App Lifecycle and Management

Updated Dec 29, 2023 ·

Some of the scenario questions here are based on Kodekloud's CKA course labs.

NOTE

CKAD and CKA can have similar scenario questions. It is recommended to go through the CKAD practice tests.

Shortcuts

First run the two commands below for shortcuts.

export do="--dry-run=client -o yaml" 
export now="--force --grace-period=0" 

Questions

Inspect the current deployment and determine the strategy used.

controlplane ~ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           84s  

Answer

controlplane ~ ➜  k describe deployments.apps frontend | grep -i strategy
StrategyType:           RollingUpdate
RollingUpdateStrategy:  25% max unavailable, 25% max surge

Upgrade the application by setting the image on the deployment to kodekloud/webapp-color:v2. Do not delete and re-create the deployment. Only set the new image name for the existing deployment.

Answer

controlplane ~ ➜  k edit deployments.apps frontend 
deployment.apps/frontend edited 

apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
    deployment.kubernetes.io/revision: "1"
creationTimestamp: "2023-12-29T17:01:17Z"
generation: 1
name: frontend
namespace: default
resourceVersion: "855"
uid: 05c0c824-dd8a-4f28-9c88-0f45cfd1702d
spec:
minReadySeconds: 20
progressDeadlineSeconds: 600
replicas: 4
revisionHistoryLimit: 10
selector:
    matchLabels:
    name: webapp
strategy:
    rollingUpdate:
    maxSurge: 25%
    maxUnavailable: 25%
    type: RollingUpdate
template:
    metadata:
    creationTimestamp: null
    labels:
        name: webapp
    spec:
    containers:
    - image: kodekloud/webapp-color:v2

controlplane ~ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   5/4     4            3           5m18s 

Up to how many PODs can be down for upgrade at a time. Consider the current strategy settings and number of PODs - 4

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6m30s 

Answer

controlplane ~ ✦ ➜  k describe deployments.apps frontend | grep -i unavailable
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
RollingUpdateStrategy:  25% max unavailable, 25% max surge

Change the deployment strategy to Recreate. Delete and re-create the deployment if necessary. Only update the strategy type for the existing deployment.

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6m30s 

Answer

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           6m30s

controlplane ~ ✦ ➜  k describe deployments.apps frontend | grep -i unavailable
Replicas:               4 desired | 4 updated | 4 total | 4 available | 0 unavailable
RollingUpdateStrategy:  25% max unavailable, 25% max surge 

controlplane ~ ✦ ➜  k edit deployments.apps frontend

apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
    deployment.kubernetes.io/revision: "2"
creationTimestamp: "2023-12-29T17:01:17Z"
generation: 2
name: frontend
namespace: default
resourceVersion: "1060"
uid: 05c0c824-dd8a-4f28-9c88-0f45cfd1702d
spec:
minReadySeconds: 20
progressDeadlineSeconds: 600
replicas: 4
revisionHistoryLimit: 10
selector:
    matchLabels:
    name: webapp
strategy:
    type: Recreate  

controlplane ~ ✦ ➜  k get deployments.apps 
NAME       READY   UP-TO-DATE   AVAILABLE   AGE
frontend   4/4     4            4           10m  

In the current pod, what is the command used to run the pod ubuntu-sleeper?

controlplane ~ ➜  k get po
NAME             READY   STATUS    RESTARTS   AGE
ubuntu-sleeper   1/1     Running   0          22s 

Answer

controlplane ~ ➜  k get po ubuntu-sleeper -o yaml | grep -i command -A 5
- command:
    - sleep
    - "4800"
    image: ubuntu
    imagePullPolicy: Always
    name: ubuntu 

Create a pod with the ubuntu image to run a container to sleep for 5000 seconds.

