If you are not familiar with the oc command, refer to OpenShift - Getting Started with the oc command.

• LimitRange can be used to set the default amount of CPU/memory/ephemeral-storage as well as the minimum and maximum amount of CPU/memory/ephemeral-storage for all containers or pods in a namespace

You can set both requests and limits.

• requests
  • ​the amount of memory / CPU / ephemeral-storage that is reserved for containers / pods. For example, if a node has 10 GB of memory and a pod requests 1 GB of memory, then 1 of the 10 GB of memory on the node would be reserved for the pod, meaning the node would then have 9 remaining GB of memory for other containers / pods. This is why it's important that containers / pods only request the minimum amount of CPU / memory that the container / pod require.
• limit
  • ​the maximum amount of memory / CPU / ephemeral-storage a container or pod can use
  • if a container or pod reaches the CPU limit, the container or pod will be throttled (won’t let it consume any more CPU)
  • if a container or pod reaches the memory limit, Out Of Memory (OOM) should occur and the pod should be killed
  • if a container or pod reaches the storage limit, the pod should be evicted

Before configuring Requests and Limits for CPU and memory, you will probably want to

• determine the average amount of CPU and memory being used by pods
• determine the amount of CPU and memory available on your nodes

Check out my article FreeKB - OpenShift - CPU and memory usage.

Before updating a resource such as a deployment to have requests/limits, you may want to first issue the oc get limits command to determine if there is a LimitRange resource in the namespace.

~]$ oc get limits
NAME                       CREATED AT
my-namespace-limits        2025-03-13T03:05:10Z

If there is a LimitRange resource in the namespace, the oc describe command can be used to display the configuration of the LimitRange resource in the namespace.

~]$ oc describe limits my-namespace-limits
Name:       my-namespace-limits
Namespace:  my-project
Type        Resource           Min  Max  Default Request  Default Limit  Max Limit/Request Ratio
----        --------           ---  ---  ---------------  -------------  -----------------------
Container   cpu                1m   1    5m               300m           -
Container   memory             4Mi  2Gi  16Mi             256Mi          -
Container   ephemeral-storage  -    -    1Mi              1Gi            -
Pod         ephemeral-storage  -    3Gi  -                -              -

If there is a LimitRange resource in the namespace, and if the resource managing the pod (such as a deployment) does not have requests/limits, then the pods in the namespace will have the values defined in the LimitRange resource. In this example, since the LimitRange sets cpu, memory and ephemeral-storage requests and limits for containers, each container in the pod should have the cpu, memory and ephemeral-storage requests and limits defined in the LimitRange resource in the namespace.

~]$ oc get pod/my-deployment-5b544f4785-hxkp4 --output yaml
spec:
  containers:
  - resources:
      limits:
        cpu: 300m
        ephemeral-storage: 1Gi
        memory: 256Mi
      requests:
        cpu: 5m
        ephemeral-storage: 1Mi
        memory: 16Mi

Setting the requests/limits in a pod or deployment will take precedence over the requests/limits in the LimitRange resource.

The oc set resources command can be used to update a deployment or deployment config to have certain requests / limits. This will update the deployment or pod YAML to have the requests / limits.

AVOID TROUBLE

This will set the CPU and memory requests / limits for a single deployment / container / pod in the project. If you want to set the combined CPU and memory limits of all of the containers or pods in a namespace, refer to Create CPU Memory Limits using a YAML template file.

~]$ oc set resources deployment my-deployment --limits=cpu=200m,memory=512Mi --requests=cpu=100m,memory=256Mi
deployment.apps/my-deployment resource requirements updated

Or you can edit the deployment, deployment config, replica set, replication controller, stateful set, or pod YAML with requests / limits.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-openshift
spec:
  replicas: 1
  selector:
    matchLabels:
      app: hello-openshift
  template:
    metadata:
      labels:
        app: hello-openshift
    spec:
      containers:
      - name: hello-openshift
        image: openshift/hello-openshift:latest
        ports:
        - containerPort: 80
        resources:
          requests:
            cpu: 10m
            memory: 128Mi
          limits:
            cpu: 500m
            memory: 512Mi

The oc apply or oc create command with the -f or --filename option can be used to create the deployment using the template JSON or YAML file.

The oc replace command can be used to replace a deployment using a new or updated template JSON or YAML file.

The oc edit command can be used to update a deployments template YAML file.

~]$ oc create --filename deployment.yml
deployment.apps/hello-openshift created

The oc get deployments command can be used to list the deployments.

~]# oc get deployments
NAME                DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
hello-openshift     1         1         1            1           23s

The oc get pods command can be used to determine if the pod is up and running.

~]$ oc get pods
NAME                READY   STATUS      RESTARTS   AGE
hello-openshift     1/1     Running     0          23s

The oc describe deployment or oc describe pod command can be used to validate that the deployment or pod has CPU and memory limits.

~]$ oc describe deployment my-deployment
Pod Template:
  Containers:
   my-container:
    Limits:
      cpu:     200m
      memory:  512Mi
    Requests:
      cpu:        100m
      memory:     256Mi