Creating a kubernetes cluster

On June 3, 2019June 3, 2019 By Aryan NavaIn Docker, kubernetesLeave a comment

How to create kubernetes cluster?

Get three EC2 instances from AWS and start the following steps.

The first thing that we are going to do is use SSH to log in to all machines. Once we have logged in, we need to elevate privileges using sudo.
```
sudo su  
```

Disable SELinux.

setenforce 0
sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux

Enable the br_netfilter module for cluster communication.

modprobe br_netfilter
echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

Ensure that the Docker dependencies are satisfied.

yum install -y yum-utils device-mapper-persistent-data lvm2

Add the Docker repo and install Docker.

yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
yum install -y docker-ce

Set the cgroup driver for Docker to systemd, then reload systemd, enable and start Docker

sed -i '/^ExecStart/ s/$/ --exec-opt native.cgroupdriver=systemd/' /usr/lib/systemd/system/docker.service
systemctl daemon-reload
systemctl enable docker --now

Add the repo for Kubernetes.

cat << EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
EOF

Install Kubernetes.
```
yum install -y kubelet kubeadm kubectl
```
Enable the kubelet service. The kubelet service will fail to start until the cluster is initialized, this is expected.
```
systemctl enable kubelet
```

*Note: Complete the following section on the MASTER ONLY!

Initialize the cluster using the IP range for Flannel.
```
kubeadm init --pod-network-cidr=10.244.0.0/16
```
Copy the kubeadmn join command that is in the output. We will need this later.

Exit sudo and copy the admin.conf to your home directory and take ownership.

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Deploy Flannel.

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Check the cluster state.
```
kubectl get pods --all-namespaces
```
Note: Complete the following steps on the NODES ONLY!
Run the join command that you copied earlier, this requires running the command as sudo on the nodes. Then check your nodes from the master.
```
kubectl get nodes
```

Create and scale a deployment using kubectl.keyboard_arrow_up

Create a simple deployment.

kubectl create deployment nginx --image=nginx

Inspect the pod.
```
kubectl get pods
```

Scale the deployment.

kubectl scale deployment nginx --replicas=4

Inspect the pods. You should now have 4.
```
kubectl get pods
```

Building a Kubernetes Cluster with Kubeadm

On June 3, 2019June 3, 2019 By Aryan NavaIn Docker, kubernetesLeave a comment

To build a cluster, you need to have master and slave nodes and dockers need to be installed.

1. Install Docker on all three nodes.keyboard_arrow_up

Do the following on all three nodes:

apt install gpg-agent


curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository \
"deb [arch=amd64] https://download.docker.com/linux/ubuntu \
$(lsb_release -cs) \
stable"
sudo apt-get update
sudo apt-get install -y docker-ce=18.06.1~ce~3-0~ubuntu
sudo apt-mark hold docker-ce

Verify that Docker is up and running with:
```
sudo systemctl status docker
```

2. Install Kubeadm, Kubelet, and Kubectl on all three nodes.keyboard_arrow_up

Install the Kubernetes components by running this on all three nodes:

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
cat << EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
sudo apt-get update
sudo apt-get install -y kubelet=1.12.7-00 kubeadm=1.12.7-00 kubectl=1.12.7-00
sudo apt-mark hold kubelet kubeadm kubectl

3. Bootstrap the cluster on the Kube master node.keyboard_arrow_up

On the Kube master node, do this:
```
sudo kubeadm init --pod-network-cidr=10.244.0.0/16
```
That command may take a few minutes to complete.
When it is done, set up the local kubeconfig:
```
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
```
Take note that the kubeadm init command printed a long kubeadm join command to the screen.