Answer

## ubuntu-sleeper-2.yaml 
apiVersion: v1
kind: Pod 
metadata:
name: ubuntu-sleeper-2
spec:
containers:
- name: ubuntu
    image: ubuntu
    command: 
    - "sleep"
    - "5000"

controlplane ~ ➜  k apply -f ubuntu-sleeper-2.yaml 
pod/ubuntu-sleeper-2 created

controlplane ~ ➜  k get po
NAME               READY   STATUS    RESTARTS   AGE
ubuntu-sleeper     1/1     Running   0          4m5s
ubuntu-sleeper-2   1/1     Running   0          4s 

Create a pod using the file named ubuntu-sleeper-3.yaml. There is something wrong with it. Try to fix it

## ubuntu-sleeper-3.yaml
apiVersion: v1 
kind: Pod 
metadata:
  name: ubuntu-sleeper-3 
spec:
  containers:
  - name: ubuntu
    image: ubuntu
    command:
    - "sleep"
    - 1200  

Answer

Commands should be enclosed in quotes.

## ubuntu-sleeper-3.yaml
apiVersion: v1
kind: Pod 
metadata:
name: ubuntu-sleeper-3
spec:
containers:
- name: ubuntu
    image: ubuntu
    command:
    - "sleep"
    - "1200"

controlplane ~ ✦2 ➜  k apply -f ubuntu-sleeper-3.yaml 
pod/ubuntu-sleeper-3 created

controlplane ~ ✦2 ➜  k get po
NAME               READY   STATUS    RESTARTS   AGE
ubuntu-sleeper     1/1     Running   0          11m
ubuntu-sleeper-2   1/1     Running   0          3m19s
ubuntu-sleeper-3   1/1     Running   0          25s 

Create a pod with the given specifications. By default it displays a blue background. Set the given command line arguments to change it to green.

Pod Name: webapp-green
Image: kodekloud/webapp-color
Command line arguments: --color=green

Answer

controlplane ~ ✦2 ➜  k run webapp-green --image  kodekloud/webapp-color $do -o yaml > green.yml

## green.yml
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
    run: webapp-green
name: webapp-green
spec:
containers:
- image: kodekloud/webapp-color
    name: webapp-green
    resources: {}
    args:
    - "--color"
    - "green"
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}
~              

controlplane ~ ✦2 ➜  k apply -f green.yml 
pod/webapp-green created

controlplane ~ ✦2 ➜  k get po
NAME               READY   STATUS    RESTARTS   AGE
ubuntu-sleeper     1/1     Running   0          21m
ubuntu-sleeper-2   1/1     Running   0          13m
ubuntu-sleeper-3   1/1     Running   0          8m50s
webapp-green       1/1     Running   0          3s

What is the environment variable name set on the container in the pod?

controlplane ~ ➜  k get po
NAME           READY   STATUS    RESTARTS   AGE
webapp-color   1/1     Running   0          19s 

Answer

controlplane ~ ➜  k describe po webapp-color | grep -i env -A 5
    Environment:
    APP_COLOR:  pink 

Identify the database host from the config map db-config.

controlplane ~ ✦ ➜  k get cm 
NAME               DATA   AGE
kube-root-ca.crt   1      13m
db-config          3      9s 

Answer

controlplane ~ ✦ ➜  k describe cm db-config 
Name:         db-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
DB_HOST:
----
SQL01.example.com
DB_NAME:
----
SQL01
DB_PORT:
----
3306

BinaryData
====

Events:  <none> 

Create a new ConfigMap for the webapp-color POD. Use the spec given below.

ConfigMap Name: webapp-config-map
Data: APP_COLOR=darkblue
Data: APP_OTHER=disregard

Answer

controlplane ~ ✦ ➜  k create cm webapp-config-map $do > webapp-color.yml

## webapp-color.yml
apiVersion: v1
kind: ConfigMap
metadata:
creationTimestamp: null
name: webapp-config-map
data:
APP_COLOR: "darkblue"
APP_OTHER: "disregard"
~                         

controlplane ~ ✦ ➜  k apply -f webapp-color.yml 
configmap/webapp-config-map created

controlplane ~ ✦ ➜  k get cm
NAME                DATA   AGE
kube-root-ca.crt    1      17m
db-config           3      4m56s
webapp-config-map   2      3s

controlplane ~ ✦ ➜  k describe cm webapp-config-map 
Name:         webapp-config-map
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
APP_OTHER:
----
disregard
APP_COLOR:
----
darkblue

BinaryData
====

Events:  <none> 

Update the environment variable on the POD to use only the APP_COLOR key from the newly created ConfigMap.

