minikube: how to add second container to the pod? - kubernetes

Question

I am looking for help on how to add a second container to the existing pod (i mean one pod with two containers). The error is CrashLoopBackOff. I am using minikube. I request any assistance in resolving the issue will be appreciated.
wordpress.yaml
--------XXXX------------------
apiVersion: v1
kind: Service
metadata:
name: my-nginx-svc
labels:
app: nginx
spec:
type: LoadBalancer
ports:
- port: 80
selector:
app: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-nginx
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
- name: wordpress
image: wordpress
ports:
- containerPort: 80
#watch kubectl get pods
Every 2.0s: kubectl get pods cent8-minikube: Wed Jun 10 16:47:30 2020
NAME READY STATUS RESTARTS AGE
my-nginx-6b474476c4-9p4cn 1/1 Running 0 5h41m
my-nginx-6b474476c4-m2xkd 1/1 Running 0 5h41m
my-nginx-9f44b5996-744n5 1/2 CrashLoopBackOff 9 21m
my-nginx-9f44b5996-vl6g2 1/2 CrashLoopBackOff 9 22m
test-minikube-f4df69575-2sbl5 1/1 Running 0 26h
[root#cent8-minikube ~]# kubectl describe pod my-nginx-9f44b5996-vl6g2
Name: my-nginx-9f44b5996-vl6g2
Namespace: default
Priority: 0
Node: cent8-minikube/192.168.194.128
Start Time: Wed, 10 Jun 2020 16:25:14 -0700
Labels: app=nginx
pod-template-hash=9f44b5996
Annotations: <none>
Status: Running
IP: 172.17.0.8
IPs:
IP: 172.17.0.8
Controlled By: ReplicaSet/my-nginx-9f44b5996
Containers:
nginx:
Container ID: docker://5e4cfd4e726373916a105a95644a7a286966482e33eaaac986e44514aef86606
Image: nginx:1.14.2
Image ID: docker-pullable://nginx#sha256:f7988fb6c02e0ce69257d9bd9cf37ae20a60f1df7563c3a2a6abe24160306b8d
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Wed, 10 Jun 2020 16:25:16 -0700
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-lqnj8 (ro)
wordpress:
Container ID: docker://5e37277badca1658a10d4d826428f538a45d5e0eaecabd5e196f8b6ab5848ec7
Image: wordpress
Image ID: docker-pullable://wordpress#sha256:ff8be61894e74b6a005ab54ba73aa7084b6dbd11605f12ac383549763918bf09
Port: 80/TCP
Host Port: 0/TCP
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Error
Exit Code: 1
Started: Wed, 10 Jun 2020 16:46:37 -0700
Finished: Wed, 10 Jun 2020 16:46:38 -0700
Ready: False
Restart Count: 9
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-lqnj8 (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-lqnj8:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-lqnj8
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 23m default-scheduler Successfully assigned default/my-nginx-9f44b5996-vl6g2 to cent8-minikube
Normal Pulled 23m kubelet, cent8-minikube Container image "nginx:1.14.2" already present on machine
Normal Created 23m kubelet, cent8-minikube Created container nginx
Normal Started 23m kubelet, cent8-minikube Started container nginx
Normal Pulling 22m (x4 over 23m) kubelet, cent8-minikube Pulling image "wordpress"
Normal Pulled 22m (x4 over 23m) kubelet, cent8-minikube Successfully pulled image "wordpress"
Normal Created 22m (x4 over 23m) kubelet, cent8-minikube Created container wordpress
Normal Started 22m (x4 over 23m) kubelet, cent8-minikube Started container wordpress
Warning BackOff 3m35s (x95 over 23m) kubelet, cent8-minikube Back-off restarting failed container
[root#cent8-minikube ~]#
[root#cent8-minikube ~]# kubectl describe pod my-nginx-9f44b5996-744n5
Name: my-nginx-9f44b5996-744n5
Namespace: default
Priority: 0
Node: cent8-minikube/192.168.194.128
Start Time: Wed, 10 Jun 2020 16:25:33 -0700
Labels: app=nginx
pod-template-hash=9f44b5996
Annotations: <none>
Status: Running
IP: 172.17.0.10
IPs:
IP: 172.17.0.10
Controlled By: ReplicaSet/my-nginx-9f44b5996
Containers:
nginx:
Container ID: docker://9e3d6f0073e51eb475c2f2677fa413509f49a07c955d04b09417811d37ba8433
Image: nginx:1.14.2
Image ID: docker-pullable://nginx#sha256:f7988fb6c02e0ce69257d9bd9cf37ae20a60f1df7563c3a2a6abe24160306b8d
Port: 80/TCP
Host Port: 0/TCP
State: Running
Started: Wed, 10 Jun 2020 16:25:35 -0700
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-lqnj8 (ro)
wordpress:
Container ID: docker://2ca8f22ab14b88973dca8d4d486f82a5b0d9bc7b84960882cff0a81afd744bf4
Image: wordpress
Image ID: docker-pullable://wordpress#sha256:ff8be61894e74b6a005ab54ba73aa7084b6dbd11605f12ac383549763918bf09
Port: 80/TCP
Host Port: 0/TCP
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Error
Exit Code: 1
Started: Wed, 10 Jun 2020 16:46:41 -0700
Finished: Wed, 10 Jun 2020 16:46:42 -0700
Ready: False
Restart Count: 9
