Question: What is About CoreDNS?

Answer: C o r e D N S   i s   a   f l e x i b l e ,   e x t e n s i b l e   D N S   s e r v e r   t h a t   c a n   s e r v e   a s   t h e   K u b e r n e t e s   c l u s t e r   D N S .   L i k e   K u b e r n e t e s ,   t h e   C o r e D N S   p r o j e c t   i s   h o s t e d   b y   t h e   C N C F .   Y o u   c a n   u s e   C o r e D N S   i n s t e a d   o f   k u b e - d n s   i n   y o u r   c l u s t e r   b y   r e p l a c i n g   k u b e - d n s   i n   a n   e x i s t i n g   d e p l o y m e n t ,   o r   b y   u s i n g   t o o l s   l i k e   k u b e a d m   t h a t   w i l l   d e p l o y   a n d   u p g r a d e   t h e   c l u s t e r   f o r   y o u .


Question: What is Installing CoreDNS?

Answer: F o r   m a n u a l   d e p l o y m e n t   o r   r e p l a c e m e n t   o f   k u b e - d n s ,   s e e   t h e   d o c u m e n t a t i o n   a t   t h e   C o r e D N S   w e b s i t e .


Question: What is Upgrading an existing cluster with kubeadm?

Answer: I n   K u b e r n e t e s   v e r s i o n   1 . 2 1 ,   k u b e a d m   r e m o v e d   i t s   s u p p o r t   f o r   k u b e - d n s   a s   a   D N S   a p p l i c a t i o n .   F o r   k u b e a d m   v 1 . 3 4 ,   t h e   o n l y   s u p p o r t e d   c l u s t e r   D N S   a p p l i c a t i o n   i s   C o r e D N S .   Y o u   c a n   m o v e   t o   C o r e D N S   w h e n   y o u   u s e   k u b e a d m   t o   u p g r a d e   a   c l u s t e r   t h a t   i s   u s i n g   k u b e - d n s .   I n   t h i s   c a s e ,   k u b e a d m   g e n e r a t e s   t h e   C o r e D N S   c o n f i g u r a t i o n   ( " C o r e f i l e " )   b a s e d   u p o n   t h e   k u b e - d n s   C o n f i g M a p ,   p r e s e r v i n g   c o n f i g u r a t i o n s   f o r   s t u b   d o m a i n s ,   a n d   u p s t r e a m   n a m e   s e r v e r .


Question: What is Upgrading CoreDNS?

Answer: Y o u   c a n   c h e c k   t h e   v e r s i o n   o f   C o r e D N S   t h a t   k u b e a d m   i n s t a l l s   f o r   e a c h   v e r s i o n   o f   K u b e r n e t e s   i n   t h e   p a g e   C o r e D N S   v e r s i o n   i n   K u b e r n e t e s .   C o r e D N S   c a n   b e   u p g r a d e d   m a n u a l l y   i n   c a s e   y o u   w a n t   t o   o n l y   u p g r a d e   C o r e D N S   o r   u s e   y o u r   o w n   c u s t o m   i m a g e .   T h e r e   i s   a   h e l p f u l   g u i d e l i n e   a n d   w a l k t h r o u g h   a v a i l a b l e   t o   e n s u r e   a   s m o o t h   u p g r a d e .   M a k e   s u r e   t h e   e x i s t i n g   C o r e D N S   c o n f i g u r a t i o n   ( " C o r e f i l e " )   i s   r e t a i n e d   w h e n   u p g r a d i n g   y o u r   c l u s t e r .   I f   y o u   a r e   u p g r a d i n g   y o u r   c l u s t e r   u s i n g   t h e   k u b e a d m   t o o l ,   k u b e a d m   c a n   t a k e   c a r e   o f   r e t a i n i n g   t h e   e x i s t i n g   C o r e D N S   c o n f i g u r a t i o n   a u t o m a t i c a l l y .


Question: What is Tuning CoreDNS?

Answer: W h e n   r e s o u r c e   u t i l i s a t i o n   i s   a   c o n c e r n ,   i t   m a y   b e   u s e f u l   t o   t u n e   t h e   c o n f i g u r a t i o n   o f   C o r e D N S .   F o r   m o r e   d e t a i l s ,   c h e c k   o u t   t h e   d o c u m e n t a t i o n   o n   s c a l i n g   C o r e D N S .


Question: What is What's next?

Answer: Y o u   c a n   c o n f i g u r e   C o r e D N S   t o   s u p p o r t   m a n y   m o r e   u s e   c a s e s   t h a n   k u b e - d n s   d o e s   b y   m o d i f y i n g   t h e   C o r e D N S   c o n f i g u r a t i o n   ( " C o r e f i l e " ) .   F o r   m o r e   i n f o r m a t i o n ,   s e e   t h e   d o c u m e n t a t i o n   f o r   t h e   k u b e r n e t e s   C o r e D N S   p l u g i n ,   o r   r e a d   t h e   C u s t o m   D N S   E n t r i e s   f o r   K u b e r n e t e s .   i n   t h e   C o r e D N S   b l o g .


Question: What is Cluster Architecture?

Answer: This is the multi-page printable view of this section. Click here to print.Return to the regular view of this page.Cluster ArchitectureThe architectural concepts behind Kubernetes.1: Nodes2: Communication between Nodes and the Control Plane3: Controllers4: Leases5: Cloud Controller Manager6: About cgroup v27: Kubernetes Self-Healing8: Container Runtime Interface (CRI)9: Garbage Collection10: Mixed Version ProxyA Kubernetes cluster consists of a control plane plus a set of worker machines, called nodes, that run containerized applications. Every cluster needs at least one worker node in order to run Pods.The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.This document outlines the various components you need to have for a complete and working Kubernetes cluster.Figure 1. Kubernetes cluster components.About this architectureThe diagram in Figure 1 presents an example reference architecture for a Kubernetes cluster. The actual distribution of components can vary based on specific cluster setups and requirements.In the diagram, each node runs the kube-proxy component. You need a network proxy component on each node to ensure that the Service API and associated behaviors are available on your cluster network. However, some network plugins provide their own, third party implementation of proxying. When you use that kind of network plugin, the node does not need to run kube-proxy.Control plane componentsThe control plane's components make global decisions about the cluster (for example, scheduling), as well as detecting and responding to cluster events (for example, starting up a new pod when a Deployment's replicas field is unsatisfied).Control plane components can be run on any machine in the cluster. However, for simplicity, setup scripts typically start all control plane components on the same machine, and do not run user containers on this machine. See Creating Highly Available clusters with kubeadm for an example control plane setup that runs across multiple machines.kube-apiserverThe API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.The main implementation of a Kubernetes API server is kube-apiserver. kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. You can run several instances of kube-apiserver and balance traffic between those instances.etcdConsistent and highly-available key value store used as Kubernetes' backing store for all cluster data.If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data.You can find in-depth information about etcd in the official documenta


Question: How does Cluster Architecture work?

Answer: This is the multi-page printable view of this section. Click here to print.Return to the regular view of this page.Cluster ArchitectureThe architectural concepts behind Kubernetes.1: Nodes2: Communication between Nodes and the Control Plane3: Controllers4: Leases5: Cloud Controller Manager6: About cgroup v27: Kubernetes Self-Healing8: Container Runtime Interface (CRI)9: Garbage Collection10: Mixed Version ProxyA Kubernetes cluster consists of a control plane plus a set of worker machines, called nodes, that run containerized applications. Every cluster needs at least one worker node in order to run Pods.The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.This document outlines the various components you need to have for a complete and working Kubernetes cluster.Figure 1. Kubernetes cluster components.About this architectureThe diagram in Figure 1 presents an example reference architecture for a Kubernetes cluster. The actual distribution of components can vary based on specific cluster setups and requirements.In the diagram, each node runs the kube-proxy component. You need a network proxy component on each node to ensure that the Service API and associated behaviors are available on your cluster network. However, some network plugins provide their own, third party implementation of proxying. When you use that kind of network plugin, the node does not need to run kube-proxy.Control plane componentsThe control plane's components make global decisions about the cluster (for example, scheduling), as well as detecting and responding to cluster events (for example, starting up a new pod when a Deployment's replicas field is unsatisfied).Control plane components can be run on any machine in the cluster. However, for simplicity, setup scripts typically start all control plane components on the same machine, and do not run user containers on this machine. See Creating Highly Available clusters with kubeadm for an example control plane setup that runs across multiple machines.kube-apiserverThe API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.The main implementation of a Kubernetes API server is kube-apiserver. kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. You can run several instances of kube-apiserver and balance traffic between those instances.etcdConsistent and highly-available key value store used as Kubernetes' backing store for all cluster data.If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data.You can find in-depth information about etcd in the official documenta


Question: When would you use Cluster Architecture?

Answer: This is the multi-page printable view of this section. Click here to print.Return to the regular view of this page.Cluster ArchitectureThe architectural concepts behind Kubernetes.1: Nodes2: Communication between Nodes and the Control Plane3: Controllers4: Leases5: Cloud Controller Manager6: About cgroup v27: Kubernetes Self-Healing8: Container Runtime Interface (CRI)9: Garbage Collection10: Mixed Version ProxyA Kubernetes cluster consists of a control plane plus a set of worker machines, called nodes, that run containerized applications. Every cluster needs at least one worker node in order to run Pods.The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.This document outlines the various components you need to have for a complete and working Kubernetes cluster.Figure 1. Kubernetes cluster components.About this architectureThe diagram in Figure 1 presents an example reference architecture for a Kubernetes cluster. The actual distribution of components can vary based on specific cluster setups and requirements.In the diagram, each node runs the kube-proxy component. You need a network proxy component on each node to ensure that the Service API and associated behaviors are available on your cluster network. However, some network plugins provide their own, third party implementation of proxying. When you use that kind of network plugin, the node does not need to run kube-proxy.Control plane componentsThe control plane's components make global decisions about the cluster (for example, scheduling), as well as detecting and responding to cluster events (for example, starting up a new pod when a Deployment's replicas field is unsatisfied).Control plane components can be run on any machine in the cluster. However, for simplicity, setup scripts typically start all control plane components on the same machine, and do not run user containers on this machine. See Creating Highly Available clusters with kubeadm for an example control plane setup that runs across multiple machines.kube-apiserverThe API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.The main implementation of a Kubernetes API server is kube-apiserver. kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. You can run several instances of kube-apiserver and balance traffic between those instances.etcdConsistent and highly-available key value store used as Kubernetes' backing store for all cluster data.If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data.You can find in-depth information about etcd in the official documenta


Question: What are the benefits of Cluster Architecture?

Answer: This is the multi-page printable view of this section. Click here to print.Return to the regular view of this page.Cluster ArchitectureThe architectural concepts behind Kubernetes.1: Nodes2: Communication between Nodes and the Control Plane3: Controllers4: Leases5: Cloud Controller Manager6: About cgroup v27: Kubernetes Self-Healing8: Container Runtime Interface (CRI)9: Garbage Collection10: Mixed Version ProxyA Kubernetes cluster consists of a control plane plus a set of worker machines, called nodes, that run containerized applications. Every cluster needs at least one worker node in order to run Pods.The worker node(s) host the Pods that are the components of the application workload. The control plane manages the worker nodes and the Pods in the cluster. In production environments, the control plane usually runs across multiple computers and a cluster usually runs multiple nodes, providing fault-tolerance and high availability.This document outlines the various components you need to have for a complete and working Kubernetes cluster.Figure 1. Kubernetes cluster components.About this architectureThe diagram in Figure 1 presents an example reference architecture for a Kubernetes cluster. The actual distribution of components can vary based on specific cluster setups and requirements.In the diagram, each node runs the kube-proxy component. You need a network proxy component on each node to ensure that the Service API and associated behaviors are available on your cluster network. However, some network plugins provide their own, third party implementation of proxying. When you use that kind of network plugin, the node does not need to run kube-proxy.Control plane componentsThe control plane's components make global decisions about the cluster (for example, scheduling), as well as detecting and responding to cluster events (for example, starting up a new pod when a Deployment's replicas field is unsatisfied).Control plane components can be run on any machine in the cluster. However, for simplicity, setup scripts typically start all control plane components on the same machine, and do not run user containers on this machine. See Creating Highly Available clusters with kubeadm for an example control plane setup that runs across multiple machines.kube-apiserverThe API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.The main implementation of a Kubernetes API server is kube-apiserver. kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. You can run several instances of kube-apiserver and balance traffic between those instances.etcdConsistent and highly-available key value store used as Kubernetes' backing store for all cluster data.If your Kubernetes cluster uses etcd as its backing store, make sure you have a back up plan for the data.You can find in-depth information about etcd in the official documenta


Question: What is Cluster Architecture?

Answer: 1 :   N o d e s 2 :   C o m m u n i c a t i o n   b e t w e e n   N o d e s   a n d   t h e   C o n t r o l   P l a n e 3 :   C o n t r o l l e r s 4 :   L e a s e s 5 :   C l o u d   C o n t r o l l e r   M a n a g e r 6 :   A b o u t   c g r o u p   v 2 7 :   K u b e r n e t e s   S e l f - H e a l i n g 8 :   C o n t a i n e r   R u n t i m e   I n t e r f a c e   ( C R I ) 9 :   G a r b a g e   C o l l e c t i o n 1 0 :   M i x e d   V e r s i o n   P r o x y   A   K u b e r n e t e s   c l u s t e r   c o n s i s t s   o f   a   c o n t r o l   p l a n e   p l u s   a   s e t   o f   w o r k e r   m a c h i n e s ,   c a l l e d   n o d e s ,   t h a t   r u n   c o n t a i n e r i z e d   a p p l i c a t i o n s .   E v e r y   c l u s t e r   n e e d s   a t   l e a s t   o n e   w o r k e r   n o d e   i n   o r d e r   t o   r u n   P o d s .   T h e   w o r k e r   n o d e ( s )   h o s t   t h e   P o d s   t h a t   a r e   t h e   c o m p o n e n t s   o f   t h e   a p p l i c a t i o n   w o r k l o a d .   T h e   c o n t r o l   p l a n e   m a n a g e s   t h e   w o r k e r   n o d e s   a n d   t h e   P o d s   i n   t h e   c l u s t e r .   I n   p r o d u c t i o n   e n v i r o n m e n t s ,   t h e   c o n t r o l   p l a n e   u s u a l l y   r u n s   a c r o s s   m u l t i p l e   c o m p u t e r s   a n d   a   c l u s t e r   u s u a l l y   r u n s   m u l t i p l e   n o d e s ,   p r o v i d i n g   f a u l t - t o l e r a n c e   a n d   h i g h   a v a i l a b i l i t y .   T h i s   d o c u m e n t   o u t l i n e s   t h e   v a r i o u s   c o m p o n e n t s   y o u   n e e d   t o   h a v e   f o r   a   c o m p l e t e   a n d   w o r k i n g   K u b e r n e t e s   c l u s t e r .   F i g u r e   1 .   K u b e r n e t e s   c l u s t e r   c o m p o n e n t s .   T h e   d i a g r a m   i n   F i g u r e   1   p r e s e n t s   a n   e x a m p l e   r e f e r e n c e   a r c h i t e c t u r e   f o r   a   K u b e r n e t


Question: What is Control plane components?

