Kubernetes has quickly grown to become one of the most popular container orchestration frameworks in the industry. Kubernetes has many benefits and it known for its flexibility and ease of use. With its growing community, many tools and technologies have been developed to make it simple to use.
<terminal inline>kubectl<terminal inline> is one of the most popular open-source CLIs for interacting with a Kubernetes cluster. In this guide, you will learn about <terminal inline>describe<terminal inline>, one of its popular commands.
What is kubectl describe Used For?
As is evident by its name, the <terminal inline>kubectl describe<terminal inline> command is used to view details of a Kubernetes resource or resource group. Here's how it's used:
kubectl describe <resource-type> <resource-name-prefix>
Common resource types include pods, services, nodes, events, and more. The command takes the prefix of the resource name as input. You can also provide the complete name of the resource and it would work just fine.
Here's how you can use this command:
kubectl describe deployment test-webapp
Here's what the output would look like:
Name: test-webapp
Namespace: default
CreationTimestamp: Tue, 31 May 2022 10:38:00 +0530
Labels: <none>
Annotations: deployment.kubernetes.io/revision: 1
Selector: run=test-webapp
Replicas: 1 desired | 1 updated | 1 total | 1 available | 0 unavailable
StrategyType: RollingUpdate
MinReadySeconds: 0
RollingUpdateStrategy: 25% max unavailable, 25% max surge
Pod Template:
Labels: run=test-webapp
Containers:
test-webapp:
Image: k8s.gcr.io/hpa-example
Port: 80/TCP
Host Port: 0/TCP
Limits:
cpu: 25m
memory: 10Mi
Requests:
cpu: 10m
memory: 5Mi
Environment: <none>
Mounts: <none>
Volumes: <none>
Conditions:
Type Status Reason
---- ------ ------
Progressing True NewReplicaSetAvailable
Available True MinimumReplicasAvailable
OldReplicaSets: <none>
NewReplicaSet: test-webapp-d5f9b9d8d (1/1 replicas created)
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal ScalingReplicaSet 6d8h deployment-controller Scaled up replica set test-webapp-d5f9b9d8d to 1
Exploring kubectl describe in Detail
The <terminal inline>kubectl describe<terminal inline> command provides a few options to tailor it to your liking. Here are some of those:
Viewing by label
You can also use metadata labels to filter and identify resources when describing them. Here's what the syntax looks like for that:
Viewing resources using a file
The <terminal inline>kubectl describe<terminal inline> command allows you to query for resources using data stored in a file. Here's what the syntax looks like:
kubectl describe -f test-pod.json
Shorthand syntax
You can use the following syntax too:
kubectl describe <resource-type>/<resource-name>
It works the same as the syntax shared at the beginning of the article.
kubectl describe vs kubectl get
People often debate on whether or not <terminal inline>describe<terminal inline> was needed when there already was a <terminal inline>get<terminal inline> command. To understand this better, let's try to view them side by side:
Here's what a <terminal inline>get<terminal inline> command on a pod returns:
~> kubectl get pod test-webapp-d5f9b9d8d-flqjk
| test-webapp-d5f9b9d8d-flqjk |
1/1 |
Running |
0 |
5m22s |
Here's what a <terminal inline>describe<terminal inline> call on the same pod returns:
$ kubectl describe pod test-webapp-d5f9b9d8d-flqjk
Name: test-webapp-d5f9b9d8d-flqjk
Namespace: default
Priority: 0
Node: minikube/192.168.49.2
Start Time: Mon, 06 Jun 2022 18:00:04 +0530
Labels: pod-template-hash=d5f9b9d8d
run=test-webapp
Annotations: <none>
Status: Running
IP: 10.244.0.16
IPs:
IP: 10.244.0.16
Controlled By: ReplicaSet/test-webapp-d5f9b9d8d
Containers:
test-webapp:
Container ID: docker://d581e3e779ae164630de23594b0c4df8c1eecacdbd6b0b7e68655656d37c7491
Image: k8s.gcr.io/hpa-example
Image ID: docker-pullable://k8s.gcr.io/hpa-example@sha256:581697a37f0e136db86d6b30392f0db40ce99c8248a7044c770012f4e8491544
Port: 80/TCP
Host Port: 0/TCP
State: Waiting
Reason: CrashLoopBackOff
Last State: Terminated
Reason: Error
Exit Code: 137
Started: Mon, 06 Jun 2022 18:38:02 +0530
Finished: Mon, 06 Jun 2022 18:39:07 +0530
Ready: False
Restart Count: 8
Limits:
cpu: 25m
memory: 10Mi
Requests:
cpu: 10m
memory: 5Mi
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-nnjsx (ro)
Conditions:
Type Status
Initialized True
Ready False
ContainersReady False
PodScheduled True
Volumes:
kube-api-access-nnjsx:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: Burstable
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 42m default-scheduler Successfully assigned default/test-webapp-d5f9b9d8d-flqjk to minikube
Normal Pulled 41m kubelet Successfully pulled image "k8s.gcr.io/hpa-example" in 1m0.625635569s
Normal Pulled 30m kubelet Successfully pulled image "k8s.gcr.io/hpa-example" in 1.177994667s
Normal Pulled 29m kubelet Successfully pulled image "k8s.gcr.io/hpa-example" in 1.104291834s
Normal Pulled 28m kubelet Successfully pulled image "k8s.gcr.io/hpa-example" in 1.010987459s
Normal Pulling 26m (x5 over 42m) kubelet Pulling image "k8s.gcr.io/hpa-example"
Normal Created 26m (x5 over 41m) kubelet Created container test-webapp
Normal Pulled 26m kubelet Successfully pulled image "k8s.gcr.io/hpa-example" in 1.132110626s
Normal Started 26m (x5 over 41m) kubelet Started container test-webapp
Warning BackOff 2m21s (x80 over 29m) kubelet Back-off restarting failed container
As you can see, the get command (by default) returns a very quick summary of the status of the resource in question. On the other hand, the describe command prepares a detailed summary of the resource with additional details like container ID, limits, node details, etc.
Also, the <terminal inline>get<terminal inline> command returns the information in a tabular fashion by default. You also have the option to view the information in any other format such as JSON or YAML by passing it as an option. But, the output returned in such a case is quite verbose and is usually difficult to read.
At the end of the day, <terminal inline>describe<terminal inline> provides you with just the right amount of information about your K8s resource. If you are looking for anything less or more, you should look towards <terminal inline>get<terminal inline>.
Final Thoughts
K8s is one of the popular container-orchestration technologies in use right now. The <terminal inline>kubectl describe<terminal inline> command enables developers to look into the current state of their Kubernetes resources. In this guide, we showed you how to use this command as well as contrasted it with another popular command that does a similar job.