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from default-token-lqnj8 (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
default-token-lqnj8:
Type: Secret (a volume populated by a Secret)
SecretName: default-token-lqnj8
Optional: false
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s
node.kubernetes.io/unreachable:NoExecute for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 26m default-scheduler Successfully assigned default/my-nginx-9f44b5996-744n5 to cent8-minikube
Normal Pulled 26m kubelet, cent8-minikube Container image "nginx:1.14.2" already present on machine
Normal Created 26m kubelet, cent8-minikube Created container nginx
Normal Started 26m kubelet, cent8-minikube Started container nginx
Normal Pulling 25m (x4 over 26m) kubelet, cent8-minikube Pulling image "wordpress"
Normal Pulled 25m (x4 over 26m) kubelet, cent8-minikube Successfully pulled image "wordpress"
Normal Created 25m (x4 over 26m) kubelet, cent8-minikube Created container wordpress
Normal Started 25m (x4 over 26m) kubelet, cent8-minikube Started container wordpress
Warning BackOff 67s (x116 over 26m) kubelet, cent8-minikube Back-off restarting failed container
[root#cent8-minikube ~]#
``` [root#cent8-minikube ~]# kubectl logs my-nginx-9f44b5996-vl6g2 -c wordpress WordPress not found in /var/www/html - copying now... Complete! WordPress has been successfully copied to /var/www/html AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.8. Set the 'ServerName' directive globally to suppress this message (98)Address already in use: AH00072: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down AH00015: Unable to open logs
How to add a second container to the pod?
where to check the logs of the crash container or How to debug?
could you guide me, how to fix this error?

Answer 1

To check logs of a container in a pod
kubectl logs my-pod -c my-container
To check logs of previous instance of a container in a pod
kubectl logs my-pod -c my-container --previous
In your case this will translate to
kubectl logs my-nginx-9f44b5996-vl6g2 -c nginx
kubectl logs my-nginx-9f44b5996-vl6g2 -c wordpress
Wordpress is probably not a good idea to run with nginx in the same pod. Check this guide on multicontainer pod
Check this guide to run wordpress on kubernetes

Answer 2

The important part of your error is this:
Address already in use: AH00072: make_sock: could not bind to address 0.0.0.0:80 no listening sockets available, shutting down
If you run multiple containers in a single pod, they share a network namespace. Where the Service forwards to port 80 of the pod, it could reach any container. In this example, that means you can't have two containers in the same pod listening to the same port.
A better practice would be to split these two components into two separate Deployments, each with a matching Service. To do this:
Make two copies of your existing Deployment. In one, delete all mentions of Wordpress. In the other, delete the Nginx container and otherwise globally replace nginx with wordpress.
Make two copies of your existing Service. Change the second one to be type: ClusterIP, and globally replace nginx with wordpress.
In your Nginx proxy configuration, where you proxy_pass to the Wordpress container, change its backend to http://my-wordpress-svc/.
It would be very routine to wind up with 5 separate YAML files for this (two Deployments, two Services, one ConfigMap) and you can run kubectl apply -f on a directory to install them all in one shot.

Answer 3

While I agree that running separate applications in separate Pods, sometimes it's easier to keep them together. In the current scenario this could have been achieved as follows:
Wordpress is hard configure, so moving Nginx to a separate port is more feasible (if not totally straight forward)
apiVersion: v1
kind: ConfigMap
metadata:
name: nginx
data:
default.conf.template: |
server {
listen ${NGINX_PORT};
server_name localhost;
location / {
root /usr/share/nginx/html;
index index.html index.htm;
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
root /usr/share/nginx/html;
}
}
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-nginx
labels:
app: nginx
spec:
replicas: 3
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx
env:
- name: NGINX_PORT
value: "81"
volumeMounts:
- mountPath: /etc/nginx/templates/
name: config
ports:
- containerPort: 81
- name: wordpress
image: wordpress
ports:
- containerPort: 80
volumes:
- name: config
configMap:
name: nginx