controlplane ~ ✦ ➜  k get po
NAME           READY   STATUS    RESTARTS   AGE
webapp-color   1/1     Running   0          8m 

Answer

controlplane ~ ✦ ➜  k get cm
NAME                DATA   AGE
kube-root-ca.crt    1      20m
db-config           3      7m53s
webapp-config-map   2      3m 

controlplane ~ ✦ ➜  k create cm webapp-config-map $do > webapp-color.yml

controlplane ~ ✦ ➜  k get po webapp-color -o yaml > color.yml

controlplane ~ ✦ ➜  k delete -f color.yml $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "webapp-color" force deleted

controlplane ~ ✦ ➜  k get po
No resources found in default namespace.

Follow the K8s docs on how to configure pods to use configmaps.

## color.yml 
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: "2023-12-29T17:36:54Z"
labels:
    name: webapp-color
name: webapp-color
namespace: default
resourceVersion: "781"
uid: 1e5515fa-9479-4ddd-a463-1df7723c1f8c
spec:
containers:
- env:
    - name: APP_COLOR
    valueFrom:
        configMapKeyRef:
        name: webapp-config-map
        key: APP_COLOR

controlplane ~ ✦ ➜  k apply -f color.yml 
pod/webapp-color created

controlplane ~ ✦ ➜  k get po
NAME           READY   STATUS    RESTARTS   AGE
webapp-color   1/1     Running   0          5s 

How many secrets are defined in the dashboard-token secret?

controlplane ~ ➜  k get secrets 
NAME              TYPE                                  DATA   AGE
dashboard-token   kubernetes.io/service-account-token   3      40s

Answer

controlplane ~ ➜  k describe secrets dashboard-token 
Name:         dashboard-token
Namespace:    default
Labels:       <none>
Annotations:  kubernetes.io/service-account.name: dashboard-sa
            kubernetes.io/service-account.uid: dec16229-5c52-414f-928d-28380a3fb4b3

Type:  kubernetes.io/service-account-token

Data
====
ca.crt:     570 bytes
namespace:  7 bytes
token:      eyJhbGciOiJSUzI1NiIsImtpZCI6IjlEc25IMUFwZ1pfZlRVcmVla3pvbS0yTXlsa1ZzT1RyZktaWmJCR1dYVHcifQ.eyJpc3MiOiJrdWJlcm5ldGVzL3NlcnZpY2VhY2NvdW50Iiwia3ViZXJuZXRlcy5pby9zZXJ2aWNl 

Create a new secret named db-secret with the data given below.

Secret Name: db-secret
Secret 1: DB_Host=sql01
Secret 2: DB_User=root
Secret 3: DB_Password=password123

Answer

controlplane ~ ➜  kubectl create secret generic db-secret \
    --from-literal='DB_Host=sql01' \
    --from-literal='DB_User=root' \
    --from-literal='DB_Password=password123' 

secret/db-secret created

controlplane ~ ➜  k get secret
NAME              TYPE                                  DATA   AGE
dashboard-token   kubernetes.io/service-account-token   3      8m18s
db-secret         Opaque                                3      23s

controlplane ~ ➜  k describe secrets db-secret 
Name:         db-secret
Namespace:    default
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
DB_Host:      5 bytes
DB_Password:  11 bytes
DB_User:      4 bytes 

Configure webapp-pod to load environment variables from the newly created secret (from the previous question).

Pod name: webapp-pod
Image name: kodekloud/simple-webapp-mysql
Env From: Secret=db-secret

Answer

controlplane ~ ➜  k get po
NAME         READY   STATUS    RESTARTS   AGE
webapp-pod   1/1     Running   0          6m55s
mysql        1/1     Running   0          6m55s

controlplane ~ ➜  k get po webapp-pod -o yaml > webapp-pod.yml

controlplane ~ ✦2 ➜  k delete -f webapp-pod.yml $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "webapp-pod" force deleted

controlplane ~ ✦2 ➜  k get po
NAME    READY   STATUS    RESTARTS   AGE
mysql   1/1     Running   0          8m1s

Follow steps on how to configure all key-value pairs in a Secret as container environment variables from K8S docs.