Answer: T h e   c o n t r o l   p l a n e ' s   c o m p o n e n t s   m a k e   g l o b a l   d e c i s i o n s   a b o u t   t h e   c l u s t e r   ( f o r   e x a m p l e ,   s c h e d u l i n g ) ,   a s   w e l l   a s   d e t e c t i n g   a n d   r e s p o n d i n g   t o   c l u s t e r   e v e n t s   ( f o r   e x a m p l e ,   s t a r t i n g   u p   a   n e w   p o d   w h e n   a   D e p l o y m e n t ' s   r e p l i c a s   f i e l d   i s   u n s a t i s f i e d ) .   C o n t r o l   p l a n e   c o m p o n e n t s   c a n   b e   r u n   o n   a n y   m a c h i n e   i n   t h e   c l u s t e r .   H o w e v e r ,   f o r   s i m p l i c i t y ,   s e t u p   s c r i p t s   t y p i c a l l y   s t a r t   a l l   c o n t r o l   p l a n e   c o m p o n e n t s   o n   t h e   s a m e   m a c h i n e ,   a n d   d o   n o t   r u n   u s e r   c o n t a i n e r s   o n   t h i s   m a c h i n e .   S e e   C r e a t i n g   H i g h l y   A v a i l a b l e   c l u s t e r s   w i t h   k u b e a d m   f o r   a n   e x a m p l e   c o n t r o l   p l a n e   s e t u p   t h a t   r u n s   a c r o s s   m u l t i p l e   m a c h i n e s .


Question: What is kube-apiserver?

Answer: T h e   A P I   s e r v e r   i s   a   c o m p o n e n t   o f   t h e   K u b e r n e t e s   c o n t r o l   p l a n e   t h a t   e x p o s e s   t h e   K u b e r n e t e s   A P I .   T h e   A P I   s e r v e r   i s   t h e   f r o n t   e n d   f o r   t h e   K u b e r n e t e s   c o n t r o l   p l a n e .   T h e   m a i n   i m p l e m e n t a t i o n   o f   a   K u b e r n e t e s   A P I   s e r v e r   i s   k u b e - a p i s e r v e r .   k u b e - a p i s e r v e r   i s   d e s i g n e d   t o   s c a l e   h o r i z o n t a l l y — t h a t   i s ,   i t   s c a l e s   b y   d e p l o y i n g   m o r e   i n s t a n c e s .   Y o u   c a n   r u n   s e v e r a l   i n s t a n c e s   o f   k u b e - a p i s e r v e r   a n d   b a l a n c e   t r a f f i c   b e t w e e n   t h o s e   i n s t a n c e s .


Question: What is etcd?

Answer: C o n s i s t e n t   a n d   h i g h l y - a v a i l a b l e   k e y   v a l u e   s t o r e   u s e d   a s   K u b e r n e t e s '   b a c k i n g   s t o r e   f o r   a l l   c l u s t e r   d a t a .   I f   y o u r   K u b e r n e t e s   c l u s t e r   u s e s   e t c d   a s   i t s   b a c k i n g   s t o r e ,   m a k e   s u r e   y o u   h a v e   a   b a c k   u p   p l a n   f o r   t h e   d a t a .   Y o u   c a n   f i n d   i n - d e p t h   i n f o r m a t i o n   a b o u t   e t c d   i n   t h e   o f f i c i a l   d o c u m e n t a t i o n .


Question: What is kube-scheduler?

Answer: C o n t r o l   p l a n e   c o m p o n e n t   t h a t   w a t c h e s   f o r   n e w l y   c r e a t e d   P o d s   w i t h   n o   a s s i g n e d   n o d e ,   a n d   s e l e c t s   a   n o d e   f o r   t h e m   t o   r u n   o n .   F a c t o r s   t a k e n   i n t o   a c c o u n t   f o r   s c h e d u l i n g   d e c i s i o n s   i n c l u d e :   i n d i v i d u a l   a n d   c o l l e c t i v e   r e s o u r c e   r e q u i r e m e n t s ,   h a r d w a r e / s o f t w a r e / p o l i c y   c o n s t r a i n t s ,   a f f i n i t y   a n d   a n t i - a f f i n i t y   s p e c i f i c a t i o n s ,   d a t a   l o c a l i t y ,   i n t e r - w o r k l o a d   i n t e r f e r e n c e ,   a n d   d e a d l i n e s .


Question: What is kube-controller-manager?

Answer: C o n t r o l   p l a n e   c o m p o n e n t   t h a t   r u n s   c o n t r o l l e r   p r o c e s s e s .   L o g i c a l l y ,   e a c h   c o n t r o l l e r   i s   a   s e p a r a t e   p r o c e s s ,   b u t   t o   r e d u c e   c o m p l e x i t y ,   t h e y   a r e   a l l   c o m p i l e d   i n t o   a   s i n g l e   b i n a r y   a n d   r u n   i n   a   s i n g l e   p r o c e s s .   T h e r e   a r e   m a n y   d i f f e r e n t   t y p e s   o f   c o n t r o l l e r s .   S o m e   e x a m p l e s   o f   t h e m   a r e :   N o d e   c o n t r o l l e r :   R e s p o n s i b l e   f o r   n o t i c i n g   a n d   r e s p o n d i n g   w h e n   n o d e s   g o   d o w n . J o b   c o n t r o l l e r :   W a t c h e s   f o r   J o b   o b j e c t s   t h a t   r e p r e s e n t   o n e - o f f   t a s k s ,   t h e n   c r e a t e s   P o d s   t o   r u n   t h o s e   t a s k s   t o   c o m p l e t i o n . E n d p o i n t S l i c e   c o n t r o l l e r :   P o p u l a t e s   E n d p o i n t S l i c e   o b j e c t s   ( t o   p r o v i d e   a   l i n k   b e t w e e n   S e r v i c e s   a n d   P o d s ) . S e r v i c e A c c o u n t   c o n t r o l l e r :   C r e a t e   d e f a u l t   S e r v i c e A c c o u n t s   f o r   n e w   n a m e s p a c e s .   T h e   a b o v e   i s   n o t   a n   e x h a u s t i v e   l i s t .


Question: What is cloud-controller-manager?

Answer: T h e   c l o u d - c o n t r o l l e r - m a n a g e r   o n l y   r u n s   c o n t r o l l e r s   t h a t   a r e   s p e c i f i c   t o   y o u r   c l o u d   p r o v i d e r .   I f   y o u   a r e   r u n n i n g   K u b e r n e t e s   o n   y o u r   o w n   p r e m i s e s ,   o r   i n   a   l e a r n i n g   e n v i r o n m e n t   i n s i d e   y o u r   o w n   P C ,   t h e   c l u s t e r   d o e s   n o t   h a v e   a   c l o u d   c o n t r o l l e r   m a n a g e r .   A s   w i t h   t h e   k u b e - c o n t r o l l e r - m a n a g e r ,   t h e   c l o u d - c o n t r o l l e r - m a n a g e r   c o m b i n e s   s e v e r a l   l o g i c a l l y   i n d e p e n d e n t   c o n t r o l   l o o p s   i n t o   a   s i n g l e   b i n a r y   t h a t   y o u   r u n   a s   a   s i n g l e   p r o c e s s .   Y o u   c a n   s c a l e   h o r i z o n t a l l y   ( r u n   m o r e   t h a n   o n e   c o p y )   t o   i m p r o v e   p e r f o r m a n c e   o r   t o   h e l p   t o l e r a t e   f a i l u r e s .   T h e   f o l l o w i n g   c o n t r o l l e r s   c a n   h a v e   c l o u d   p r o v i d e r   d e p e n d e n c i e s :   N o d e   c o n t r o l l e r :   F o r   c h e c k i n g   t h e   c l o u d   p r o v i d e r   t o   d e t e r m i n e   i f   a   n o d e   h a s   b e e n   d e l e t e d   i n   t h e   c l o u d   a f t e r   i t   s t o p s   r e s p o n d i n g R o u t e   c o n t r o l l e r :   F o r   s e t t i n g   u p   r o u t e s   i n   t h e   u n d e r l y i n g   c l o u d   i n f r a s t r u c t u r e S e r v i c e   c o n t r o l l e r :   F o r   c r e a t i n g ,   u p d a t i n g   a n d   d e l e t i n g   c l o u d   p r o v i d e r   l o a d   b a l a n c e r s


Question: What is Node components?

Answer: N o d e   c o m p o n e n t s   r u n   o n   e v e r y   n o d e ,   m a i n t a i n i n g   r u n n i n g   p o d s   a n d   p r o v i d i n g   t h e   K u b e r n e t e s   r u n t i m e   e n v i r o n m e n t .


Question: What is kubelet?

Answer: A n   a g e n t   t h a t   r u n s   o n   e a c h   n o d e   i n   t h e   c l u s t e r .   I t   m a k e s   s u r e   t h a t   c o n t a i n e r s   a r e   r u n n i n g   i n   a   P o d .   T h e   k u b e l e t   t a k e s   a   s e t   o f   P o d S p e c s   t h a t   a r e   p r o v i d e d   t h r o u g h   v a r i o u s   m e c h a n i s m s   a n d   e n s u r e s   t h a t   t h e   c o n t a i n e r s   d e s c r i b e d   i n   t h o s e   P o d S p e c s   a r e   r u n n i n g   a n d   h e a l t h y .   T h e   k u b e l e t   d o e s n ' t   m a n a g e   c o n t a i n e r s   w h i c h   w e r e   n o t   c r e a t e d   b y   K u b e r n e t e s .


Question: What is kube-proxy (optional)?

Answer: k u b e - p r o x y   i s   a   n e t w o r k   p r o x y   t h a t   r u n s   o n   e a c h   n o d e   i n   y o u r   c l u s t e r ,   i m p l e m e n t i n g   p a r t   o f   t h e   K u b e r n e t e s   S e r v i c e   c o n c e p t . k u b e - p r o x y   m a i n t a i n s   n e t w o r k   r u l e s   o n   n o d e s .   T h e s e   n e t w o r k   r u l e s   a l l o w   n e t w o r k   c o m m u n i c a t i o n   t o   y o u r   P o d s   f r o m   n e t w o r k   s e s s i o n s   i n s i d e   o r   o u t s i d e   o f   y o u r   c l u s t e r . k u b e - p r o x y   u s e s   t h e   o p e r a t i n g   s y s t e m   p a c k e t   f i l t e r i n g   l a y e r   i f   t h e r e   i s   o n e   a n d   i t ' s   a v a i l a b l e .   O t h e r w i s e ,   k u b e - p r o x y   f o r w a r d s   t h e   t r a f f i c   i t s e l f . I f   y o u   u s e   a   n e t w o r k   p l u g i n   t h a t   i m p l e m e n t s   p a c k e t   f o r w a r d i n g   f o r   S e r v i c e s   b y   i t s e l f ,   a n d   p r o v i d i n g   e q u i v a l e n t   b e h a v i o r   t o   k u b e - p r o x y ,   t h e n   y o u   d o   n o t   n e e d   t o   r u n   k u b e - p r o x y   o n   t h e   n o d e s   i n   y o u r   c l u s t e r .   k u b e - p r o x y   i s   a   n e t w o r k   p r o x y   t h a t   r u n s   o n   e a c h   n o d e   i n   y o u r   c l u s t e r ,   i m p l e m e n t i n g   p a r t   o f   t h e   K u b e r n e t e s   S e r v i c e   c o n c e p t .   k u b e - p r o x y   m a i n t a i n s   n e t w o r k   r u l e s   o n   n o d e s .   T h e s e   n e t w o r k   r u l e s   a l l o w   n e t w o r k   c o m m u n i c a t i o n   t o   y o u r   P o d s   f r o m   n e t w o r k   s e s s i o n s   i n s i d e   o r   o u t s i d e   o f   y o u r   c l u s t e r .   k u b e - p r o x y   u s e s   t h e   o p e r a t i n g   s y s t e m   p a c k e t   f i l t e r i n g   l a y e r   i f   t h e r e   i s   o n e   a n d


Question: What is Container runtime?

Answer: A   f u n d a m e n t a l   c o m p o n e n t   t h a t   e m p o w e r s   K u b e r n e t e s   t o   r u n   c o n t a i n e r s   e f f e c t i v e l y .   I t   i s   r e s p o n s i b l e   f o r   m a n a g i n g   t h e   e x e c u t i o n   a n d   l i f e c y c l e   o f   c o n t a i n e r s   w i t h i n   t h e   K u b e r n e t e s   e n v i r o n m e n t .   K u b e r n e t e s   s u p p o r t s   c o n t a i n e r   r u n t i m e s   s u c h   a s   c o n t a i n e r d ,   C R I - O ,   a n d   a n y   o t h e r   i m p l e m e n t a t i o n   o f   t h e   K u b e r n e t e s   C R I   ( C o n t a i n e r   R u n t i m e   I n t e r f a c e ) .


Question: What is Addons?