You will need that kubeadm join command in the next step!
Run the following commmand on the Kube master node to verify it is up and running:
```
kubectl version
```
This command should return both a Client Version and a Server Version.
Join the two Kube worker nodes to the cluster.keyboard_arrow_up
Copy the kubeadm join command that was printed by the kubeadm init command earlier, with the token and hash. Run this command on both worker nodes, but make sure you add sudo in front of it:
sudo kubeadm join $some_ip:6443 --token $some_token --discovery-token-ca-cert-hash $some_hash

Now, on the Kube master node, make sure your nodes joined the cluster successfully:
kubectl get nodes

Verify that all three of your nodes are listed. It will look something like this:

NAME STATUS ROLES AGE VERSION ip-10-0-1-101 NotReady master 30s v1.12.2 ip-10-0-1-102 NotReady 8s v1.12.2 ip-10-0-1-103 NotReady 5s v1.12.2

Note that the nodes are expected to be in the NotReady state for now.
Set up cluster networking with flannel.keyboard_arrow_up
1. Turn on iptables bridge calls on all three nodes:
  echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf sudo sysctl -p
2. Next, run this only on the Kube master node:
  kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml
  
  Now flannel is installed! Make sure it is working by checking the node status again:
  
  kubectl get nodes
  
  After a short time, all three nodes should be in the Ready state. If they are not all Ready the first time you run kubectl get nodes, wait a few moments and try again. It should look something like this:
  
  NAME STATUS ROLES AGE VERSION ip-10-0-1-101 Ready master 85s v1.12.2 ip-10-0-1-102 Ready 63s v1.12.2 ip-10-0-1-103 Ready 60s v1.12.2

How to commit docker images

On June 2, 2019 By Aryan NavaIn DockerLeave a comment

[cloud_user@aryan1c ~]$ docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

To commit docker image, you need to copy the identification number
65d264fc1d7e centos:6 “/bin/bash” 39 minutes ago Exited (0) About a minute ago quirky_nightingale
5fdeaceec288 spacebones/doge “nginx -g ‘daemon …” 2 hours ago Up 2 hours 0.0.0.0:80->80/tcp treatseekers
[cloud_user@aryan1c ~]$ docker commit 65d264fc1d7e spacebones:thewebsite
sha256:d764a58ff47b2db18aec6aa2928b404998130cdba8edcaa6af78ea5f744b651f
[cloud_user@aryan1c ~]$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
spacebones thewebsite d764a58ff47b 4 seconds ago 511 MB

How to install Apache in Linux container

On June 2, 2019 By Aryan NavaIn DockerLeave a comment

[root@65d264fc1d7e /]# yum -y install httpd
Loaded plugins: fastestmirror, ovl
Setting up Install Process
Loading mirror speeds from cached hostfile
* base: mirror.cisp.com
* extras: mirrors.mit.edu
* updates: mirror.trouble-free.net
Resolving Dependencies
–> Running transaction check
—> Package httpd.x86_64 0:2.2.15-69.el6.centos will be installed
–> Processing Dependency: httpd-tools = 2.2.15-69.el6.centos for package: httpd-2.2.15-69.el6.centos.x86_64
–> Processing Dependency: apr-util-ldap for package: httpd-2.2.15-69.el6.centos.x86_64

docker pull

On June 2, 2019 By Aryan NavaIn DockerLeave a comment

How to download docker images and access the images
In this case, I am pulling Centos6 Image from Docker and accessing it using docker run -it centos:6 /bin/bash and updating my image

[cloud_user@aryan1c ~]$ docker pull centos:6
Trying to pull repository docker.io/library/centos …
6: Pulling from docker.io/library/centos
ff50d722b382: Pull complete
Digest: sha256:dec8f471302de43f4cfcf82f56d99a5227b5ea1aa6d02fa56344986e1f4610e7
Status: Downloaded newer image for docker.io/centos:6
[cloud_user@aryan1c ~]$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
docker.io/centos 6 d0957ffdf8a2 2 months ago 194 MB

[cloud_user@aryan1c ~]$ docker run -it centos:6 /bin/bash
[root@65d264fc1d7e /]# ls
bin dev etc home lib lib64 lost+found media mnt opt proc root run sbin selinux srv sys tmp usr var
[root@65d264fc1d7e /]# yum update

*Note: Complete the following section on the MASTER ONLY!

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