

example of pv.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: local-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 500Mi
  storageClassName: local-storage

regarding the nginx.yaml

apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: nginx
  name: nginx
spec:
  containers:
  - image: nginx:alpine
    name: nginx
    resources: {}
    volumeMount:
      - mountPath: "/var/www/html"
        name: local-pvc-volume
  dnsPolicy: ClusterFirst
  restartPolicy: Always
  volumes:
  - name: local-pvc-volume
    persistentVolumeClaim:
        claimName: local-pvc
status: {}

regarding the delayed-volume-sc.yaml

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: delayed-volume-sc
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

Section 9 Networking

This section focuses on the networking concepts.

Pre-requisites:
- Switching, Routing
- CoreDNS
- Tools
- DNS
- CNI
- Networking in Docker
Concepts:
- Networking configuration on cluster nodes
- POD networking concepts
- Service networking
- Cluster DNS
- Network loadbalancer
- Ingress

Linux Networking Basics: Switching, Routing

Networking pre-requisites
- Switching and Routing
  - Switching
  - Routing
  - Default Gateway
- DNS
  - DNS Configurations on Linux
  - CoreDNS Introduction
- Network Namespaces
- Docker Networking

Switching

ip link
ip addr add <ip_of_the_other_host>/24 dev eth0
ping <ip_of_the_switch>

Routing
- A router helps connect two networks together
- Think of it as another server with many network ports
Gateway
- 當systemB要傳封包到systemC，要如何知道這router在network哪裡，才能知道封包要往哪投，但network上面可能有很多這樣的devices，因此我們會用 Gateway 或 route 來配置系統
- 如果network比喻成房間，那麼gateway就是連到外部世界的門，會接到其它網路或連到外部網路

查看系統既有的routing configuration: route 增加一個route讓他連到network 2.0:
ip route add <network_2.0>/24 via <ip_of_host_B_of_1st_network>

增加一個路由條目:告訴host_A通往network_2的門/網關是通過host_B

ip route add <ip_address_to_network_2>/24 via <ip_from_A_to_host_B>

host_C同時也要找到如何傳回值的路徑，所以也要加route，透過host_B找到通往host_a的門

ip route add <ip_address_to_1st_network>/24 via <ip_from_C_to_host_B>

Take aways

ip link 用來列出和修改host主機上的interface
ip addr 用來查看分配給這些interface的IP address
ip addr add <ip_address>/24 dev eth0 用來在interface裡面設定IP address