Answer: A d d o n s   u s e   K u b e r n e t e s   r e s o u r c e s   ( D a e m o n S e t ,   D e p l o y m e n t ,   e t c )   t o   i m p l e m e n t   c l u s t e r   f e a t u r e s .   B e c a u s e   t h e s e   a r e   p r o v i d i n g   c l u s t e r - l e v e l   f e a t u r e s ,   n a m e s p a c e d   r e s o u r c e s   f o r   a d d o n s   b e l o n g   w i t h i n   t h e   k u b e - s y s t e m   n a m e s p a c e .   S e l e c t e d   a d d o n s   a r e   d e s c r i b e d   b e l o w ;   f o r   a n   e x t e n d e d   l i s t   o f   a v a i l a b l e   a d d o n s ,   p l e a s e   s e e   A d d o n s .


Question: What is DNS?

Answer: W h i l e   t h e   o t h e r   a d d o n s   a r e   n o t   s t r i c t l y   r e q u i r e d ,   a l l   K u b e r n e t e s   c l u s t e r s   s h o u l d   h a v e   c l u s t e r   D N S ,   a s   m a n y   e x a m p l e s   r e l y   o n   i t .   C l u s t e r   D N S   i s   a   D N S   s e r v e r ,   i n   a d d i t i o n   t o   t h e   o t h e r   D N S   s e r v e r ( s )   i n   y o u r   e n v i r o n m e n t ,   w h i c h   s e r v e s   D N S   r e c o r d s   f o r   K u b e r n e t e s   s e r v i c e s .   C o n t a i n e r s   s t a r t e d   b y   K u b e r n e t e s   a u t o m a t i c a l l y   i n c l u d e   t h i s   D N S   s e r v e r   i n   t h e i r   D N S   s e a r c h e s .


Question: What is Web UI (Dashboard)?

Answer: D a s h b o a r d   i s   a   g e n e r a l   p u r p o s e ,   w e b - b a s e d   U I   f o r   K u b e r n e t e s   c l u s t e r s .   I t   a l l o w s   u s e r s   t o   m a n a g e   a n d   t r o u b l e s h o o t   a p p l i c a t i o n s   r u n n i n g   i n   t h e   c l u s t e r ,   a s   w e l l   a s   t h e   c l u s t e r   i t s e l f .


Question: What is Container resource monitoring?

Answer: C o n t a i n e r   R e s o u r c e   M o n i t o r i n g   r e c o r d s   g e n e r i c   t i m e - s e r i e s   m e t r i c s   a b o u t   c o n t a i n e r s   i n   a   c e n t r a l   d a t a b a s e ,   a n d   p r o v i d e s   a   U I   f o r   b r o w s i n g   t h a t   d a t a .


Question: What is Cluster-level Logging?

Answer: A   c l u s t e r - l e v e l   l o g g i n g   m e c h a n i s m   i s   r e s p o n s i b l e   f o r   s a v i n g   c o n t a i n e r   l o g s   t o   a   c e n t r a l   l o g   s t o r e   w i t h   a   s e a r c h / b r o w s i n g   i n t e r f a c e .


Question: What is Network plugins?

Answer: N e t w o r k   p l u g i n s   a r e   s o f t w a r e   c o m p o n e n t s   t h a t   i m p l e m e n t   t h e   c o n t a i n e r   n e t w o r k   i n t e r f a c e   ( C N I )   s p e c i f i c a t i o n .   T h e y   a r e   r e s p o n s i b l e   f o r   a l l o c a t i n g   I P   a d d r e s s e s   t o   p o d s   a n d   e n a b l i n g   t h e m   t o   c o m m u n i c a t e   w i t h   e a c h   o t h e r   w i t h i n   t h e   c l u s t e r .


Question: What is Architecture variations?

Answer: W h i l e   t h e   c o r e   c o m p o n e n t s   o f   K u b e r n e t e s   r e m a i n   c o n s i s t e n t ,   t h e   w a y   t h e y   a r e   d e p l o y e d   a n d   m a n a g e d   c a n   v a r y .   U n d e r s t a n d i n g   t h e s e   v a r i a t i o n s   i s   c r u c i a l   f o r   d e s i g n i n g   a n d   m a i n t a i n i n g   K u b e r n e t e s   c l u s t e r s   t h a t   m e e t   s p e c i f i c   o p e r a t i o n a l   n e e d s .


Question: What is Control plane deployment options?

Answer: T h e   c o n t r o l   p l a n e   c o m p o n e n t s   c a n   b e   d e p l o y e d   i n   s e v e r a l   w a y s :


Question: What is Workload placement considerations?

Answer: T h e   p l a c e m e n t   o f   w o r k l o a d s ,   i n c l u d i n g   t h e   c o n t r o l   p l a n e   c o m p o n e n t s ,   c a n   v a r y   b a s e d   o n   c l u s t e r   s i z e ,   p e r f o r m a n c e   r e q u i r e m e n t s ,   a n d   o p e r a t i o n a l   p o l i c i e s :   I n   s m a l l e r   o r   d e v e l o p m e n t   c l u s t e r s ,   c o n t r o l   p l a n e   c o m p o n e n t s   a n d   u s e r   w o r k l o a d s   m i g h t   r u n   o n   t h e   s a m e   n o d e s . L a r g e r   p r o d u c t i o n   c l u s t e r s   o f t e n   d e d i c a t e   s p e c i f i c   n o d e s   t o   c o n t r o l   p l a n e   c o m p o n e n t s ,   s e p a r a t i n g   t h e m   f r o m   u s e r   w o r k l o a d s . S o m e   o r g a n i z a t i o n s   r u n   c r i t i c a l   a d d - o n s   o r   m o n i t o r i n g   t o o l s   o n   c o n t r o l   p l a n e   n o d e s .


Question: What is Cluster management tools?

Answer: T o o l s   l i k e   k u b e a d m ,   k o p s ,   a n d   K u b e s p r a y   o f f e r   d i f f e r e n t   a p p r o a c h e s   t o   d e p l o y i n g   a n d   m a n a g i n g   c l u s t e r s ,   e a c h   w i t h   i t s   o w n   m e t h o d   o f   c o m p o n e n t   l a y o u t   a n d   m a n a g e m e n t .   T h e   f l e x i b i l i t y   o f   K u b e r n e t e s   a r c h i t e c t u r e   a l l o w s   o r g a n i z a t i o n s   t o   t a i l o r   t h e i r   c l u s t e r s   t o   s p e c i f i c   n e e d s ,   b a l a n c i n g   f a c t o r s   s u c h   a s   o p e r a t i o n a l   c o m p l e x i t y ,   p e r f o r m a n c e ,   a n d   m a n a g e m e n t   o v e r h e a d .


Question: What is Customization and extensibility?

Answer: K u b e r n e t e s   a r c h i t e c t u r e   a l l o w s   f o r   s i g n i f i c a n t   c u s t o m i z a t i o n :   C u s t o m   s c h e d u l e r s   c a n   b e   d e p l o y e d   t o   w o r k   a l o n g s i d e   t h e   d e f a u l t   K u b e r n e t e s   s c h e d u l e r   o r   t o   r e p l a c e   i t   e n t i r e l y . A P I   s e r v e r s   c a n   b e   e x t e n d e d   w i t h   C u s t o m R e s o u r c e D e f i n i t i o n s   a n d   A P I   A g g r e g a t i o n . C l o u d   p r o v i d e r s   c a n   i n t e g r a t e   d e e p l y   w i t h   K u b e r n e t e s   u s i n g   t h e   c l o u d - c o n t r o l l e r - m a n a g e r .   T h e   f l e x i b i l i t y   o f   K u b e r n e t e s   a r c h i t e c t u r e   a l l o w s   o r g a n i z a t i o n s   t o   t a i l o r   t h e i r   c l u s t e r s   t o   s p e c i f i c   n e e d s ,   b a l a n c i n g   f a c t o r s   s u c h   a s   o p e r a t i o n a l   c o m p l e x i t y ,   p e r f o r m a n c e ,   a n d   m a n a g e m e n t   o v e r h e a d .


Question: What is What's next?

Answer: L e a r n   m o r e   a b o u t   t h e   f o l l o w i n g :   N o d e s   a n d   t h e i r   c o m m u n i c a t i o n   w i t h   t h e   c o n t r o l   p l a n e . K u b e r n e t e s   c o n t r o l l e r s . k u b e - s c h e d u l e r   w h i c h   i s   t h e   d e f a u l t   s c h e d u l e r   f o r   K u b e r n e t e s . E t c d ' s   o f f i c i a l   d o c u m e n t a t i o n . S e v e r a l   c o n t a i n e r   r u n t i m e s   i n   K u b e r n e t e s . I n t e g r a t i n g   w i t h   c l o u d   p r o v i d e r s   u s i n g   c l o u d - c o n t r o l l e r - m a n a g e r . k u b e c t l   c o m m a n d s .


Question: What is 1 - Nodes?

Answer: K u b e r n e t e s   r u n s   y o u r   w o r k l o a d   b y   p l a c i n g   c o n t a i n e r s   i n t o   P o d s   t o   r u n   o n   N o d e s .   A   n o d e   m a y   b e   a   v i r t u a l   o r   p h y s i c a l   m a c h i n e ,   d e p e n d i n g   o n   t h e   c l u s t e r .   E a c h   n o d e   i s   m a n a g e d   b y   t h e   c o n t r o l   p l a n e   a n d   c o n t a i n s   t h e   s e r v i c e s   n e c e s s a r y   t o   r u n   P o d s .   T y p i c a l l y   y o u   h a v e   s e v e r a l   n o d e s   i n   a   c l u s t e r ;   i n   a   l e a r n i n g   o r   r e s o u r c e - l i m i t e d   e n v i r o n m e n t ,   y o u   m i g h t   h a v e   o n l y   o n e   n o d e .   T h e   c o m p o n e n t s   o n   a   n o d e   i n c l u d e   t h e   k u b e l e t ,   a   c o n t a i n e r   r u n t i m e ,   a n d   t h e   k u b e - p r o x y .


Question: What is Management?

Answer: T h e r e   a r e   t w o   m a i n   w a y s   t o   h a v e   N o d e s   a d d e d   t o   t h e   A P I   s e r v e r :   T h e   k u b e l e t   o n   a   n o d e   s e l f - r e g i s t e r s   t o   t h e   c o n t r o l   p l a n e Y o u   ( o r   a n o t h e r   h u m a n   u s e r )   m a n u a l l y   a d d   a   N o d e   o b j e c t   A f t e r   y o u   c r e a t e   a   N o d e   o b j e c t ,   o r   t h e   k u b e l e t   o n   a   n o d e   s e l f - r e g i s t e r s ,   t h e   c o n t r o l   p l a n e   c h e c k s   w h e t h e r   t h e   n e w   N o d e   o b j e c t   i s   v a l i d .   F o r   e x a m p l e ,   i f   y o u   t r y   t o   c r e a t e   a   N o d e   f r o m   t h e   f o l l o w i n g   J S O N   m a n i f e s t :   {   " k i n d " :   " N o d e " ,   " a p i V e r s i o n " :   " v 1 " ,   " m e t a d a t a " :   {   " n a m e " :   " 1 0 . 2 4 0 . 7 9 . 1 5 7 " ,   " l a b e l s " :   {   " n a m e " :   " m y - f i r s t - k 8 s - n o d e "   }   }   }   K u b e r n e t e s   c r e a t e s   a   N o d e   o b j e c t   i n t e r n a l l y   ( t h e   r e p r e s e n t a t i o n ) .   K u b e r n e t e s   c h e c k s   t h a t   a   k u b e l e t   h a s   r e g i s t e r e d   t o   t h e   A P I   s e r v e r   t h a t   m a t c h e s   t h e   m e t a d a t a . n a m e   f i e l d   o f   t h e   N o d e .   I f   t h e   n o d e   i s   h e a l t h y   ( i . e .   a l l   n e c e s s a r y   s e r v i c e s   a r e   r u n n i n g ) ,   t h e n   i t   i s   e l i g i b l e   t o   r u n   a   P o d .   O t h e r w i s e ,   t h a t   n o d e   i s   i g n o r e d   f o r   a n y   c l u s t e r   a c t i v i t y   u n t i l   i t   b e c o m e s   h e a l t h y .


Question: What is Note:?

Answer: K u b e r n e t e s   k e e p s   t h e   o b j e c t   f o r   t h e   i n v a l i d   N o d e   a n d   c o n t i n u e s   c h e c k i n g   t o   s e e   w h e t h e r   i t   b e c o m e s   h e a l t h y .   Y o u ,   o r   a   c o n t r o l l e r ,   m u s t   e x p l i c i t l y   d e l e t e   t h e   N o d e   o b j e c t   t o   s t o p   t h a t   h e a l t h   c h e c k i n g .   T h e   n a m e   o f   a   N o d e   o b j e c t   m u s t   b e   a   v a l i d   D N S   s u b d o m a i n   n a m e .


Question: What is Node name uniqueness?

Answer: T h e   n a m e   i d e n t i f i e s   a   N o d e .   T w o   N o d e s   c a n n o t   h a v e   t h e   s a m e   n a m e   a t   t h e   s a m e   t i m e .   K u b e r n e t e s   a l s o   a s s u m e s   t h a t   a   r e s o u r c e   w i t h   t h e   s a m e   n a m e   i s   t h e   s a m e   o b j e c t .   I n   c a s e   o f   a   N o d e ,   i t   i s   i m p l i c i t l y   a s s u m e d   t h a t   a n   i n s t a n c e   u s i n g   t h e   s a m e   n a m e   w i l l   h a v e   t h e   s a m e   s t a t e   ( e . g .   n e t w o r k   s e t t i n g s ,   r o o t   d i s k   c o n t e n t s )   a n d   a t t r i b u t e s   l i k e   n o d e   l a b e l s .   T h i s   m a y   l e a d   t o   i n c o n s i s t e n c i e s   i f   a n   i n s t a n c e   w a s   m o d i f i e d   w i t h o u t   c h a n g i n g   i t s   n a m e .   I f   t h e   N o d e   n e e d s   t o   b e   r e p l a c e d   o r   u p d a t e d   s i g n i f i c a n t l y ,   t h e   e x i s t i n g   N o d e   o b j e c t   n e e d s   t o   b e   r e m o v e d   f r o m   A P I   s e r v e r   f i r s t   a n d   r e - a d d e d   a f t e r   t h e   u p d a t e .


Question: What is Self-registration of Nodes?