## webapp-pod.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-12-29T17:57:07Z"
  labels:
    name: webapp-pod
name: webapp-pod
namespace: default
resourceVersion: "802"
uid: b134a439-e86d-45d2-af52-717d17717da1
spec:
  containers:
  - image: kodekloud/simple-webapp-mysql
    imagePullPolicy: Always
    name: webapp
    envFrom:
    - secretRef:
        name: db-secret 

controlplane ~ ✦2 ➜  k apply -f webapp-pod.yml 
pod/webapp-pod created

controlplane ~ ✦2 ➜  k get po
NAME         READY   STATUS    RESTARTS   AGE
mysql        1/1     Running   0          13m
webapp-pod   1/1     Running   0          2s 

Identify the name of the containers running in the blue pod.

controlplane ~ ➜  k get po
NAME        READY   STATUS              RESTARTS   AGE
app         1/1     Running             0          36s
blue        0/2     ContainerCreating   0          7s
fluent-ui   1/1     Running             0          37s
red         0/3     ContainerCreating   0          23s 

Answer

controlplane ~ ➜  k describe po blue
Name:             blue
Namespace:        default
Priority:         0
Service Account:  default
Node:             controlplane/192.36.217.6
Start Time:       Fri, 29 Dec 2023 13:12:32 -0500
Labels:           <none>
Annotations:      <none>
Status:           Pending
IP:               
IPs:              <none>
Containers:
teal:
    Container ID:  
    Image:         busybox
    Image ID:      
    Port:          <none>
    Host Port:     <none>
    Command:
    sleep
    4500
    State:          Waiting
    Reason:       ContainerCreating
    Ready:          False
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-vrvfc (ro)
navy:
    Container ID:  
    Image:         busybox
    Image ID:      
    Port:          <none>
    Host Port:     <none>
    Command:
    sleep
    4500
    State:          Waiting
    Reason:       ContainerCreating
    Ready:          False
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-vrvfc (ro) 

Create a multi-container pod with 2 containers. If the pod goes into the crashloopbackoff then add the command sleep 1000 in the lemon container. Use the spec given below:

Name: yellow
Container 1 Name: lemon
Container 1 Image: busybox
Container 2 Name: gold
Container 2 Image: redis

Answer

ontrolplane ~ ➜  k run yellow --image busybox $do
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: yellow
name: yellow
spec:
  containers:
  - image: busybox
    name: yellow
    resources: {}
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}

controlplane ~ ➜  k run yellow --image busybox $do > yellow.yml 

## yellow.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: yellow
name: yellow
spec:
  containers:
  - image: busybox
    name: lemon
    resources: {}
  - image: redis
    name: gold 
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}

controlplane ~ ➜  k apply -f yellow.yml 
pod/yellow created 

controlplane ~ ➜  k get po
NAME        READY   STATUS             RESTARTS     AGE
app         1/1     Running            0            8m39s
blue        2/2     Running            0            7m34s
fluent-ui   1/1     Running            0            8m39s
red         3/3     Running            0            8m26s
yellow      1/2     CrashLoopBackOff   1 (4s ago)   7s

## yellow.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: null
  labels:
    run: yellow
name: yellow
spec:
  containers:
  - image: busybox
    name: lemon
    resources: {}
    command:
    - "sleep"
    - "1000"
  - image: redis
    name: gold   
dnsPolicy: ClusterFirst
restartPolicy: Always
status: {}

controlplane ~ ➜  k delete -f yellow.yml 
pod "yellow" deleted

controlplane ~ ➜  k apply -f yellow.yml 
pod/yellow created

controlplane ~ ➜  k get po
NAME        READY   STATUS    RESTARTS   AGE
app         1/1     Running   0          9m44s
blue        2/2     Running   0          8m39s
fluent-ui   1/1     Running   0          9m44s
red         3/3     Running   0          9m31s
yellow      2/2     Running   0          3s 

