In this lab we will run our first, very basic, application on Kubernetes. We will basically run a single pod as our application.
Create a namespace for this lab:
kubectl create ns lab-04
---
namespace/lab-04 created
Verify that your namespace was created:
kubectl get namespaces
---
NAME STATUS AGE
default Active 44h
kube-system Active 44h
kube-public Active 44h
kube-node-lease Active 44h
lab-04 Active 16s
To run your first pod (the official nginx Docker image), run the following command:
kubectl run --restart=Never --image=nginx nginx -n lab-04
---
pod/nginx created
The above command will create a single pod that is based on the official nginx
Docker image in the lab-04 namespace. Run the following command to verify that the pod has been
created and is in the running state (if the pod is not yet in the running state
wait a couple of seconds and try to run the command again):
kubectl get pods -n lab-04
---
NAME READY STATUS RESTARTS AGE
nginx 1/1 Running 0 40s
As we have not yet configured any services and/or ingresses we will use a litte "hack" to access our pod we just created.
Run the following command to forward the port of the pod (in our case port 80) running in our Kubernetes cluster to a port on your laptop (in this case port 8080).
kubectl port-forward pod/nginx 8080:80 -n lab-04
---
Forwarding from 127.0.0.1:8080 -> 80
Forwarding from [::1]:8080 -> 80
NOTE: your prompt will be locked by the port-forward process
Now go to your browser and surf to http://localhost:8080, you should be greeted with the default nginx welcome page:
If that works you can close the port-foward connection by pressing CTRL+c and you will get access to your prompt again.
To connect to your pod, you can use the following command (notice how it
resembles the docker exec command in options and functionality):
kubectl exec -ti nginx -n lab-04 -- bash
---
root@nginx:/#
Notice how the prompt changes. exec-ing into a pod is very powerful for
troubleshooting, but keep in mind that by default pods/containers are immutable
so remember to not make any changes inside the pods/container.
To exit run the exit command.
root@nginx:/# exit
---
exit
Again similar to when working with Docker containers, Kubernetes has a built-in feature that exposes all stdout/stderr output into logs. To access those logs issue the following command:
kubectl logs nginx -n lab-04
---
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2022/02/24 07:04:14 [notice] 1#1: using the "epoll" event method
2022/02/24 07:04:14 [notice] 1#1: nginx/1.21.6
2022/02/24 07:04:14 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6)
2022/02/24 07:04:14 [notice] 1#1: OS: Linux 5.10.93-0-virt
2022/02/24 07:04:14 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2022/02/24 07:04:14 [notice] 1#1: start worker processes
2022/02/24 07:04:14 [notice] 1#1: start worker process 32
2022/02/24 07:04:14 [notice] 1#1: start worker process 33
127.0.0.1 - - [24/Feb/2022:07:07:34 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:34 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:34 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:35 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:36 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
127.0.0.1 - - [24/Feb/2022:07:07:36 +0000] "GET / HTTP/1.1" 304 0 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.109 Safari/537.36" "-"
NOTE: if your logs are empty, repeat Task 2 where you
kubectl port-forwardthe container port and hit reload the page a couple more times in your browser
A very handy option of kubectl logs is that you can follow them real-time using the -f
option, this is extremely useful when troubleshooting:
kubectl logs nginx -n lab-04 -f
Hit CTRL+c to exit the logs.
Like with most objects in Kubernetes you can use the kubectl describe command
to get more information about a specific pod, for example:
kubectl describe pods nginx -n lab-04
---
Name: nginx
Namespace: lab-04
Priority: 0
Node: lima-rancher-desktop/172.20.10.3
Start Time: Thu, 24 Feb 2022 08:04:11 +0100
Labels: run=nginx
Annotations: <none>
Status: Running
IP: 10.42.0.20
IPs:
IP: 10.42.0.20
Containers:
nginx:
Container ID: docker://f9df9679d14927fb59bb6047b9c0134e3cfa2574567af0808c02f565b8ad6a44
Image: nginx
Image ID: docker-pullable://nginx@sha256:2834dc507516af02784808c5f48b7cbe38b8ed5d0f4837f16e78d00deb7e7767
Port: <none>
Host Port: <none>
State: Running
Started: Thu, 24 Feb 2022 08:04:14 +0100
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-csg5v (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
kube-api-access-csg5v:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 5m8s default-scheduler Successfully assigned lab-04/nginx to lima-rancher-desktop
Normal Pulling 5m7s kubelet Pulling image "nginx"
Normal Pulled 5m6s kubelet Successfully pulled image "nginx" in 1.75104581s
Normal Created 5m5s kubelet Created container nginx
Normal Started 5m5s kubelet Started container nginx
Clean up the namespace for this lab:
kubectl delete ns lab-04
---
namespace "lab-04" deleted