Kubernetes - Storage - LAB - Day 11

 kubernetes - storage - LAB -> 1/28/2021

k8s -> Deployment -> Image (app) -> Launch POD

k8s
- Deployment
  - Image
    - Launch POD (APP)




[root@master jan26]# more mydeploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myweb-deploy

spec:
#  type: recreate
  replicas: 3
  selector:
    matchLabels:
      env: prod
    matchExpressions:
      - { key: team, operator: In, values: [ team1, team2 ]}
      - { key: tier, operator: In, values: [ frontend ] }
  template:
    metadata:
      name: "webpod4"
      labels:
        env: prod
        team: team1
        tier: frontend

    spec:
      containers:
      - name: "webc1"
        image: "vimal13/webserver-apache-php"




> kc get depploy
> kc get po
> kc apply -f pv-deploy
> kc get deploy
> kc expose deploy myd --port=80 --type=NodePort

> kc get scvc
> kc exec -it myd-.... -- bash

curl http://192.168.56.20:30518
hellow world !!!

# cd /var/www/html
# vi index.php
I made change to this file.

affaramal

> kc get po
> kc delete pod myd-....

since pod launch using deployment, it will re-launch again.


if you login inside this pod, your data is removed.

# cat /var/www/html/index.php


so, we have to manage the storage on permanenet basis.

kubernet -> persistance storage

Persistent volume
-----------------

> kc get po
> kc exec -it mdyd.... -- bash
# cd /var/www/html

mount path

PV -


-------------------------------------------
$ cat pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:    # give name to  your resource
  name: mypvc

spec:
  storageClassName: "" # you don't have to write static, only value needed for dynamic storage
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi


Storage type accss mode
- ReadWrite (RW) -
   - RWO - Read write o -> one read/write
   - RWX - read write many - multi cluster env
- ReadOnly (RO)


PVC
- Static PV
- Dynamic PV

Storage Class

static PV -> we don't use storage class


> kc apply -f pv-deploy
> kc get pod

> kc apply -f pv-deploy.yaml
> kc get pvc
> kc describe pvc myppvc


you see status pending ..

what happened here?
here the job of kubernetes admin team comes up...

They go to main storage (cloud, nas or local storage)
- they create a block of say 10 GB, access mode say rw
- they create a box and provide it (bound/binding)

after that status change from pending to bound

here, admin need to manually go and create a box/volume. this is called static PV.



k8s current architecture
-> single machine
   -> VM (Minikube)
      -> Master node
      -> Worker node


so, we are going to create a dir /mydir on worker node and and assign it to POD.


$ cat pv.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: mypv
spec:
  storageClassName: ""
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce


:> kc get pd
> kc get ppvc
> notepad pv.yaml
> kc get pvc
> kc get pv
you see bounded..
see under claim..


Open deployment file
---------------------
# more mydeploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myweb-deploy

spec:
#  type: recreate
  replicas: 3
  selector:
    matchLabels:
      env: prod
    matchExpressions:
      - { key: team, operator: In, values: [ team1, team2 ]}
      - { key: tier, operator: In, values: [ frontend ] }
  template:
    metadata:
      name: "webpod4"
      labels:
        env: prod
        team: team1
        tier: frontend

    spec:
      Volunes:        # You are defining on pod definition file.
      - name: mypod-pvc
        persistentVolumeClaim:            # specify PVC where it is coming from?
          claimname: mypvc
# you may have other pvc
#        persistentVolumeClaim:            # specify PVC where it is coming from?
#          claimname: mypvc2
      containers:
      - name: "webc1"
        image: "vimal13/webserver-apache-php"
        volumemounts:
          - mountPath: /var/www/html    # specify the mountpoint where you want to mount
            name: mypod-pvc    # the name of PVC

# you can have other containers as well.
# but you may use different pvc
#      - name: "webc2"
#        image: "httpd"
#        volumemounts:
#          /var/www/html1


clean the code
# more mydeploy.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myweb-deploy

spec:
#  type: recreate
  replicas: 3
  selector:
    matchLabels:
      env: prod

  template:
    metadata:
      name: "webpod4"
      labels:
        env: prod
        team: team1
        tier: frontend
----------------------------------------------- spec for volume
    spec:
      Volunes:        
      - name: mypod-pvc
        persistentVolumeClaim:
          claimname: mypvc

      containers:
      - name: "webc1"
        image: "vimal13/webserver-apache-php"
        volumemounts:
          - mountPath: /var/www/html
            name: mypod-pvc    


> kc apply
> kc describe
check under mounts

> kc get svc
> kurl 192.168.99.100:30534/index.html

Now, you don't see any output
The reason is that new storage replaced the old data.
now, everything you store on PVC, will be available

now, data is storeed on the host(node) where it is coming from
> kc get pods
> kc exec -it myd.---- -- bash

> cat > /var/www/html/index.html
New updated file

now curl again from the client side, you will see latest data.

> kc get svc
> kurl 192.168.99.100:30534/index.html

> kc get pvc
> kc get pv

> kc get pod
> kc delete pvc mypvc
it will not be deleted because it is used by POD.

to delete ppvc, delete pod. to delete pod, first delete deployment

> kc delete deployment    # everything will be deleted.


kc get pvc
it is also deleted.

deployment deleted

> kc get pv
now, status will shows released before when it was used it was on bound state.


reclaim policy
- recycle -> you can reuse
- retain  -> you cant re-use

Status
- released
- available
- bound


claim
- recycle


How to change it

reclaim policy

edit pw, on the fly - dynamically

> kc edit pv mypv
go down all the way down
and change to Recycle un der persistentVolumeRecaimPolicy

you will see recycle and status changed to available and claim is free...

in this process, we have to create PV manually.

admin need to go and check manually whether PVC request is there.

Now, dynamic comes on the play and storage class is used.



reclaim delete policy will remove the volume. You don't have to manually delete it.

1. create pvc
2. Create pv (attach)
3. Edit pod definition file
4. Create pod
5. Use the storage
6. Modify the files content
7. Delete the pod
8. Recreate a pod (use deployent, it will automatically creates on deletion)