controlplane ~ ➜  k describe po yellow 
Name:             yellow
Namespace:        default
Priority:         0
Service Account:  default
Node:             controlplane/192.11.203.9
Start Time:       Sat, 30 Dec 2023 03:10:46 -0500
Labels:           run=yellow
Annotations:      <none>
Status:           Running
IP:               10.244.0.13
IPs:
IP:  10.244.0.13
Containers:
lemon:
    Container ID:  containerd://eba9ba778ac377f05a4061170c3229c0361103ab3dbad6710d28f32a95fc8f77
    Image:         busybox
    Image ID:      docker.io/library/busybox@sha256:ba76950ac9eaa407512c9d859cea48114eeff8a6f12ebaa5d32ce79d4a017dd8
    Port:          <none>
    Host Port:     <none>
    Command:
    sleep
    1000
    State:          Running
    Started:      Sat, 30 Dec 2023 03:10:48 -0500
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-m8gtm (ro)
gold:
    Container ID:   containerd://f0ab41cb48bb10d4006833ecb452800b58974d578a869cfac5e6e7dbe2052029
    Image:          redis
    Image ID:       docker.io/library/redis@sha256:a7cee7c8178ff9b5297cb109e6240f5072cdaaafd775ce6b586c3c704b06458e
    Port:           <none>
    Host Port:      <none>
    State:          Running
    Started:      Sat, 30 Dec 2023 03:10:48 -0500
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-m8gtm (ro)

Inspect the app pod and identify the number of containers in it. It is deployed in the elastic-stack namespace.

Answer

controlplane ~ ➜  k get po -n elastic-stack
NAME             READY   STATUS    RESTARTS   AGE
app              1/1     Running   0          13m
elastic-search   1/1     Running   0          13m
kibana           1/1     Running   0          13m

controlplane ~ ➜  k describe po app
Name:             app
Namespace:        default
Priority:         0
Service Account:  default
Node:             controlplane/192.11.203.9
Start Time:       Sat, 30 Dec 2023 03:01:05 -0500
Labels:           name=app
Annotations:      <none>
Status:           Running
IP:               10.244.0.8
IPs:
IP:  10.244.0.8
Containers:
app:
    Container ID:   containerd://80c1ffb344a3f209d2014335e046bf7eef23c4d319274f047c7b8972ff578694
    Image:          kodekloud/event-simulator
    Image ID:       docker.io/kodekloud/event-simulator@sha256:1e3e9c72136bbc76c96dd98f29c04f298c3ae241c7d44e2bf70bcc209b030bf9
    Port:           <none>
    Host Port:      <none>
    State:          Running
    Started:      Sat, 30 Dec 2023 03:02:20 -0500
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /log from log-volume (rw)
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-s4djx (ro) 

The application in the elastic-stack namespace outputs logs to the file /log/app.log. View the logs and try to identify the user having issues with Login.

controlplane ~ ➜  k get po -n elastic-stack
NAMESPACE       NAME                                   READY   STATUS    RESTARTS   AGE
elastic-stack   app                                    1/1     Running   0          18m
elastic-stack   elastic-search                         1/1     Running   0          18m
elastic-stack   kibana                                 1/1     Running   0          18m

Answer

controlplane ~ ➜  k -n elastic-stack exec -it app -- tail -10 /log/app.log
[2023-12-30 08:18:12,459] INFO in event-simulator: USER3 is viewing page3
[2023-12-30 08:18:12,725] WARNING in event-simulator: USER5 Failed to Login as the account is locked due to MANY FAILED ATTEMPTS.
[2023-12-30 08:18:12,725] INFO in event-simulator: USER4 is viewing page2
[2023-12-30 08:18:13,460] INFO in event-simulator: USER3 is viewing page3
[2023-12-30 08:18:13,726] INFO in event-simulator: USER3 logged in
[2023-12-30 08:18:14,461] WARNING in event-simulator: USER7 Order failed as the item is OUT OF STOCK.
[2023-12-30 08:18:14,461] INFO in event-simulator: USER1 logged in
[2023-12-30 08:18:14,727] INFO in event-simulator: USER4 logged in
[2023-12-30 08:18:15,462] INFO in event-simulator: USER1 logged in
[2023-12-30 08:18:15,729] INFO in event-simulator: USER3 logged in 

Edit the pod to add a sidecar container to send logs to Elastic Search. Mount the log volume to the sidecar container. Only add a new container. Do not modify anything else. Use the spec provided below.