Answer: W h e n   t h e   k u b e l e t   f l a g   - - r e g i s t e r - n o d e   i s   t r u e   ( t h e   d e f a u l t ) ,   t h e   k u b e l e t   w i l l   a t t e m p t   t o   r e g i s t e r   i t s e l f   w i t h   t h e   A P I   s e r v e r .   T h i s   i s   t h e   p r e f e r r e d   p a t t e r n ,   u s e d   b y   m o s t   d i s t r o s .   F o r   s e l f - r e g i s t r a t i o n ,   t h e   k u b e l e t   i s   s t a r t e d   w i t h   t h e   f o l l o w i n g   o p t i o n s :   - - k u b e c o n f i g   -   P a t h   t o   c r e d e n t i a l s   t o   a u t h e n t i c a t e   i t s e l f   t o   t h e   A P I   s e r v e r . - - c l o u d - p r o v i d e r   -   H o w   t o   t a l k   t o   a   c l o u d   p r o v i d e r   t o   r e a d   m e t a d a t a   a b o u t   i t s e l f . - - r e g i s t e r - n o d e   -   A u t o m a t i c a l l y   r e g i s t e r   w i t h   t h e   A P I   s e r v e r . - - r e g i s t e r - w i t h - t a i n t s   -   R e g i s t e r   t h e   n o d e   w i t h   t h e   g i v e n   l i s t   o f   t a i n t s   ( c o m m a   s e p a r a t e d   < k e y > = < v a l u e > : < e f f e c t > ) . N o - o p   i f   r e g i s t e r - n o d e   i s   f a l s e . - - n o d e - i p   -   O p t i o n a l   c o m m a - s e p a r a t e d   l i s t   o f   t h e   I P   a d d r e s s e s   f o r   t h e   n o d e .   Y o u   c a n   o n l y   s p e c i f y   a   s i n g l e   a d d r e s s   f o r   e a c h   a d d r e s s   f a m i l y .   F o r   e x a m p l e ,   i n   a   s i n g l e - s t a c k   I P v 4   c l u s t e r ,   y o u   s e t   t h i s   v a l u e   t o   b e   t h e   I P v 4   a d d r e s s   t h a t   t h e   k u b e l e t   s h o u l d   u s e   f o r   t h e   n o d e .   S e e   c o n f i g u r e   I P v 4 / I P v 6   d u a l   s t a c k   f o r   d e t a i l s   o f   r u n n i n g   a   d u a l - s t a c k   c l u s t e r . I f   y o u   d o n ' t   p r o v i d e   t h i s   a r g u m e n t ,


Question: What is Note:?

Answer: A s   m e n t i o n e d   i n   t h e   N o d e   n a m e   u n i q u e n e s s   s e c t i o n ,   w h e n   N o d e   c o n f i g u r a t i o n   n e e d s   t o   b e   u p d a t e d ,   i t   i s   a   g o o d   p r a c t i c e   t o   r e - r e g i s t e r   t h e   n o d e   w i t h   t h e   A P I   s e r v e r .   F o r   e x a m p l e ,   i f   t h e   k u b e l e t   i s   b e i n g   r e s t a r t e d   w i t h   a   n e w   s e t   o f   - - n o d e - l a b e l s ,   b u t   t h e   s a m e   N o d e   n a m e   i s   u s e d ,   t h e   c h a n g e   w i l l   n o t   t a k e   e f f e c t ,   a s   l a b e l s   a r e   o n l y   s e t   ( o r   m o d i f i e d )   u p o n   N o d e   r e g i s t r a t i o n   w i t h   t h e   A P I   s e r v e r .   P o d s   a l r e a d y   s c h e d u l e d   o n   t h e   N o d e   m a y   m i s b e h a v e   o r   c a u s e   i s s u e s   i f   t h e   N o d e   c o n f i g u r a t i o n   w i l l   b e   c h a n g e d   o n   k u b e l e t   r e s t a r t .   F o r   e x a m p l e ,   a l r e a d y   r u n n i n g   P o d   m a y   b e   t a i n t e d   a g a i n s t   t h e   n e w   l a b e l s   a s s i g n e d   t o   t h e   N o d e ,   w h i l e   o t h e r   P o d s ,   t h a t   a r e   i n c o m p a t i b l e   w i t h   t h a t   P o d   w i l l   b e   s c h e d u l e d   b a s e d   o n   t h i s   n e w   l a b e l .   N o d e   r e - r e g i s t r a t i o n   e n s u r e s   a l l   P o d s   w i l l   b e   d r a i n e d   a n d   p r o p e r l y   r e - s c h e d u l e d .


Question: What is Manual Node administration?

Answer: Y o u   c a n   c r e a t e   a n d   m o d i f y   N o d e   o b j e c t s   u s i n g   k u b e c t l .   W h e n   y o u   w a n t   t o   c r e a t e   N o d e   o b j e c t s   m a n u a l l y ,   s e t   t h e   k u b e l e t   f l a g   - - r e g i s t e r - n o d e = f a l s e .   Y o u   c a n   m o d i f y   N o d e   o b j e c t s   r e g a r d l e s s   o f   t h e   s e t t i n g   o f   - - r e g i s t e r - n o d e .   F o r   e x a m p l e ,   y o u   c a n   s e t   l a b e l s   o n   a n   e x i s t i n g   N o d e   o r   m a r k   i t   u n s c h e d u l a b l e .   Y o u   c a n   s e t   o p t i o n a l   n o d e   r o l e ( s )   f o r   n o d e s   b y   a d d i n g   o n e   o r   m o r e   n o d e - r o l e . k u b e r n e t e s . i o / < r o l e > :   < r o l e >   l a b e l s   t o   t h e   n o d e   w h e r e   c h a r a c t e r s   o f   < r o l e >   a r e   l i m i t e d   b y   t h e   s y n t a x   r u l e s   f o r   l a b e l s .   K u b e r n e t e s   i g n o r e s   t h e   l a b e l   v a l u e   f o r   n o d e   r o l e s ;   b y   c o n v e n t i o n ,   y o u   c a n   s e t   i t   t o   t h e   s a m e   s t r i n g   y o u   u s e d   f o r   t h e   n o d e   r o l e   i n   t h e   l a b e l   k e y .   Y o u   c a n   u s e   l a b e l s   o n   N o d e s   i n   c o n j u n c t i o n   w i t h   n o d e   s e l e c t o r s   o n   P o d s   t o   c o n t r o l   s c h e d u l i n g .   F o r   e x a m p l e ,   y o u   c a n   c o n s t r a i n   a   P o d   t o   o n l y   b e   e l i g i b l e   t o   r u n   o n   a   s u b s e t   o f   t h e   a v a i l a b l e   n o d e s .   M a r k i n g   a   n o d e   a s   u n s c h e d u l a b l e   p r e v e n t s   t h e   s c h e d u l e r   f r o m   p l a c i n g   n e w   p o d s   o n t o   t h a t   N o d e   b u t   d o e s   n o t   a f f e c t   e x i s t i n g   P o d s   o n   t h e   N o d e .   T h i s   i s   u s e f u l   a s   a   p r e p a r a t o r


Question: What is Node status?

Answer: A   N o d e ' s   s t a t u s   c o n t a i n s   t h e   f o l l o w i n g   i n f o r m a t i o n :   A d d r e s s e s C o n d i t i o n s C a p a c i t y   a n d   A l l o c a t a b l e I n f o   Y o u   c a n   u s e   k u b e c t l   t o   v i e w   a   N o d e ' s   s t a t u s   a n d   o t h e r   d e t a i l s :   k u b e c t l   d e s c r i b e   n o d e   < i n s e r t - n o d e - n a m e - h e r e >   S e e   N o d e   S t a t u s   f o r   m o r e   d e t a i l s .


Question: What is Node heartbeats?

Answer: H e a r t b e a t s ,   s e n t   b y   K u b e r n e t e s   n o d e s ,   h e l p   y o u r   c l u s t e r   d e t e r m i n e   t h e   a v a i l a b i l i t y   o f   e a c h   n o d e ,   a n d   t o   t a k e   a c t i o n   w h e n   f a i l u r e s   a r e   d e t e c t e d .   F o r   n o d e s   t h e r e   a r e   t w o   f o r m s   o f   h e a r t b e a t s :   U p d a t e s   t o   t h e   . s t a t u s   o f   a   N o d e . L e a s e   o b j e c t s   w i t h i n   t h e   k u b e - n o d e - l e a s e   n a m e s p a c e .   E a c h   N o d e   h a s   a n   a s s o c i a t e d   L e a s e   o b j e c t .


Question: What is Node controller?

Answer: T h e   n o d e   c o n t r o l l e r   i s   a   K u b e r n e t e s   c o n t r o l   p l a n e   c o m p o n e n t   t h a t   m a n a g e s   v a r i o u s   a s p e c t s   o f   n o d e s .   T h e   n o d e   c o n t r o l l e r   h a s   m u l t i p l e   r o l e s   i n   a   n o d e ' s   l i f e .   T h e   f i r s t   i s   a s s i g n i n g   a   C I D R   b l o c k   t o   t h e   n o d e   w h e n   i t   i s   r e g i s t e r e d   ( i f   C I D R   a s s i g n m e n t   i s   t u r n e d   o n ) .   T h e   s e c o n d   i s   k e e p i n g   t h e   n o d e   c o n t r o l l e r ' s   i n t e r n a l   l i s t   o f   n o d e s   u p   t o   d a t e   w i t h   t h e   c l o u d   p r o v i d e r ' s   l i s t   o f   a v a i l a b l e   m a c h i n e s .   W h e n   r u n n i n g   i n   a   c l o u d   e n v i r o n m e n t   a n d   w h e n e v e r   a   n o d e   i s   u n h e a l t h y ,   t h e   n o d e   c o n t r o l l e r   a s k s   t h e   c l o u d   p r o v i d e r   i f   t h e   V M   f o r   t h a t   n o d e   i s   s t i l l   a v a i l a b l e .   I f   n o t ,   t h e   n o d e   c o n t r o l l e r   d e l e t e s   t h e   n o d e   f r o m   i t s   l i s t   o f   n o d e s .   T h e   t h i r d   i s   m o n i t o r i n g   t h e   n o d e s '   h e a l t h .   T h e   n o d e   c o n t r o l l e r   i s   r e s p o n s i b l e   f o r :   I n   t h e   c a s e   t h a t   a   n o d e   b e c o m e s   u n r e a c h a b l e ,   u p d a t i n g   t h e   R e a d y   c o n d i t i o n   i n   t h e   N o d e ' s   . s t a t u s   f i e l d .   I n   t h i s   c a s e   t h e   n o d e   c o n t r o l l e r   s e t s   t h e   R e a d y   c o n d i t i o n   t o   U n k n o w n . I f   a   n o d e   r e m a i n s   u n r e a c h a b l e :   t r i g g e r i n g   A P I - i n i t i a t e d   e v i c t i o n   f o r   a l l   o f   t h e   P o d s   o n   t h e   u n r e a c h a b l e   n o d e .   B y   d e f a u l t ,   t h e


Question: What is Rate limits on eviction?

Answer: I n   m o s t   c a s e s ,   t h e   n o d e   c o n t r o l l e r   l i m i t s   t h e   e v i c t i o n   r a t e   t o   - - n o d e - e v i c t i o n - r a t e   ( d e f a u l t   0 . 1 )   p e r   s e c o n d ,   m e a n i n g   i t   w o n ' t   e v i c t   p o d s   f r o m   m o r e   t h a n   1   n o d e   p e r   1 0   s e c o n d s .   T h e   n o d e   e v i c t i o n   b e h a v i o r   c h a n g e s   w h e n   a   n o d e   i n   a   g i v e n   a v a i l a b i l i t y   z o n e   b e c o m e s   u n h e a l t h y .   T h e   n o d e   c o n t r o l l e r   c h e c k s   w h a t   p e r c e n t a g e   o f   n o d e s   i n   t h e   z o n e   a r e   u n h e a l t h y   ( t h e   R e a d y   c o n d i t i o n   i s   U n k n o w n   o r   F a l s e )   a t   t h e   s a m e   t i m e :   I f   t h e   f r a c t i o n   o f   u n h e a l t h y   n o d e s   i s   a t   l e a s t   - - u n h e a l t h y - z o n e - t h r e s h o l d   ( d e f a u l t   0 . 5 5 ) ,   t h e n   t h e   e v i c t i o n   r a t e   i s   r e d u c e d . I f   t h e   c l u s t e r   i s   s m a l l   ( i . e .   h a s   l e s s   t h a n   o r   e q u a l   t o   - - l a r g e - c l u s t e r - s i z e - t h r e s h o l d   n o d e s   -   d e f a u l t   5 0 ) ,   t h e n   e v i c t i o n s   a r e   s t o p p e d . O t h e r w i s e ,   t h e   e v i c t i o n   r a t e   i s   r e d u c e d   t o   - - s e c o n d a r y - n o d e - e v i c t i o n - r a t e   ( d e f a u l t   0 . 0 1 )   p e r   s e c o n d .   T h e   r e a s o n   t h e s e   p o l i c i e s   a r e   i m p l e m e n t e d   p e r   a v a i l a b i l i t y   z o n e   i s   b e c a u s e   o n e   a v a i l a b i l i t y   z o n e   m i g h t   b e c o m e   p a r t i t i o n e d   f r o m   t h e   c o n t r o l   p l a n e   w h i l e   t h e   o t h e r s   r e m a i n   c o n n e c t e d .   I f   y o u r   c l u s t e r   d o e s   n o t   s p a n   m u l t i p l e   c l o u d   p r o v i d


Question: What is Resource capacity tracking?

