Docker Redhat 8

2/13/2022by admin

Kubernetes is an open source container orchestration tool for deploying applications. In Kubernetes cluster setup, we have one master and multiple worker nodes or Minion. From the master node, we manage the cluster and its nodes using kubeadm and kubectl utility. In CentOS 8/RHEL 8. docker has now been replaced by podman and buildah tools from Redhat. So docker package has been removed from the default package repository. In this guide, we will learnt how to Install and configure Kubernetes Cluster (k8s) on CentOS 8/RHEL 8.

  1. Docker Red Hat 8th
  2. Redhat 8 Docker Install
  3. Docker And Redhat 8
  4. Docker Rhel 8.3
  • 1.2 Convert.pem files to.pkk for putty. 2 Install Docker on Red Hat Enterprise Linux AWS EC2. 2.1 Step 1 – Check Linux version. 2.2 Step 2 – Update yum. 2.3 Step 3 – Add Docker Repository. 3 Step 4 – Install Docker Engine. 3.1 Step 5 – Enable Docker Service. 3.2 Step 6 – Start Docker. 3.3 Step 7- Verify Docker is Running.
  • The list returned depends on which repositories are enabled, and is specific to your version of RHEL (indicated by the.el8 suffix in this example). Install a specific version by its fully qualified package name, which is the package name (docker-ce) plus the version string (2nd column) starting at the first colon (:), up to the first hyphen, separated by a hyphen (-).

Kubernetes can be installed and deployed on various platforms using following methods,

  • Minikube ( single node kubernetes cluster)
  • Kops ( Multi node kubernetes setup on AWS )
  • Kubeadm ( On-premise Multi Node kubernetes Cluster )

Prerequisite

Install the Docker package. Dnf install docker-ce docker-ce-cli containerd.io. Start the Docker service and add it to autorun. Systemctl enable -now docker. CentOS 8 uses a firewall other than Docker. Hence, if you have firewalld enabled, you need to add a masquerade rule to it. Firewall-cmd -zone=public -add-masquerade -permanent.

  • Swap should be disabled in order to run “kubeadm init“ command. Disable Swap in all nodes using “swapoff -a” command and remove or comment out swap partitions from fstab file.
  • Three machines running CentOS 8 – 1 Master Node and 2 Worker Nodes.
  • It is recommended to have at least 2 CPUs with 2GB RAM or more per machine.
  • All nodes should be able to connect to one another, either on a private or public network.
  • Root or sudo user privileges required.
  • br_netfilter module should be enabled on all machines.

Read Also :Kubernetes Tutorial – Advanced Overview of K8s

Installing and Configuring Kubernetes Cluster on CentOS 8/RHEL 8

We require multiple machines to form a cluster in kubernetes where one or more machine can be master which controls the cluster and one or more machine can be worker nodes where pods resides and used to deploy applications.

The following instructions will be performed on centos 8 in order to establish Kubernetes cluster.

Setup hostname, disable SELinux & configure firewall rules

Login to kubernetes master node and disable selinux first using below commands. in below configuration file, make SELinux permissive from enforcing and then reboot the machine.

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Next setup the following firewall rules.

Now load the br_netfilter module,

Setup Docker-CE and Kubernetes Repositories

Here, you need to add the docker repository in the default package using the below dnf config-manager command.

Next, install containerd.io package which is available as a daemon that will manages the complete container lifecycle,

Afterwards, you need to add Kubernetes repositories manually as they don’t come installed by default on CentOS 8.

Install Docker-CE

Next install the current supportable version of docker-ce package.

Now you can install docker-compose,

You should enable and start the docker service now.

Install Kubernetes

Kubeadm helps you bootstrap a minimum viable Kubernetes cluster that confirms the best practice. Kubeadm also supports other cluster lifecycle functions, such as upgrades, downgrade, and managing bootstrap tokens. Kubeadm is also integration-friendly with other orchestration tools like Ansible and Terraform.

With the package repo now ready, you can go ahead and install kubeadm package.

When the installation finishes successfully, enable and start the service.

Swap must disabled in order to run kubelet command,

Kubernetes master acts as the control plane for the cluster runs a few critical services necessary for the cluster. As such, the initialization process will do a series of prechecks to ensure that the machine is ready to run Kubernetes. These prechecks expose warnings and exit on errors. kubeadm init then downloads and installs the cluster control plane components.

Initialization of kubernetes master is a completely automated process that is controlled by the “kubeadm init“ command as shown.

Once Kubernetes initialized successfully, you must enable your user to start using the cluster. In our scenario, we will be using the root user. You can also start the cluster using sudo user as shown.

Now you have to enable Kubernetes cluster and use flannel to get the config in yaml. And this should be running only on Master node,

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Now confirm that the kubectl command is activated.

Initially you will see the status of the master node is “NotReady”. This is because we are yet to deploy the pod network to the cluster. The pod Network is the overlay network for the cluster, that is deployed on top of the present node network. It is designed to allow connectivity across the pod.

Conclusion

In this guide you saw how to how to Install and configure Kubernetes Cluster (k8s) on CentOS 8/RHEL 8. Please feel free to ask any questions or queries in comment box below.

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Read Also :How to Install Docker Engine on Ubuntu 18.04/20.04

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Docker Rhel 8.3

Read Also :Docker Tutorial – An Advanced Overview of Docker

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