Name: app
Container Name: sidecar
Container Image: kodekloud/filebeat-configured
Volume Mount: log-volume
Mount Path: /var/log/event-simulator/
Existing Container Name: app
Existing Container Image: kodekloud/event-simulator

controlplane ~ ➜  k get po -n elastic-stack
NAMESPACE       NAME                                   READY   STATUS    RESTARTS   AGE
elastic-stack   app                                    1/1     Running   0          18m
elastic-stack   elastic-search                         1/1     Running   0          18m
elastic-stack   kibana                                 1/1     Running   0          18m

Answer

controlplane ~ ➜  k get po app -n elastic-stack -o yaml > elastic-app.yml

Add a sidecar container to the YAML file. Follow K8S docs for steps.

## elastic-app.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-12-30T08:01:04Z"
  labels:
    name: app
name: app
namespace: elastic-stack
resourceVersion: "1071"
uid: ee0727bd-ef91-4817-b717-1582c890cae7
spec:
  containers:
  - image: kodekloud/event-simulator
    imagePullPolicy: Always
    name: app
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /log
      name: log-volume
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-78bvz
      readOnly: true
  - name: sidecar
    image: kodekloud/filebeat-configured
    volumeMounts:
    - name: log-volume
      mountPath: /var/log/event-simulator/  

controlplane ~ ✦ ✖ k delete -f elastic-app.yml  $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "app" force deleted 

controlplane ~ ✦ ✖ vi elastic-app.yml 

controlplane ~ ✦ ➜  k apply -f elastic-app.yml 
pod/app created

controlplane ~ ✦ ➜  k get po -n elastic-stack 
NAME             READY   STATUS    RESTARTS   AGE
app              2/2     Running   0          21s
elastic-search   1/1     Running   0          43m
kibana           1/1     Running   0          43m

What is the image used by the initContainer in the blue pod? What is its state?

controlplane ~ ➜  k get po
NAME    READY   STATUS    RESTARTS   AGE
red     1/1     Running   0          32s
green   2/2     Running   0          32s
blue    1/1     Running   0          32s 

Answer

controlplane ~ ➜  k describe po blue
Name:             blue
Namespace:        default
Priority:         0
Service Account:  default
Node:             controlplane/192.12.137.9
Start Time:       Sat, 30 Dec 2023 08:47:05 +0000
Labels:           <none>
Annotations:      <none>
Status:           Running
IP:               10.42.0.10
IPs:
IP:  10.42.0.10
Init Containers:
init-myservice:
    Container ID:  containerd://a2eb2f74006ea5f3645334bdb11b774f1399e440e53a0a3105717eb260554740
    Image:         busybox
    Image ID:      docker.io/library/busybox@sha256:ba76950ac9eaa407512c9d859cea48114eeff8a6f12ebaa5d32ce79d4a017dd8
    Port:          <none>
    Host Port:     <none>
    Command:
    sh
    -c
    sleep 5
    State:          Terminated
    Reason:       Completed
    Exit Code:    0
    Started:      Sat, 30 Dec 2023 08:47:08 +0000
    Finished:     Sat, 30 Dec 2023 08:47:13 +0000
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
    /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-7djbh (ro)

What is the state of the purple POD?

controlplane ~ ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
red      1/1     Running    0          3m1s
green    2/2     Running    0          3m1s
blue     1/1     Running    0          3m1s
purple   0/1     Init:0/2   0          40s 

Answer

controlplane ~ ➜  k describe po purple | grep -i status
Status:           Pending
Type              Status

Update the pod red to use an initContainer that uses the busybox image and sleeps for 20 seconds

controlplane ~ ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
red      1/1     Running    0          5m27s
green    2/2     Running    0          5m27s
blue     1/1     Running    0          5m27s
purple   0/1     Init:0/2   0          3m6s 

Answer

controlplane ~ ➜  k get po red  -o yaml > red.yml

Add the initContainer in the YAML file. Follow K8s docs for steps.

