Learning Rancher from Zero

Introduction

Rancher consists of rancher-server, rancher-agent, and one or more kubernetes clusters. Among these, rancher-agent runs on the managed kubernetes and communicates with the rancher-server, sending cluster information.

The rancher-server provides a WebUI and API for managing kubernetes. The rancher-server is accessible only via HTTPS.

Installation

Single Node

There are two ways to build a single-node setup:

• Run rancher-server directly with docker
• Use rke to enable all roles on a single node

The rke method will be described later, so here we show the docker method.

On the node where you want to run rancher-server, enter the following command:

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docker run -d --restart=unless-stopped \
  -p 80:80 -p 443:443 \
  rancher/rancher:latest

This will start a single-node rancher-server. You can access it at http://<IP Address>.

Multi Node

Use rke to build an HA environment for rancher-server.

rke (rancher k8s engine) is a command-line tool for building kubernetes clusters. Once the environment is ready, you can build a cluster with a single command.

Prepare Machines

This time, we use multipass to prepare the machines. The following commands create six virtual machines:

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multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kmaster1
multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kmaster2
multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kmaster3
multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kworker1
multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kworker2
multipass launch -c 2 -m 4096M -d 20G --cloud-init=./cloud-init.yaml -n kworker3

The cloud-init.yaml file referenced in the command performs post-setup tasks after the machine boots. In this case, the following tasks are performed:

• Install docker
• Register the host machine’s ssh key
• Add the Ubuntu user to the docker group
• Load required kernel modules
• Disable swap

The details are as follows:

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#cloud-config

packages:
    - docker.io

ssh_authorized_keys:
    - <rsa public key>

runcmd:
    - usermod -aG docker ubuntu
    - modprobe br_netfilter
    - modprobe ip6_udp_tunnel
    - modprobe ip_set
    - modprobe ip_set_hash_ip
    - modprobe ip_set_hash_net
    - modprobe iptable_filter
    - modprobe iptable_nat
    - modprobe iptable_mangle
    - modprobe iptable_raw
    - modprobe nf_conntrack_netlink
    - modprobe nf_conntrack
    - modprobe nf_conntrack_ipv4
    - modprobe nf_defrag_ipv4
    - modprobe nf_nat
    - modprobe nf_nat_ipv4
    - modprobe nf_nat_masquerade_ipv4
    - modprobe nfnetlink
    - modprobe udp_tunnel
    - modprobe veth
    - modprobe vxlan
    - modprobe x_tables
    - modprobe xt_addrtype
    - modprobe xt_conntrack
    - modprobe xt_comment
    - modprobe xt_mark
    - modprobe xt_multiport
    - modprobe xt_nat
    - modprobe xt_recent
    - modprobe xt_set
    - modprobe xt_statistic
    - modprobe xt_tcpudp
    - swapoff -a

In the end, you will have six machines as follows:

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$ multipass list
Name                    State             IPv4             Image
kmaster1                Running           10.131.158.97    Not Available
kmaster2                Running           10.131.158.194   Not Available
kmaster3                Running           10.131.158.121   Not Available
kworker1                Running           10.131.158.133   Not Available
kworker2                Running           10.131.158.247   Not Available
kworker3                Running           10.131.158.166   Not Available

Create Kubernetes Environment with rke

As described in rke, download the binary and add execute permission.

Set the information and roles for the above six nodes. Many other settings are possible, but they are omitted here.

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nodes:
  - address: 10.131.158.97
    user: ubuntu
    role: [controlplane, worker, etcd]
  - address: 10.131.158.194
    user: ubuntu
    role: [controlplane, worker, etcd]
  - address: 10.131.158.121
    user: ubuntu
    role: [controlplane, worker, etcd]
  - address: 10.131.158.133
    user: ubuntu
    role: [worker]
  - address: 10.131.158.247
    user: ubuntu
    role: [worker]
  - address: 10.131.158.166
    user: ubuntu
    role: [worker]

system-images:
    kubernetes: rancher/hyperkube:v1.18.2

services:
  etcd:
    snapshot: true
    creation: 6h
    retention: 24

ingress:
  provider: nginx
  options:
    use-forwarded-headers: 'true'

Run the rke command with this yaml file as a parameter to create the Kubernetes environment.

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rke_linux-amd64 up --config ./rancher_cluster.yaml

After the cluster is successfully created, two new files will be generated in addition to the original yaml file.

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$ ll
total 132K
-rw-r----- 1 wshi wshi 5.3K Jun  8 17:04 kube_config_rancher_cluster.yaml
-rw-r----- 1 wshi wshi 119K Jun  8 17:07 rancher_cluster.rkestate
-rw-rw-r-- 1 wshi wshi  748 Jun  8 16:53 rancher_cluster.yaml

Among these, kube_config_rancher_cluster.yaml is the configuration file for accessing the cluster. Copy it to ~/kube/config so that it can be loaded by kubectl. Now you can access the cluster.

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$ kubectl get node
NAME             STATUS   ROLES                      AGE   VERSION
10.131.158.121   Ready    controlplane,etcd,worker   21h   v1.17.4
10.131.158.133   Ready    worker                     21h   v1.17.4
10.131.158.166   Ready    worker                     21h   v1.17.4
10.131.158.194   Ready    controlplane,etcd,worker   21h   v1.17.4
10.131.158.247   Ready    worker                     21h   v1.17.4
10.131.158.97    Ready    controlplane,etcd,worker   21h   v1.17.4

Install Rancher on Kubernetes

Follow the Rancher documentation for installation. Here, only the installation steps are extracted; for detailed settings, refer to the documentation.

1. Install helm

   Refer to the helm homepage to install helm.

   1	sudo snap install helm --classic

2. Add the rancher repository to helm

   This time, select stable.

   1	helm repo add rancher-stable https://releases.rancher.com/server-charts/stable

3. Add a namespace for installing rancher

   The namespace name must be cattle-system.

   1	kubectl create namespace cattle-system

4. Install cert-manager

   There are other ways to create certificates, but here we let rancher generate them.

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   # Install the CustomResourceDefinition resources separately kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/download/v0.15.0/cert-manager.crds.yaml # Create the namespace for cert-manager kubectl create namespace cert-manager # Add the Jetstack Helm repository helm repo add jetstack https://charts.jetstack.io # Update your local Helm chart repository cache helm repo update # Install the cert-manager Helm chart helm install \ cert-manager jetstack/cert-manager \ --namespace cert-manager \ --version v0.15.0

   Check the status of cert-manager:

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   $ kubectl get pods --namespace cert-manager NAME READY STATUS RESTARTS AGE cert-manager-766d5c494b-9cmcq 1/1 Running 0 15s cert-manager-cainjector-6649bbb695-cfmxq 1/1 Running 0 15s cert-manager-webhook-68d464c8b-5bmjt 1/1 Running 0 15s

5. Install rancher-server

   Install rancher-server using Rancher-generated certificates.

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   helm install rancher rancher-stable/rancher \ --namespace cattle-system \ --set hostname=rancher.my.org

   Check the status of rancher-server:

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   $ kubectl get pod -n cattle-system -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES rancher-756b996499-fjnt9 1/1 Running 0 35m 10.42.0.4 10.131.158.247 <none> <none> rancher-756b996499-rkn8h 1/1 Running 0 35m 10.42.2.4 10.131.158.121 <none> <none> rancher-756b996499-wmczg 1/1 Running 0 35m 10.42.5.4 10.131.158.97 <none> <none>

   Pods on each node are in Running state, indicating successful installation.