Answer: N o d e   o b j e c t s   t r a c k   i n f o r m a t i o n   a b o u t   t h e   N o d e ' s   r e s o u r c e   c a p a c i t y :   f o r   e x a m p l e ,   t h e   a m o u n t   o f   m e m o r y   a v a i l a b l e   a n d   t h e   n u m b e r   o f   C P U s .   N o d e s   t h a t   s e l f   r e g i s t e r   r e p o r t   t h e i r   c a p a c i t y   d u r i n g   r e g i s t r a t i o n .   I f   y o u   m a n u a l l y   a d d   a   N o d e ,   t h e n   y o u   n e e d   t o   s e t   t h e   n o d e ' s   c a p a c i t y   i n f o r m a t i o n   w h e n   y o u   a d d   i t .   T h e   K u b e r n e t e s   s c h e d u l e r   e n s u r e s   t h a t   t h e r e   a r e   e n o u g h   r e s o u r c e s   f o r   a l l   t h e   P o d s   o n   a   N o d e .   T h e   s c h e d u l e r   c h e c k s   t h a t   t h e   s u m   o f   t h e   r e q u e s t s   o f   c o n t a i n e r s   o n   t h e   n o d e   i s   n o   g r e a t e r   t h a n   t h e   n o d e ' s   c a p a c i t y .   T h a t   s u m   o f   r e q u e s t s   i n c l u d e s   a l l   c o n t a i n e r s   m a n a g e d   b y   t h e   k u b e l e t ,   b u t   e x c l u d e s   a n y   c o n t a i n e r s   s t a r t e d   d i r e c t l y   b y   t h e   c o n t a i n e r   r u n t i m e ,   a n d   a l s o   e x c l u d e s   a n y   p r o c e s s e s   r u n n i n g   o u t s i d e   o f   t h e   k u b e l e t ' s   c o n t r o l .


Question: What is Node topology?

Answer: I f   y o u   h a v e   e n a b l e d   t h e   T o p o l o g y M a n a g e r   f e a t u r e   g a t e ,   t h e n   t h e   k u b e l e t   c a n   u s e   t o p o l o g y   h i n t s   w h e n   m a k i n g   r e s o u r c e   a s s i g n m e n t   d e c i s i o n s .   S e e   C o n t r o l   T o p o l o g y   M a n a g e m e n t   P o l i c i e s   o n   a   N o d e   f o r   m o r e   i n f o r m a t i o n .


Question: What is What's next?

Answer: L e a r n   m o r e   a b o u t   t h e   f o l l o w i n g :   C o m p o n e n t s   t h a t   m a k e   u p   a   n o d e . A P I   d e f i n i t i o n   f o r   N o d e . N o d e   s e c t i o n   o f   t h e   a r c h i t e c t u r e   d e s i g n   d o c u m e n t . G r a c e f u l / n o n - g r a c e f u l   n o d e   s h u t d o w n . N o d e   a u t o s c a l i n g   t o   m a n a g e   t h e   n u m b e r   a n d   s i z e   o f   n o d e s   i n   y o u r   c l u s t e r . T a i n t s   a n d   T o l e r a t i o n s . N o d e   R e s o u r c e   M a n a g e r s . R e s o u r c e   M a n a g e m e n t   f o r   W i n d o w s   n o d e s .


Question: What is 2 - Communication between Nodes and the Control Plane?

Answer: T h i s   d o c u m e n t   c a t a l o g s   t h e   c o m m u n i c a t i o n   p a t h s   b e t w e e n   t h e   A P I   s e r v e r   a n d   t h e   K u b e r n e t e s   c l u s t e r .   T h e   i n t e n t   i s   t o   a l l o w   u s e r s   t o   c u s t o m i z e   t h e i r   i n s t a l l a t i o n   t o   h a r d e n   t h e   n e t w o r k   c o n f i g u r a t i o n   s u c h   t h a t   t h e   c l u s t e r   c a n   b e   r u n   o n   a n   u n t r u s t e d   n e t w o r k   ( o r   o n   f u l l y   p u b l i c   I P s   o n   a   c l o u d   p r o v i d e r ) .


Question: What is Node to Control Plane?

Answer: K u b e r n e t e s   h a s   a   " h u b - a n d - s p o k e "   A P I   p a t t e r n .   A l l   A P I   u s a g e   f r o m   n o d e s   ( o r   t h e   p o d s   t h e y   r u n )   t e r m i n a t e s   a t   t h e   A P I   s e r v e r .   N o n e   o f   t h e   o t h e r   c o n t r o l   p l a n e   c o m p o n e n t s   a r e   d e s i g n e d   t o   e x p o s e   r e m o t e   s e r v i c e s .   T h e   A P I   s e r v e r   i s   c o n f i g u r e d   t o   l i s t e n   f o r   r e m o t e   c o n n e c t i o n s   o n   a   s e c u r e   H T T P S   p o r t   ( t y p i c a l l y   4 4 3 )   w i t h   o n e   o r   m o r e   f o r m s   o f   c l i e n t   a u t h e n t i c a t i o n   e n a b l e d .   O n e   o r   m o r e   f o r m s   o f   a u t h o r i z a t i o n   s h o u l d   b e   e n a b l e d ,   e s p e c i a l l y   i f   a n o n y m o u s   r e q u e s t s   o r   s e r v i c e   a c c o u n t   t o k e n s   a r e   a l l o w e d .   N o d e s   s h o u l d   b e   p r o v i s i o n e d   w i t h   t h e   p u b l i c   r o o t   c e r t i f i c a t e   f o r   t h e   c l u s t e r   s u c h   t h a t   t h e y   c a n   c o n n e c t   s e c u r e l y   t o   t h e   A P I   s e r v e r   a l o n g   w i t h   v a l i d   c l i e n t   c r e d e n t i a l s .   A   g o o d   a p p r o a c h   i s   t h a t   t h e   c l i e n t   c r e d e n t i a l s   p r o v i d e d   t o   t h e   k u b e l e t   a r e   i n   t h e   f o r m   o f   a   c l i e n t   c e r t i f i c a t e .   S e e   k u b e l e t   T L S   b o o t s t r a p p i n g   f o r   a u t o m a t e d   p r o v i s i o n i n g   o f   k u b e l e t   c l i e n t   c e r t i f i c a t e s .   P o d s   t h a t   w i s h   t o   c o n n e c t   t o   t h e   A P I   s e r v e r   c a n   d o   s o   s e c u r e l y   b y   l e v e r a g i n g   a   s e r v i c e   a c c o u n t   s o   t h a t   K u b e r n e t e s   w i l l   a u t o m a t i c a l l y   i n j e c t


Question: What is Control plane to node?

Answer: T h e r e   a r e   t w o   p r i m a r y   c o m m u n i c a t i o n   p a t h s   f r o m   t h e   c o n t r o l   p l a n e   ( t h e   A P I   s e r v e r )   t o   t h e   n o d e s .   T h e   f i r s t   i s   f r o m   t h e   A P I   s e r v e r   t o   t h e   k u b e l e t   p r o c e s s   w h i c h   r u n s   o n   e a c h   n o d e   i n   t h e   c l u s t e r .   T h e   s e c o n d   i s   f r o m   t h e   A P I   s e r v e r   t o   a n y   n o d e ,   p o d ,   o r   s e r v i c e   t h r o u g h   t h e   A P I   s e r v e r ' s   p r o x y   f u n c t i o n a l i t y .


Question: What is API server to kubelet?

Answer: T h e   c o n n e c t i o n s   f r o m   t h e   A P I   s e r v e r   t o   t h e   k u b e l e t   a r e   u s e d   f o r :   F e t c h i n g   l o g s   f o r   p o d s . A t t a c h i n g   ( u s u a l l y   t h r o u g h   k u b e c t l )   t o   r u n n i n g   p o d s . P r o v i d i n g   t h e   k u b e l e t ' s   p o r t - f o r w a r d i n g   f u n c t i o n a l i t y .   T h e s e   c o n n e c t i o n s   t e r m i n a t e   a t   t h e   k u b e l e t ' s   H T T P S   e n d p o i n t .   B y   d e f a u l t ,   t h e   A P I   s e r v e r   d o e s   n o t   v e r i f y   t h e   k u b e l e t ' s   s e r v i n g   c e r t i f i c a t e ,   w h i c h   m a k e s   t h e   c o n n e c t i o n   s u b j e c t   t o   m a n - i n - t h e - m i d d l e   a t t a c k s   a n d   u n s a f e   t o   r u n   o v e r   u n t r u s t e d   a n d / o r   p u b l i c   n e t w o r k s .   T o   v e r i f y   t h i s   c o n n e c t i o n ,   u s e   t h e   - - k u b e l e t - c e r t i f i c a t e - a u t h o r i t y   f l a g   t o   p r o v i d e   t h e   A P I   s e r v e r   w i t h   a   r o o t   c e r t i f i c a t e   b u n d l e   t o   u s e   t o   v e r i f y   t h e   k u b e l e t ' s   s e r v i n g   c e r t i f i c a t e .   I f   t h a t   i s   n o t   p o s s i b l e ,   u s e   S S H   t u n n e l i n g   b e t w e e n   t h e   A P I   s e r v e r   a n d   k u b e l e t   i f   r e q u i r e d   t o   a v o i d   c o n n e c t i n g   o v e r   a n   u n t r u s t e d   o r   p u b l i c   n e t w o r k .   F i n a l l y ,   K u b e l e t   a u t h e n t i c a t i o n   a n d / o r   a u t h o r i z a t i o n   s h o u l d   b e   e n a b l e d   t o   s e c u r e   t h e   k u b e l e t   A P I .


Question: What is API server to nodes, pods, and services?

Answer: T h e   c o n n e c t i o n s   f r o m   t h e   A P I   s e r v e r   t o   a   n o d e ,   p o d ,   o r   s e r v i c e   d e f a u l t   t o   p l a i n   H T T P   c o n n e c t i o n s   a n d   a r e   t h e r e f o r e   n e i t h e r   a u t h e n t i c a t e d   n o r   e n c r y p t e d .   T h e y   c a n   b e   r u n   o v e r   a   s e c u r e   H T T P S   c o n n e c t i o n   b y   p r e f i x i n g   h t t p s :   t o   t h e   n o d e ,   p o d ,   o r   s e r v i c e   n a m e   i n   t h e   A P I   U R L ,   b u t   t h e y   w i l l   n o t   v a l i d a t e   t h e   c e r t i f i c a t e   p r o v i d e d   b y   t h e   H T T P S   e n d p o i n t   n o r   p r o v i d e   c l i e n t   c r e d e n t i a l s .   S o   w h i l e   t h e   c o n n e c t i o n   w i l l   b e   e n c r y p t e d ,   i t   w i l l   n o t   p r o v i d e   a n y   g u a r a n t e e s   o f   i n t e g r i t y .   T h e s e   c o n n e c t i o n s   a r e   n o t   c u r r e n t l y   s a f e   t o   r u n   o v e r   u n t r u s t e d   o r   p u b l i c   n e t w o r k s .


Question: What is SSH tunnels?

Answer: K u b e r n e t e s   s u p p o r t s   S S H   t u n n e l s   t o   p r o t e c t   t h e   c o n t r o l   p l a n e   t o   n o d e s   c o m m u n i c a t i o n   p a t h s .   I n   t h i s   c o n f i g u r a t i o n ,   t h e   A P I   s e r v e r   i n i t i a t e s   a n   S S H   t u n n e l   t o   e a c h   n o d e   i n   t h e   c l u s t e r   ( c o n n e c t i n g   t o   t h e   S S H   s e r v e r   l i s t e n i n g   o n   p o r t   2 2 )   a n d   p a s s e s   a l l   t r a f f i c   d e s t i n e d   f o r   a   k u b e l e t ,   n o d e ,   p o d ,   o r   s e r v i c e   t h r o u g h   t h e   t u n n e l .   T h i s   t u n n e l   e n s u r e s   t h a t   t h e   t r a f f i c   i s   n o t   e x p o s e d   o u t s i d e   o f   t h e   n e t w o r k   i n   w h i c h   t h e   n o d e s   a r e   r u n n i n g .


Question: What is Konnectivity service?

Answer: A s   a   r e p l a c e m e n t   t o   t h e   S S H   t u n n e l s ,   t h e   K o n n e c t i v i t y   s e r v i c e   p r o v i d e s   T C P   l e v e l   p r o x y   f o r   t h e   c o n t r o l   p l a n e   t o   c l u s t e r   c o m m u n i c a t i o n .   T h e   K o n n e c t i v i t y   s e r v i c e   c o n s i s t s   o f   t w o   p a r t s :   t h e   K o n n e c t i v i t y   s e r v e r   i n   t h e   c o n t r o l   p l a n e   n e t w o r k   a n d   t h e   K o n n e c t i v i t y   a g e n t s   i n   t h e   n o d e s   n e t w o r k .   T h e   K o n n e c t i v i t y   a g e n t s   i n i t i a t e   c o n n e c t i o n s   t o   t h e   K o n n e c t i v i t y   s e r v e r   a n d   m a i n t a i n   t h e   n e t w o r k   c o n n e c t i o n s .   A f t e r   e n a b l i n g   t h e   K o n n e c t i v i t y   s e r v i c e ,   a l l   c o n t r o l   p l a n e   t o   n o d e s   t r a f f i c   g o e s   t h r o u g h   t h e s e   c o n n e c t i o n s .   F o l l o w   t h e   K o n n e c t i v i t y   s e r v i c e   t a s k   t o   s e t   u p   t h e   K o n n e c t i v i t y   s e r v i c e   i n   y o u r   c l u s t e r .


Question: What is What's next?

Answer: R e a d   a b o u t   t h e   K u b e r n e t e s   c o n t r o l   p l a n e   c o m p o n e n t s L e a r n   m o r e   a b o u t   H u b s   a n d   S p o k e   m o d e l L e a r n   h o w   t o   S e c u r e   a   C l u s t e r L e a r n   m o r e   a b o u t   t h e   K u b e r n e t e s   A P I S e t   u p   K o n n e c t i v i t y   s e r v i c e U s e   P o r t   F o r w a r d i n g   t o   A c c e s s   A p p l i c a t i o n s   i n   a   C l u s t e r L e a r n   h o w   t o   F e t c h   l o g s   f o r   P o d s ,   u s e   k u b e c t l   p o r t - f o r w a r d


Question: What is 3 - Controllers?

Answer: I n   r o b o t i c s   a n d   a u t o m a t i o n ,   a   c o n t r o l   l o o p   i s   a   n o n - t e r m i n a t i n g   l o o p   t h a t   r e g u l a t e s   t h e   s t a t e   o f   a   s y s t e m .   H e r e   i s   o n e   e x a m p l e   o f   a   c o n t r o l   l o o p :   a   t h e r m o s t a t   i n   a   r o o m .   W h e n   y o u   s e t   t h e   t e m p e r a t u r e ,   t h a t ' s   t e l l i n g   t h e   t h e r m o s t a t   a b o u t   y o u r   d e s i r e d   s t a t e .   T h e   a c t u a l   r o o m   t e m p e r a t u r e   i s   t h e   c u r r e n t   s t a t e .   T h e   t h e r m o s t a t   a c t s   t o   b r i n g   t h e   c u r r e n t   s t a t e   c l o s e r   t o   t h e   d e s i r e d   s t a t e ,   b y   t u r n i n g   e q u i p m e n t   o n   o r   o f f .


