Scheduling Flashcards
True or false?
Kubernetes adds a name in the nodeName section automatically in the spec defined when creatin the yaml file in a declarative way.
True
True or false?
Kubernetes won’t allow you to change the nodeName after a pod has been created
True. the nodeName has to be set upon pod creation. It cannot be modified afterwards. In that case you would have to use a binding object.
Lets say I have a pod and there’s no scheduler present, since I cannot assign a the pod to a node after the pod has been created, I would have to first delete the pod and afterwards, use the yaml file to create the pod again with the nodeName flag included, what single command can i use ton achieve these two steps?
kubectl replace –force -f your_yaml_filename.yaml
The command generally used to check the status of a pod is kubectl get po, however, what if I don’t want to run this same command over and over again to check the status of it?
kubectl get po –watch
What command can I use to check the node in which the port is running?
kubectl get po -o wide
_______are key/value pairs that are attached to objects such as Pods.
Labels
Via a label ___________, the client/user can identify a set of objects. The label _________is the core grouping primitive in Kubernetes.
selector
how can I use a selector in Kubernetes?
kubectl get pods –selector app=App1
what command can I use to get the number of pods?
kubectl get pods –no-headers| wc -l
command to list all objects in a namespace:
kubectl get all –no-headers | wc-l
true or false:
taints are placed on nodes and tolerations are places on pods.
True
What are the main taint effects?
No schedule, PreferNoSchedule, NoExecute
The _______ node has all the capability of hosting pods and running all management software. The ________ does not schedule pods on the master node.
master node
Scheduler (upon cluster setup, a taint is setup on the master node automatically that prevents any pods to be scheduled on the master node).
What command can I use to see the master node taint created automatically?
kubectl describe node kubemaster | grep Taint
How to label a node imperatively?
kubectl label nodes <node-name> <label-key>=<label-value></label-value></label-key></node-name>
Whats is the objective of node affinity?
Is to ensure that pods are hosted on particular nodes.
What is node selector?
is a simple way to specify which nodes a pod should be scheduled onto based on a set of label key-value pairs.
Node _________is limited to looking for exact label key-value pair matches, meaning that it cannot use logical operators or more complex matching rules.
Selector
Node __________ enables a conditional approach with logical operators in the matching process.
affinity
Node Affinity uses a combination of label selectors, operators, and values to match nodes. The operators include:
- In
- NotIn
- Exists
- DoesNotExist
Whats are the node affinity types - in available?
requiredDuringSchedulingIgnoredDuringExecution
preferredDuringSchedulingIgnoredDuringExecution
What does preferredDuringSchedulingIgnoredDuringExecution mean?
- The scheduler will attempt to schedule the pod on a node that matches one of the rules.
- If no nodes match any of the rules, the pod may be scheduled on any node.
What does requiredDuringSchedulingIgnoredDuringExecutionmean?
- Ensure that the pod is only scheduled on nodes that match the specified node selector rules.
- If no nodes match the node selector rules, the pod remains unscheduled.
What is the planned node afiinity type?
requiredDuringSchedulingRequiredDuringExecution
Node affnity support the following operators:
In
NotIn
Exists
DoesNotExist
Gt
Lt
What is the LimitRange in Kubernetes?
How does Kubernetes define “Limits”?
the maximum amount of a resource to be used by a container.
__________ are the minimum guaranteed amount of a resource that is reserved for a container.
Requests
_______ is a compressible resource, meaning that it can be stretched in order to satisfy all the demand. In case that the processes request too much ______, some of them will be throttled.
CPU
_________ is a non-compressible resource, meaning that it can’t be stretched in the same manner as CPU. If a process doesn’t get enough __________ to work, the process is killed.
Memory
A _____________(and their analogues Kibibyte, Gibibyte,…) is 2 to the power of 20 bytes. It was created to avoid the confusion with the Kilo, Mega definitions of the metric system. You should be using this notation, as it’s the canonical definition for bytes, while Kilo and Mega are multiples of 1000. the _________________ is multiple of 1024.
Mebibyte
True or false: The status OOMKilled indicates that it is failing because the pod ran out of memory. Identify the memory limit set on the POD.
true
What does a DaemonSet in Kubernetes do?
ensures that all (or some) Nodes run a copy of a Pod. As nodes are added to the cluster, Pods are added to them. As nodes are removed from the cluster, those Pods are garbage collected. Deleting a DaemonSet will clean up the Pods it created
True or false: you can create static pods by placing their definition files in the designated directory.
True (this only applies to pods as the kubelet can only interpret pods)
____________ are a way to run pods directly through a Kubernetes node’s kubelet daemon instead of through the API server.
Static Pods. This allows static pods to start up even if the API server is not running yet, which is useful for bootstrapping the Kubernetes control plane components like the API server, controller manager, and scheduler.
True or false: regular API-server created pods do not have acces to the kubelet filesystem.
True, this is why Static pods can also be useful for running privileged pods that need access to the kubelet filesystem.
Why are static pods in kubernetes marked as controlplane?
Static pods in Kubernetes are marked as “controlplane” because they are typically used to run the Kubernetes control plane components (like the API server and controller-manager) directly on a node, managed by the kubelet rather than the API server, which is the primary way pods are managed.