## red.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-12-30T08:47:05Z"
  name: red
  namespace: default
resourceVersion: "909"
uid: 2a18cd56-4b47-49f5-8a9b-a294020d2773
spec:
  initContainers:
  - name: initcontainer
    image: busybox
    command: ['sh', '-c', 'sleep 20']
  containers:
  - command:
    - sh
    - -c
    - echo The app is running! && sleep 3600
    image: busybox:1.28
    imagePullPolicy: IfNotPresent
    name: red-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-r4zhp
      readOnly: true 

controlplane ~ ✦ ➜  k delete -f red.yml $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "red" force deleted

controlplane ~ ✦ ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
green    2/2     Running    0          10m
blue     1/1     Running    0          10m
purple   0/1     Init:0/2   0          7m53s

controlplane ~ ✦ ➜  k apply -f red.yml 
pod/red created

controlplane ~ ✦ ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
green    2/2     Running    0          10m
blue     1/1     Running    0          10m
purple   0/1     Init:0/2   0          8m2s
red      0/1     Init:0/1   0          2s 

controlplane ~ ✦ ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
green    2/2     Running    0          10m
blue     1/1     Running    0          10m
purple   0/1     Init:0/2   0          8m33s
red      1/1     Running    0          33s

A new application orange is deployed. There is something wrong with it. Identify and fix the issue.

controlplane ~ ✦ ➜  k get po
NAME     READY   STATUS       RESTARTS     AGE
green    2/2     Running      0            11m
blue     1/1     Running      0            11m
purple   0/1     Init:0/2     0            9m31s
red      1/1     Running      0            91s
orange   0/1     Init:Error   1 (6s ago)   7s 

Answer

controlplane ~ ✦2 ➜  k logs orange 
Defaulted container "orange-container" out of: orange-container, init-myservice (init)
Error from server (BadRequest): container "orange-container" in pod "orange" is waiting to start: PodInitializing

controlplane ~ ✦2 ➜ k get po orange -o yaml > orange.yml

Inspect the YAML file. We can see that the command is wrong.

## orange.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-12-30T08:58:50Z"
  name: orange
  namespace: default
resourceVersion: "1228"
uid: 79f7f539-c1e2-4f74-9ebe-cb6065cc49d2
spec:
  containers:
  - command:
    - sh
    - -c
    - echo The app is running! && sleep 3600
    image: busybox:1.28
    imagePullPolicy: IfNotPresent
    name: orange-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-9d8th
      readOnly: true
  dnsPolicy: ClusterFirst
  enableServiceLinks: true
  initContainers:
  - command:
    - sh
    - -c
    - sleeeep 2;
    image: busybox
    imagePullPolicy: Always
    name: init-myservice
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-9d8th
      readOnly: true 

Fix the command in initcontainer.

## orange.yml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2023-12-30T08:58:50Z"
  name: orange
  namespace: default
resourceVersion: "1228"
uid: 79f7f539-c1e2-4f74-9ebe-cb6065cc49d2
spec:
  containers:
  - command:
    - sh
    - -c
    - echo The app is running! && sleep 3600
    image: busybox:1.28
    imagePullPolicy: IfNotPresent
    name: orange-container
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-9d8th
      readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
  initContainers:
  - command:
    - sh
    - -c
    - sleep 2;
    image: busybox
    imagePullPolicy: Always
    name: init-myservice
    resources: {}
    terminationMessagePath: /dev/termination-log
    terminationMessagePolicy: File
    volumeMounts:
    - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
      name: kube-api-access-9d8th
      readOnly: true 

controlplane ~ ✦2 ➜  k delete -f orange.yml $now
Warning: Immediate deletion does not wait for confirmation that the running resource has been terminated. The resource may continue to run on the cluster indefinitely.
pod "orange" force deleted

controlplane ~ ✦2 ➜  k apply -f orange.yml 
pod/orange created

controlplane ~ ✦2 ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
green    2/2     Running    0          20m
blue     1/1     Running    0          20m
red      1/1     Running    0          10m
purple   0/1     Init:1/2   0          18m
orange   0/1     Init:0/1   0          2s

controlplane ~ ✦2 ➜  k get po
NAME     READY   STATUS     RESTARTS   AGE
green    2/2     Running    0          20m
blue     1/1     Running    0          20m
red      1/1     Running    0          10m
purple   0/1     Init:1/2   0          18m
orange   1/1     Running    0          5s 

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