Question: What is Controller pattern?

Answer: A   c o n t r o l l e r   t r a c k s   a t   l e a s t   o n e   K u b e r n e t e s   r e s o u r c e   t y p e .   T h e s e   o b j e c t s   h a v e   a   s p e c   f i e l d   t h a t   r e p r e s e n t s   t h e   d e s i r e d   s t a t e .   T h e   c o n t r o l l e r ( s )   f o r   t h a t   r e s o u r c e   a r e   r e s p o n s i b l e   f o r   m a k i n g   t h e   c u r r e n t   s t a t e   c o m e   c l o s e r   t o   t h a t   d e s i r e d   s t a t e .   T h e   c o n t r o l l e r   m i g h t   c a r r y   t h e   a c t i o n   o u t   i t s e l f ;   m o r e   c o m m o n l y ,   i n   K u b e r n e t e s ,   a   c o n t r o l l e r   w i l l   s e n d   m e s s a g e s   t o   t h e   A P I   s e r v e r   t h a t   h a v e   u s e f u l   s i d e   e f f e c t s .   Y o u ' l l   s e e   e x a m p l e s   o f   t h i s   b e l o w .


Question: What is Control via API server?

Answer: T h e   J o b   c o n t r o l l e r   i s   a n   e x a m p l e   o f   a   K u b e r n e t e s   b u i l t - i n   c o n t r o l l e r .   B u i l t - i n   c o n t r o l l e r s   m a n a g e   s t a t e   b y   i n t e r a c t i n g   w i t h   t h e   c l u s t e r   A P I   s e r v e r .   J o b   i s   a   K u b e r n e t e s   r e s o u r c e   t h a t   r u n s   a   P o d ,   o r   p e r h a p s   s e v e r a l   P o d s ,   t o   c a r r y   o u t   a   t a s k   a n d   t h e n   s t o p .   ( O n c e   s c h e d u l e d ,   P o d   o b j e c t s   b e c o m e   p a r t   o f   t h e   d e s i r e d   s t a t e   f o r   a   k u b e l e t ) .   W h e n   t h e   J o b   c o n t r o l l e r   s e e s   a   n e w   t a s k   i t   m a k e s   s u r e   t h a t ,   s o m e w h e r e   i n   y o u r   c l u s t e r ,   t h e   k u b e l e t s   o n   a   s e t   o f   N o d e s   a r e   r u n n i n g   t h e   r i g h t   n u m b e r   o f   P o d s   t o   g e t   t h e   w o r k   d o n e .   T h e   J o b   c o n t r o l l e r   d o e s   n o t   r u n   a n y   P o d s   o r   c o n t a i n e r s   i t s e l f .   I n s t e a d ,   t h e   J o b   c o n t r o l l e r   t e l l s   t h e   A P I   s e r v e r   t o   c r e a t e   o r   r e m o v e   P o d s .   O t h e r   c o m p o n e n t s   i n   t h e   c o n t r o l   p l a n e   a c t   o n   t h e   n e w   i n f o r m a t i o n   ( t h e r e   a r e   n e w   P o d s   t o   s c h e d u l e   a n d   r u n ) ,   a n d   e v e n t u a l l y   t h e   w o r k   i s   d o n e .   A f t e r   y o u   c r e a t e   a   n e w   J o b ,   t h e   d e s i r e d   s t a t e   i s   f o r   t h a t   J o b   t o   b e   c o m p l e t e d .   T h e   J o b   c o n t r o l l e r   m a k e s   t h e   c u r r e n t   s t a t e   f o r   t h a t   J o b   b e   n e a r e r   t o   y o u r   d e s i r e d   s t a t e :   c r e a t i n g   P o d s   t h a t   d o   t h e   w o r k   y o u   w a n t e d   f o r


Question: What is Direct control?

Answer: I n   c o n t r a s t   w i t h   J o b ,   s o m e   c o n t r o l l e r s   n e e d   t o   m a k e   c h a n g e s   t o   t h i n g s   o u t s i d e   o f   y o u r   c l u s t e r .   F o r   e x a m p l e ,   i f   y o u   u s e   a   c o n t r o l   l o o p   t o   m a k e   s u r e   t h e r e   a r e   e n o u g h   N o d e s   i n   y o u r   c l u s t e r ,   t h e n   t h a t   c o n t r o l l e r   n e e d s   s o m e t h i n g   o u t s i d e   t h e   c u r r e n t   c l u s t e r   t o   s e t   u p   n e w   N o d e s   w h e n   n e e d e d .   C o n t r o l l e r s   t h a t   i n t e r a c t   w i t h   e x t e r n a l   s t a t e   f i n d   t h e i r   d e s i r e d   s t a t e   f r o m   t h e   A P I   s e r v e r ,   t h e n   c o m m u n i c a t e   d i r e c t l y   w i t h   a n   e x t e r n a l   s y s t e m   t o   b r i n g   t h e   c u r r e n t   s t a t e   c l o s e r   i n   l i n e .   ( T h e r e   a c t u a l l y   i s   a   c o n t r o l l e r   t h a t   h o r i z o n t a l l y   s c a l e s   t h e   n o d e s   i n   y o u r   c l u s t e r . )   T h e   i m p o r t a n t   p o i n t   h e r e   i s   t h a t   t h e   c o n t r o l l e r   m a k e s   s o m e   c h a n g e s   t o   b r i n g   a b o u t   y o u r   d e s i r e d   s t a t e ,   a n d   t h e n   r e p o r t s   t h e   c u r r e n t   s t a t e   b a c k   t o   y o u r   c l u s t e r ' s   A P I   s e r v e r .   O t h e r   c o n t r o l   l o o p s   c a n   o b s e r v e   t h a t   r e p o r t e d   d a t a   a n d   t a k e   t h e i r   o w n   a c t i o n s .   I n   t h e   t h e r m o s t a t   e x a m p l e ,   i f   t h e   r o o m   i s   v e r y   c o l d   t h e n   a   d i f f e r e n t   c o n t r o l l e r   m i g h t   a l s o   t u r n   o n   a   f r o s t   p r o t e c t i o n   h e a t e r .   W i t h   K u b e r n e t e s   c l u s t e r s ,   t h e   c o n t r o l   p l a n e   i n d i r e c t l y   w o r k s   w i t h   I P


Question: What is Desired versus current state?

Answer: K u b e r n e t e s   t a k e s   a   c l o u d - n a t i v e   v i e w   o f   s y s t e m s ,   a n d   i s   a b l e   t o   h a n d l e   c o n s t a n t   c h a n g e .   Y o u r   c l u s t e r   c o u l d   b e   c h a n g i n g   a t   a n y   p o i n t   a s   w o r k   h a p p e n s   a n d   c o n t r o l   l o o p s   a u t o m a t i c a l l y   f i x   f a i l u r e s .   T h i s   m e a n s   t h a t ,   p o t e n t i a l l y ,   y o u r   c l u s t e r   n e v e r   r e a c h e s   a   s t a b l e   s t a t e .   A s   l o n g   a s   t h e   c o n t r o l l e r s   f o r   y o u r   c l u s t e r   a r e   r u n n i n g   a n d   a b l e   t o   m a k e   u s e f u l   c h a n g e s ,   i t   d o e s n ' t   m a t t e r   i f   t h e   o v e r a l l   s t a t e   i s   s t a b l e   o r   n o t .


Question: What is Design?

Answer: A s   a   t e n e t   o f   i t s   d e s i g n ,   K u b e r n e t e s   u s e s   l o t s   o f   c o n t r o l l e r s   t h a t   e a c h   m a n a g e   a   p a r t i c u l a r   a s p e c t   o f   c l u s t e r   s t a t e .   M o s t   c o m m o n l y ,   a   p a r t i c u l a r   c o n t r o l   l o o p   ( c o n t r o l l e r )   u s e s   o n e   k i n d   o f   r e s o u r c e   a s   i t s   d e s i r e d   s t a t e ,   a n d   h a s   a   d i f f e r e n t   k i n d   o f   r e s o u r c e   t h a t   i t   m a n a g e s   t o   m a k e   t h a t   d e s i r e d   s t a t e   h a p p e n .   F o r   e x a m p l e ,   a   c o n t r o l l e r   f o r   J o b s   t r a c k s   J o b   o b j e c t s   ( t o   d i s c o v e r   n e w   w o r k )   a n d   P o d   o b j e c t s   ( t o   r u n   t h e   J o b s ,   a n d   t h e n   t o   s e e   w h e n   t h e   w o r k   i s   f i n i s h e d ) .   I n   t h i s   c a s e   s o m e t h i n g   e l s e   c r e a t e s   t h e   J o b s ,   w h e r e a s   t h e   J o b   c o n t r o l l e r   c r e a t e s   P o d s .   I t ' s   u s e f u l   t o   h a v e   s i m p l e   c o n t r o l l e r s   r a t h e r   t h a n   o n e ,   m o n o l i t h i c   s e t   o f   c o n t r o l   l o o p s   t h a t   a r e   i n t e r l i n k e d .   C o n t r o l l e r s   c a n   f a i l ,   s o   K u b e r n e t e s   i s   d e s i g n e d   t o   a l l o w   f o r   t h a t .


Question: What is Note:?

Answer: T h e r e   c a n   b e   s e v e r a l   c o n t r o l l e r s   t h a t   c r e a t e   o r   u p d a t e   t h e   s a m e   k i n d   o f   o b j e c t .   B e h i n d   t h e   s c e n e s ,   K u b e r n e t e s   c o n t r o l l e r s   m a k e   s u r e   t h a t   t h e y   o n l y   p a y   a t t e n t i o n   t o   t h e   r e s o u r c e s   l i n k e d   t o   t h e i r   c o n t r o l l i n g   r e s o u r c e .   F o r   e x a m p l e ,   y o u   c a n   h a v e   D e p l o y m e n t s   a n d   J o b s ;   t h e s e   b o t h   c r e a t e   P o d s .   T h e   J o b   c o n t r o l l e r   d o e s   n o t   d e l e t e   t h e   P o d s   t h a t   y o u r   D e p l o y m e n t   c r e a t e d ,   b e c a u s e   t h e r e   i s   i n f o r m a t i o n   ( l a b e l s )   t h e   c o n t r o l l e r s   c a n   u s e   t o   t e l l   t h o s e   P o d s   a p a r t .


Question: What is Ways of running controllers?

Answer: K u b e r n e t e s   c o m e s   w i t h   a   s e t   o f   b u i l t - i n   c o n t r o l l e r s   t h a t   r u n   i n s i d e   t h e   k u b e - c o n t r o l l e r - m a n a g e r .   T h e s e   b u i l t - i n   c o n t r o l l e r s   p r o v i d e   i m p o r t a n t   c o r e   b e h a v i o r s .   T h e   D e p l o y m e n t   c o n t r o l l e r   a n d   J o b   c o n t r o l l e r   a r e   e x a m p l e s   o f   c o n t r o l l e r s   t h a t   c o m e   a s   p a r t   o f   K u b e r n e t e s   i t s e l f   ( " b u i l t - i n "   c o n t r o l l e r s ) .   K u b e r n e t e s   l e t s   y o u   r u n   a   r e s i l i e n t   c o n t r o l   p l a n e ,   s o   t h a t   i f   a n y   o f   t h e   b u i l t - i n   c o n t r o l l e r s   w e r e   t o   f a i l ,   a n o t h e r   p a r t   o f   t h e   c o n t r o l   p l a n e   w i l l   t a k e   o v e r   t h e   w o r k .   Y o u   c a n   f i n d   c o n t r o l l e r s   t h a t   r u n   o u t s i d e   t h e   c o n t r o l   p l a n e ,   t o   e x t e n d   K u b e r n e t e s .   O r ,   i f   y o u   w a n t ,   y o u   c a n   w r i t e   a   n e w   c o n t r o l l e r   y o u r s e l f .   Y o u   c a n   r u n   y o u r   o w n   c o n t r o l l e r   a s   a   s e t   o f   P o d s ,   o r   e x t e r n a l l y   t o   K u b e r n e t e s .   W h a t   f i t s   b e s t   w i l l   d e p e n d   o n   w h a t   t h a t   p a r t i c u l a r   c o n t r o l l e r   d o e s .


Question: What is What's next?

Answer: R e a d   a b o u t   t h e   K u b e r n e t e s   c o n t r o l   p l a n e D i s c o v e r   s o m e   o f   t h e   b a s i c   K u b e r n e t e s   o b j e c t s L e a r n   m o r e   a b o u t   t h e   K u b e r n e t e s   A P I I f   y o u   w a n t   t o   w r i t e   y o u r   o w n   c o n t r o l l e r ,   s e e   K u b e r n e t e s   e x t e n s i o n   p a t t e r n s   a n d   t h e   s a m p l e - c o n t r o l l e r   r e p o s i t o r y .


Question: What is 4 - Leases?

Answer: D i s t r i b u t e d   s y s t e m s   o f t e n   h a v e   a   n e e d   f o r   l e a s e s ,   w h i c h   p r o v i d e   a   m e c h a n i s m   t o   l o c k   s h a r e d   r e s o u r c e s   a n d   c o o r d i n a t e   a c t i v i t y   b e t w e e n   m e m b e r s   o f   a   s e t .   I n   K u b e r n e t e s ,   t h e   l e a s e   c o n c e p t   i s   r e p r e s e n t e d   b y   L e a s e   o b j e c t s   i n   t h e   c o o r d i n a t i o n . k 8 s . i o   A P I   G r o u p ,   w h i c h   a r e   u s e d   f o r   s y s t e m - c r i t i c a l   c a p a b i l i t i e s   s u c h   a s   n o d e   h e a r t b e a t s   a n d   c o m p o n e n t - l e v e l   l e a d e r   e l e c t i o n .


Question: What is Node heartbeats?

Answer: K u b e r n e t e s   u s e s   t h e   L e a s e   A P I   t o   c o m m u n i c a t e   k u b e l e t   n o d e   h e a r t b e a t s   t o   t h e   K u b e r n e t e s   A P I   s e r v e r .   F o r   e v e r y   N o d e   ,   t h e r e   i s   a   L e a s e   o b j e c t   w i t h   a   m a t c h i n g   n a m e   i n   t h e   k u b e - n o d e - l e a s e   n a m e s p a c e .   U n d e r   t h e   h o o d ,   e v e r y   k u b e l e t   h e a r t b e a t   i s   a n   u p d a t e   r e q u e s t   t o   t h i s   L e a s e   o b j e c t ,   u p d a t i n g   t h e   s p e c . r e n e w T i m e   f i e l d   f o r   t h e   L e a s e .   T h e   K u b e r n e t e s   c o n t r o l   p l a n e   u s e s   t h e   t i m e   s t a m p   o f   t h i s   f i e l d   t o   d e t e r m i n e   t h e   a v a i l a b i l i t y   o f   t h i s   N o d e .   S e e   N o d e   L e a s e   o b j e c t s   f o r   m o r e   d e t a i l s .


Question: What is Leader election?

Answer: K u b e r n e t e s   a l s o   u s e s   L e a s e s   t o   e n s u r e   o n l y   o n e   i n s t a n c e   o f   a   c o m p o n e n t   i s   r u n n i n g   a t   a n y   g i v e n   t i m e .   T h i s   i s   u s e d   b y   c o n t r o l   p l a n e   c o m p o n e n t s   l i k e   k u b e - c o n t r o l l e r - m a n a g e r   a n d   k u b e - s c h e d u l e r   i n   H A   c o n f i g u r a t i o n s ,   w h e r e   o n l y   o n e   i n s t a n c e   o f   t h e   c o m p o n e n t   s h o u l d   b e   a c t i v e l y   r u n n i n g   w h i l e   t h e   o t h e r   i n s t a n c e s   a r e   o n   s t a n d - b y .   R e a d   c o o r d i n a t e d   l e a d e r   e l e c t i o n   t o   l e a r n   a b o u t   h o w   K u b e r n e t e s   b u i l d s   o n   t h e   L e a s e   A P I   t o   s e l e c t   w h i c h   c o m p o n e n t   i n s t a n c e   a c t s   a s   l e a d e r .


Question: What is API server identity?

Answer: S t a r t i n g   i n   K u b e r n e t e s   v 1 . 2 6 ,   e a c h   k u b e - a p i s e r v e r   u s e s   t h e   L e a s e   A P I   t o   p u b l i s h   i t s   i d e n t i t y   t o   t h e   r e s t   o f   t h e   s y s t e m .   W h i l e   n o t   p a r t i c u l a r l y   u s e f u l   o n   i t s   o w n ,   t h i s   p r o v i d e s   a   m e c h a n i s m   f o r   c l i e n t s   t o   d i s c o v e r   h o w   m a n y   i n s t a n c e s   o f   k u b e - a p i s e r v e r   a r e   o p e r a t i n g   t h e   K u b e r n e t e s   c o n t r o l   p l a n e .   E x i s t e n c e   o f   k u b e - a p i s e r v e r   l e a s e s   e n a b l e s   f u t u r e   c a p a b i l i t i e s   t h a t   m a y   r e q u i r e   c o o r d i n a t i o n   b e t w e e n   e a c h   k u b e - a p i s e r v e r .   Y o u   c a n   i n s p e c t   L e a s e s   o w n e d   b y   e a c h   k u b e - a p i s e r v e r   b y   c h e c k i n g   f o r   l e a s e   o b j e c t s   i n   t h e   k u b e - s y s t e m   n a m e s p a c e   w i t h   t h e   n a m e   a p i s e r v e r - < s h a 2 5 6 - h a s h > .   A l t e r n a t i v e l y   y o u   c a n   u s e   t h e   l a b e l   s e l e c t o r   a p i s e r v e r . k u b e r n e t e s . i o / i d e n t i t y = k u b e - a p i s e r v e r :   k u b e c t l   - n   k u b e - s y s t e m   g e t   l e a s e   - l   a p i s e r v e r . k u b e r n e t e s . i o / i d e n t i t y = k u b e - a p i s e r v e r   N A M E   H O L D E R   A G E   a p i s e r v e r - 0 7 a 5 e a 9 b 9 b 0 7 2 c 4 a 5 f 3 d 1 c 3 7 0 2   a p i s e r v e r - 0 7 a 5 e a 9 b 9 b 0 7 2 c 4 a 5 f 3 d 1 c 3 7 0 2 _ 0 c 8 9 1 4 f 7 - 0 f 3 5 - 4 4 0 e - 8 6 7 6 - 7 8 4 4 9 7 7 d 3 a 0 5   5 m 3 3 s   a p i s e r v e r - 7 b e 9 e 0 6 1 c 5 9 d 3 6 8 b 3 d d a f 1 3 7 6 e   a p i s e r v e r - 7 b e 9 e 0 6 1 c 5 9 d 3 6 8 b 3 d d a f 1 3 7 6 e _ 8 4 f 2 a 8 5 d - 3 7 c 1 - 4 b 1 4 - b 6 b 9 - 6 0 3 e 6 2 e 4 8 9 6 f   4 m 2 3 s   a p i s e r v


Question: What is Workloads?

Answer: Y o u r   o w n   w o r k l o a d   c a n   d e f i n e   i t s   o w n   u s e   o f   L e a s e s .   F o r   e x a m p l e ,   y o u   m i g h t   r u n   a   c u s t o m   c o n t r o l l e r   w h e r e   a   p r i m a r y   o r   l e a d e r   m e m b e r   p e r f o r m s   o p e r a t i o n s   t h a t   i t s   p e e r s   d o   n o t .   Y o u   d e f i n e   a   L e a s e   s o   t h a t   t h e   c o n t r o l l e r   r e p l i c a s   c a n   s e l e c t   o r   e l e c t   a   l e a d e r ,   u s i n g   t h e   K u b e r n e t e s   A P I   f o r   c o o r d i n a t i o n .   I f   y o u   d o   u s e   a   L e a s e ,   i t ' s   a   g o o d   p r a c t i c e   t o   d e f i n e   a   n a m e   f o r   t h e   L e a s e   t h a t   i s   o b v i o u s l y   l i n k e d   t o   t h e   p r o d u c t   o r   c o m p o n e n t .   F o r   e x a m p l e ,   i f   y o u   h a v e   a   c o m p o n e n t   n a m e d   E x a m p l e   F o o ,   u s e   a   L e a s e   n a m e d   e x a m p l e - f o o .   I f   a   c l u s t e r   o p e r a t o r   o r   a n o t h e r   e n d   u s e r   c o u l d   d e p l o y   m u l t i p l e   i n s t a n c e s   o f   a   c o m p o n e n t ,   s e l e c t   a   n a m e   p r e f i x   a n d   p i c k   a   m e c h a n i s m   ( s u c h   a s   h a s h   o f   t h e   n a m e   o f   t h e   D e p l o y m e n t )   t o   a v o i d   n a m e   c o l l i s i o n s   f o r   t h e   L e a s e s .   Y o u   c a n   u s e   a n o t h e r   a p p r o a c h   s o   l o n g   a s   i t   a c h i e v e s   t h e   s a m e   o u t c o m e :   d i f f e r e n t   s o f t w a r e   p r o d u c t s   d o   n o t   c o n f l i c t   w i t h   o n e   a n o t h e r .


Question: What is 5 - Cloud Controller Manager?

Answer: C l o u d   i n f r a s t r u c t u r e   t e c h n o l o g i e s   l e t   y o u   r u n   K u b e r n e t e s   o n   p u b l i c ,   p r i v a t e ,   a n d   h y b r i d   c l o u d s .   K u b e r n e t e s   b e l i e v e s   i n   a u t o m a t e d ,   A P I - d r i v e n   i n f r a s t r u c t u r e   w i t h o u t   t i g h t   c o u p l i n g   b e t w e e n   c o m p o n e n t s .   T h e   c l o u d - c o n t r o l l e r - m a n a g e r   i s   a   K u b e r n e t e s   c o n t r o l   p l a n e   c o m p o n e n t   t h a t   e m b e d s   c l o u d - s p e c i f i c   c o n t r o l   l o g i c .   T h e   c l o u d   c o n t r o l l e r   m a n a g e r   l e t s   y o u   l i n k   y o u r   c l u s t e r   i n t o   y o u r   c l o u d   p r o v i d e r ' s   A P I ,   a n d   s e p a r a t e s   o u t   t h e   c o m p o n e n t s   t h a t   i n t e r a c t   w i t h   t h a t   c l o u d   p l a t f o r m   f r o m   c o m p o n e n t s   t h a t   o n l y   i n t e r a c t   w i t h   y o u r   c l u s t e r .   T h e   c l o u d - c o n t r o l l e r - m a n a g e r   i s   a   K u b e r n e t e s   c o n t r o l   p l a n e   c o m p o n e n t   t h a t   e m b e d s   c l o u d - s p e c i f i c   c o n t r o l   l o g i c .   T h e   c l o u d   c o n t r o l l e r   m a n a g e r   l e t s   y o u   l i n k   y o u r   c l u s t e r   i n t o   y o u r   c l o u d   p r o v i d e r ' s   A P I ,   a n d   s e p a r a t e s   o u t   t h e   c o m p o n e n t s   t h a t   i n t e r a c t   w i t h   t h a t   c l o u d   p l a t f o r m   f r o m   c o m p o n e n t s   t h a t   o n l y   i n t e r a c t   w i t h   y o u r   c l u s t e r .   B y   d e c o u p l i n g   t h e   i n t e r o p e r a b i l i t y   l o g i c   b e t w e e n   K u b e r n e t e s   a n d   t h e   u n d e r l y i n g   c l o u d   i n f r a s t r u c t u r e ,   t h e   c l o u d - c o n t r o l l e r - m a n a g e r   c o m p o n e n t   e n a b l e s   c l o


Question: What is Design?

Answer: T h e   c l o u d   c o n t r o l l e r   m a n a g e r   r u n s   i n   t h e   c o n t r o l   p l a n e   a s   a   r e p l i c a t e d   s e t   o f   p r o c e s s e s   ( u s u a l l y ,   t h e s e   a r e   c o n t a i n e r s   i n   P o d s ) .   E a c h   c l o u d - c o n t r o l l e r - m a n a g e r   i m p l e m e n t s   m u l t i p l e   c o n t r o l l e r s   i n   a   s i n g l e   p r o c e s s .


Question: What is Cloud controller manager functions?

Answer: T h e   c o n t r o l l e r s   i n s i d e   t h e   c l o u d   c o n t r o l l e r   m a n a g e r   i n c l u d e :


Question: What is Node controller?

Answer: T h e   n o d e   c o n t r o l l e r   i s   r e s p o n s i b l e   f o r   u p d a t i n g   N o d e   o b j e c t s   w h e n   n e w   s e r v e r s   a r e   c r e a t e d   i n   y o u r   c l o u d   i n f r a s t r u c t u r e .   T h e   n o d e   c o n t r o l l e r   o b t a i n s   i n f o r m a t i o n   a b o u t   t h e   h o s t s   r u n n i n g   i n s i d e   y o u r   t e n a n c y   w i t h   t h e   c l o u d   p r o v i d e r .   T h e   n o d e   c o n t r o l l e r   p e r f o r m s   t h e   f o l l o w i n g   f u n c t i o n s :   U p d a t e   a   N o d e   o b j e c t   w i t h   t h e   c o r r e s p o n d i n g   s e r v e r ' s   u n i q u e   i d e n t i f i e r   o b t a i n e d   f r o m   t h e   c l o u d   p r o v i d e r   A P I . A n n o t a t i n g   a n d   l a b e l l i n g   t h e   N o d e   o b j e c t   w i t h   c l o u d - s p e c i f i c   i n f o r m a t i o n ,   s u c h   a s   t h e   r e g i o n   t h e   n o d e   i s   d e p l o y e d   i n t o   a n d   t h e   r e s o u r c e s   ( C P U ,   m e m o r y ,   e t c )   t h a t   i t   h a s   a v a i l a b l e . O b t a i n   t h e   n o d e ' s   h o s t n a m e   a n d   n e t w o r k   a d d r e s s e s . V e r i f y i n g   t h e   n o d e ' s   h e a l t h .   I n   c a s e   a   n o d e   b e c o m e s   u n r e s p o n s i v e ,   t h i s   c o n t r o l l e r   c h e c k s   w i t h   y o u r   c l o u d   p r o v i d e r ' s   A P I   t o   s e e   i f   t h e   s e r v e r   h a s   b e e n   d e a c t i v a t e d   /   d e l e t e d   /   t e r m i n a t e d .   I f   t h e   n o d e   h a s   b e e n   d e l e t e d   f r o m   t h e   c l o u d ,   t h e   c o n t r o l l e r   d e l e t e s   t h e   N o d e   o b j e c t   f r o m   y o u r   K u b e r n e t e s   c l u s t e r .   S o m e   c l o u d   p r o v i d e r   i m p l e m e n t a t i o n s   s p l i t   t h i s   i n t o   a   n o d e   c o n t r o l l e r   a n d   a   s e p a r a


Question: What is Route controller?

Answer: T h e   r o u t e   c o n t r o l l e r   i s   r e s p o n s i b l e   f o r   c o n f i g u r i n g   r o u t e s   i n   t h e   c l o u d   a p p r o p r i a t e l y   s o   t h a t   c o n t a i n e r s   o n   d i f f e r e n t   n o d e s   i n   y o u r   K u b e r n e t e s   c l u s t e r   c a n   c o m m u n i c a t e   w i t h   e a c h   o t h e r .   D e p e n d i n g   o n   t h e   c l o u d   p r o v i d e r ,   t h e   r o u t e   c o n t r o l l e r   m i g h t   a l s o   a l l o c a t e   b l o c k s   o f   I P   a d d r e s s e s   f o r   t h e   P o d   n e t w o r k .


Question: What is Service controller?

Answer: S e r v i c e s   i n t e g r a t e   w i t h   c l o u d   i n f r a s t r u c t u r e   c o m p o n e n t s   s u c h   a s   m a n a g e d   l o a d   b a l a n c e r s ,   I P   a d d r e s s e s ,   n e t w o r k   p a c k e t   f i l t e r i n g ,   a n d   t a r g e t   h e a l t h   c h e c k i n g .   T h e   s e r v i c e   c o n t r o l l e r   i n t e r a c t s   w i t h   y o u r   c l o u d   p r o v i d e r ' s   A P I s   t o   s e t   u p   l o a d   b a l a n c e r s   a n d   o t h e r   i n f r a s t r u c t u r e   c o m p o n e n t s   w h e n   y o u   d e c l a r e   a   S e r v i c e   r e s o u r c e   t h a t   r e q u i r e s   t h e m .


Question: What is Authorization?

Answer: T h i s   s e c t i o n   b r e a k s   d o w n   t h e   a c c e s s   t h a t   t h e   c l o u d   c o n t r o l l e r   m a n a g e r   r e q u i r e s   o n   v a r i o u s   A P I   o b j e c t s ,   i n   o r d e r   t o   p e r f o r m   i t s   o p e r a t i o n s .


Question: What is Node controller?

Answer: T h e   N o d e   c o n t r o l l e r   o n l y   w o r k s   w i t h   N o d e   o b j e c t s .   I t   r e q u i r e s   f u l l   a c c e s s   t o   r e a d   a n d   m o d i f y   N o d e   o b j e c t s .   v 1 / N o d e :   g e t l i s t c r e a t e u p d a t e p a t c h w a t c h d e l e t e


Question: What is Route controller?

Answer: T h e   r o u t e   c o n t r o l l e r   l i s t e n s   t o   N o d e   o b j e c t   c r e a t i o n   a n d   c o n f i g u r e s   r o u t e s   a p p r o p r i a t e l y .   I t   r e q u i r e s   G e t   a c c e s s   t o   N o d e   o b j e c t s .   v 1 / N o d e :   g e t


Question: What is Service controller?

Answer: T h e   s e r v i c e   c o n t r o l l e r   w a t c h e s   f o r   S e r v i c e   o b j e c t   c r e a t e ,   u p d a t e   a n d   d e l e t e   e v e n t s   a n d   t h e n   c o n f i g u r e s   l o a d   b a l a n c e r s   f o r   t h o s e   S e r v i c e s   a p p r o p r i a t e l y .   T o   a c c e s s   S e r v i c e s ,   i t   r e q u i r e s   l i s t ,   a n d   w a t c h   a c c e s s .   T o   u p d a t e   S e r v i c e s ,   i t   r e q u i r e s   p a t c h   a n d   u p d a t e   a c c e s s   t o   t h e   s t a t u s   s u b r e s o u r c e .   v 1 / S e r v i c e :   l i s t g e t w a t c h p a t c h u p d a t e


Question: What is Others?

Answer: T h e   i m p l e m e n t a t i o n   o f   t h e   c o r e   o f   t h e   c l o u d   c o n t r o l l e r   m a n a g e r   r e q u i r e s   a c c e s s   t o   c r e a t e   E v e n t   o b j e c t s ,   a n d   t o   e n s u r e   s e c u r e   o p e r a t i o n ,   i t   r e q u i r e s   a c c e s s   t o   c r e a t e   S e r v i c e A c c o u n t s .   v 1 / E v e n t :   c r e a t e p a t c h u p d a t e   v 1 / S e r v i c e A c c o u n t :   c r e a t e   T h e   R B A C   C l u s t e r R o l e   f o r   t h e   c l o u d   c o n t r o l l e r   m a n a g e r   l o o k s   l i k e :   a p i V e r s i o n :   r b a c . a u t h o r i z a t i o n . k 8 s . i o / v 1   k i n d :   C l u s t e r R o l e   m e t a d a t a :   n a m e :   c l o u d - c o n t r o l l e r - m a n a g e r   r u l e s :   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   e v e n t s   v e r b s :   -   c r e a t e   -   p a t c h   -   u p d a t e   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   n o d e s   v e r b s :   -   ' * '   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   n o d e s / s t a t u s   v e r b s :   -   p a t c h   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   s e r v i c e s   v e r b s :   -   l i s t   -   w a t c h   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   s e r v i c e s / s t a t u s   v e r b s :   -   p a t c h   -   u p d a t e   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   s e r v i c e a c c o u n t s   v e r b s :   -   c r e a t e   -   a p i G r o u p s :   -   " "   r e s o u r c e s :   -   p e r s i s t e n t v o l u m e s   v e r b s :   -   g e t   -   l i s t   -   u p d a t e   -   w a t c h


Question: What is What's next?

Answer: C l o u d   C o n t r o l l e r   M a n a g e r   A d m i n i s t r a t i o n   h a s   i n s t r u c t i o n s   o n   r u n n i n g   a n d   m a n a g i n g   t h e   c l o u d   c o n t r o l l e r   m a n a g e r . T o   u p g r a d e   a   H A   c o n t r o l   p l a n e   t o   u s e   t h e   c l o u d   c o n t r o l l e r   m a n a g e r ,   s e e   M i g r a t e   R e p l i c a t e d   C o n t r o l   P l a n e   T o   U s e   C l o u d   C o n t r o l l e r   M a n a g e r . W a n t   t o   k n o w   h o w   t o   i m p l e m e n t   y o u r   o w n   c l o u d   c o n t r o l l e r   m a n a g e r ,   o r   e x t e n d   a n   e x i s t i n g   p r o j e c t ? T h e   c l o u d   c o n t r o l l e r   m a n a g e r   u s e s   G o   i n t e r f a c e s ,   s p e c i f i c a l l y ,   C l o u d P r o v i d e r   i n t e r f a c e   d e f i n e d   i n   c l o u d . g o   f r o m   k u b e r n e t e s / c l o u d - p r o v i d e r   t o   a l l o w   i m p l e m e n t a t i o n s   f r o m   a n y   c l o u d   t o   b e   p l u g g e d   i n . T h e   i m p l e m e n t a t i o n   o f   t h e   s h a r e d   c o n t r o l l e r s   h i g h l i g h t e d   i n   t h i s   d o c u m e n t   ( N o d e ,   R o u t e ,   a n d   S e r v i c e ) ,   a n d   s o m e   s c a f f o l d i n g   a l o n g   w i t h   t h e   s h a r e d   c l o u d p r o v i d e r   i n t e r f a c e ,   i s   p a r t   o f   t h e   K u b e r n e t e s   c o r e .   I m p l e m e n t a t i o n s   s p e c i f i c   t o   c l o u d   p r o v i d e r s   a r e   o u t s i d e   t h e   c o r e   o f   K u b e r n e t e s   a n d   i m p l e m e n t   t h e   C l o u d P r o v i d e r   i n t e r f a c e . F o r   m o r e   i n f o r m a t i o n   a b o u t   d e v e l o p i n g   p l u g i n s ,   s e e   D e v e l o p i n g   C l o u d   C o n t r o l l e r   M a n a g e r .   C l o u d   C o n t r o l l e r   M a n a g e r   A d m i n i s t r a t i o n   h a s   i n s t r u c t i


Question: What is 6 - About cgroup v2?

Answer: O n   L i n u x ,   c o n t r o l   g r o u p s   c o n s t r a i n   r e s o u r c e s   t h a t   a r e   a l l o c a t e d   t o   p r o c e s s e s .   T h e   k u b e l e t   a n d   t h e   u n d e r l y i n g   c o n t a i n e r   r u n t i m e   n e e d   t o   i n t e r f a c e   w i t h   c g r o u p s   t o   e n f o r c e   r e s o u r c e   m a n a g e m e n t   f o r   p o d s   a n d   c o n t a i n e r s   w h i c h   i n c l u d e s   c p u / m e m o r y   r e q u e s t s   a n d   l i m i t s   f o r   c o n t a i n e r i z e d   w o r k l o a d s .   T h e r e   a r e   t w o   v e r s i o n s   o f   c g r o u p s   i n   L i n u x :   c g r o u p   v 1   a n d   c g r o u p   v 2 .   c g r o u p   v 2   i s   t h e   n e w   g e n e r a t i o n   o f   t h e   c g r o u p   A P I .


Question: What is What is cgroup v2??

Answer: c g r o u p   v 2   i s   t h e   n e x t   v e r s i o n   o f   t h e   L i n u x   c g r o u p   A P I .   c g r o u p   v 2   p r o v i d e s   a   u n i f i e d   c o n t r o l   s y s t e m   w i t h   e n h a n c e d   r e s o u r c e   m a n a g e m e n t   c a p a b i l i t i e s .   c g r o u p   v 2   o f f e r s   s e v e r a l   i m p r o v e m e n t s   o v e r   c g r o u p   v 1 ,   s u c h   a s   t h e   f o l l o w i n g :   S i n g l e   u n i f i e d   h i e r a r c h y   d e s i g n   i n   A P I S a f e r   s u b - t r e e   d e l e g a t i o n   t o   c o n t a i n e r s N e w e r   f e a t u r e s   l i k e   P r e s s u r e   S t a l l   I n f o r m a t i o n E n h a n c e d   r e s o u r c e   a l l o c a t i o n   m a n a g e m e n t   a n d   i s o l a t i o n   a c r o s s   m u l t i p l e   r e s o u r c e s U n i f i e d   a c c o u n t i n g   f o r   d i f f e r e n t   t y p e s   o f   m e m o r y   a l l o c a t i o n s   ( n e t w o r k   m e m o r y ,   k e r n e l   m e m o r y ,   e t c ) A c c o u n t i n g   f o r   n o n - i m m e d i a t e   r e s o u r c e   c h a n g e s   s u c h   a s   p a g e   c a c h e   w r i t e   b a c k s   U n i f i e d   a c c o u n t i n g   f o r   d i f f e r e n t   t y p e s   o f   m e m o r y   a l l o c a t i o n s   ( n e t w o r k   m e m o r y ,   k e r n e l   m e m o r y ,   e t c ) A c c o u n t i n g   f o r   n o n - i m m e d i a t e   r e s o u r c e   c h a n g e s   s u c h   a s   p a g e   c a c h e   w r i t e   b a c k s   S o m e   K u b e r n e t e s   f e a t u r e s   e x c l u s i v e l y   u s e   c g r o u p   v 2   f o r   e n h a n c e d   r e s o u r c e   m a n a g e m e n t   a n d   i s o l a t i o n .   F o r   e x a m p l e ,   t h e   M e m o r y Q o S   f e a t u r e   i m p r o v e s   m e m o r y   Q o S   a n d   r e l i e s   o n   c g r o u p   v 2   p r i m i t i v e s .


Question: What is Using cgroup v2?

Answer: T h e   r e c o m m e n d e d   w a y   t o   u s e   c g r o u p   v 2   i s   t o   u s e   a   L i n u x   d i s t r i b u t i o n   t h a t   e n a b l e s   a n d   u s e s   c g r o u p   v 2   b y   d e f a u l t .   T o   c h e c k   i f   y o u r   d i s t r i b u t i o n   u s e s   c g r o u p   v 2 ,   r e f e r   t o   I d e n t i f y   c g r o u p   v e r s i o n   o n   L i n u x   n o d e s .


Question: What is Requirements?

Answer: c g r o u p   v 2   h a s   t h e   f o l l o w i n g   r e q u i r e m e n t s :   O S   d i s t r i b u t i o n   e n a b l e s   c g r o u p   v 2 L i n u x   K e r n e l   v e r s i o n   i s   5 . 8   o r   l a t e r C o n t a i n e r   r u n t i m e   s u p p o r t s   c g r o u p   v 2 .   F o r   e x a m p l e : c o n t a i n e r d   v 1 . 4   a n d   l a t e r c r i - o   v 1 . 2 0   a n d   l a t e r T h e   k u b e l e t   a n d   t h e   c o n t a i n e r   r u n t i m e   a r e   c o n f i g u r e d   t o   u s e   t h e   s y s t e m d   c g r o u p   d r i v e r   c o n t a i n e r d   v 1 . 4   a n d   l a t e r c r i - o   v 1 . 2 0   a n d   l a t e r


Question: What is Linux Distribution cgroup v2 support?

Answer: F o r   a   l i s t   o f   L i n u x   d i s t r i b u t i o n s   t h a t   u s e   c g r o u p   v 2 ,   r e f e r   t o   t h e   c g r o u p   v 2   d o c u m e n t a t i o n   C o n t a i n e r   O p t i m i z e d   O S   ( s i n c e   M 9 7 ) U b u n t u   ( s i n c e   2 1 . 1 0 ,   2 2 . 0 4 +   r e c o m m e n d e d ) D e b i a n   G N U / L i n u x   ( s i n c e   D e b i a n   1 1   b u l l s e y e ) F e d o r a   ( s i n c e   3 1 ) A r c h   L i n u x   ( s i n c e   A p r i l   2 0 2 1 ) R H E L   a n d   R H E L - l i k e   d i s t r i b u t i o n s   ( s i n c e   9 )   T o   c h e c k   i f   y o u r   d i s t r i b u t i o n   i s   u s i n g   c g r o u p   v 2 ,   r e f e r   t o   y o u r   d i s t r i b u t i o n ' s   d o c u m e n t a t i o n   o r   f o l l o w   t h e   i n s t r u c t i o n s   i n   I d e n t i f y   t h e   c g r o u p   v e r s i o n   o n   L i n u x   n o d e s .   Y o u   c a n   a l s o   e n a b l e   c g r o u p   v 2   m a n u a l l y   o n   y o u r   L i n u x   d i s t r i b u t i o n   b y   m o d i f y i n g   t h e   k e r n e l   c m d l i n e   b o o t   a r g u m e n t s .   I f   y o u r   d i s t r i b u t i o n   u s e s   G R U B ,   s y s t e m d . u n i f i e d _ c g r o u p _ h i e r a r c h y = 1   s h o u l d   b e   a d d e d   i n   G R U B _ C M D L I N E _ L I N U X   u n d e r   / e t c / d e f a u l t / g r u b ,   f o l l o w e d   b y   s u d o   u p d a t e - g r u b .   H o w e v e r ,   t h e   r e c o m m e n d e d   a p p r o a c h   i s   t o   u s e   a   d i s t r i b u t i o n   t h a t   a l r e a d y   e n a b l e s   c g r o u p   v 2   b y   d e f a u l t .