Just 5 minutes! Quick tutorial of deploying lightweight Kubernetes cluster with k3s

Keywords: Kubernetes sudo Linux github

K3s, which is only 40MB in size, provides a good choice for enterprises that want to save cost for development and testing. In a very simple way, this article will teach you to deploy a lightweight Kubernetes cluster in 5 minutes using k3s.

This article comes from: Rancher Labs

Kubernetes has changed how to deploy and manage containerized workloads on a large scale. Now developers are faced with the challenges of the complexity of the setup process and huge resource requirements. If you are plagued by insufficient memory and want to deploy a lightweight kubernetes cluster to reduce memory consumption, you must consider the lightweight kubernetes distribution, k3s, released by Rancher Labs. It packs all the files needed to install kubernetes into a 40MB binary file, which only needs 512MB RAM to run. It is very suitable for environments with limited resources, such as edge computing scenarios, IoT, etc.

In the actual scenario, in order to obtain the power of development and testing and save the cost, users hope to deploy Kubernetes with the least resource utilization and lower hardware specifications. k3s meets this demand. It can run clusters on any device with more than 512MB RAM, such as IoT devices or ARM driven devices.

Since k3s only needs a small amount of resources to run, this means that some features of Kubernetes have been removed:

  • Old, non default, alpha features

  • Most in tree plug-ins (cloud providers and storage plug-ins) are replaced with add ons

  • Using sqlite instead of etcd as the default storage mechanism

Deploy lightweight K8s cluster with k3s in 5 minutes

In this article, I'll use three servers running on Debian 10, each with 1GB of RAM and 1vcpu. One server is the master and the other two are the worker nodes.


$ openstack server list
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+
| ID                                   | Name              | Status  | Networks                          | Image     | Flavor    |
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+
| 4df6a6dc-26e8-4ae0-8b6e-2f97daec0ef3 | k3s-master        | ACTIVE  | private=10.10.1.159               | Debian-10 | m1.tiny   |
| 5ca13239-b745-4f62-ab11-0a27949c9b35 | k3s-node02        | ACTIVE  | private=10.10.1.142               | Debian-10 | m1.tiny   |
| a54997f2-4d94-4718-86ab-73609b328761 | k3s-node01        | ACTIVE  | private=10.10.1.126               | Debian-10 | m1.tiny   |
+--------------------------------------+-------------------+---------+-----------------------------------+-----------+-----------+

I will add A record for each server in the / etc / hosts file.

sudo tee -a /etc/hosts<<EOF
10.10.1.159 k3s-master
10.10.1.126 k3s-node01
10.10.1.142 k3s-node02
EOF

Install k3s on the Master node

There are many ways to run k3s. The fastest way is to install it through the bash script provided. At the same time, the script provides a convenient way to install it to systemd or openrc.

curl -sfL https://get.k3s.io | sh -

Install output:

[INFO]  Finding latest release
[INFO]  Using v0.8.1 as release
[INFO]  Downloading hash https://github.com/rancher/k3s/releases/download/v0.8.1/sha256sum-amd64.txt
[INFO]  Downloading binary https://github.com/rancher/k3s/releases/download/v0.8.1/k3s
[INFO]  Verifying binary download
[INFO]  Installing k3s to /usr/local/bin/k3s
[INFO]  Creating /usr/local/bin/kubectl symlink to k3s
[INFO]  Creating /usr/local/bin/crictl symlink to k3s
[INFO]  Creating /usr/local/bin/ctr symlink to k3s
[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
[INFO]  Creating uninstall script /usr/local/bin/k3s-uninstall.sh
[INFO]  env: Creating environment file /etc/systemd/system/k3s.service.env
[INFO]  systemd: Creating service file /etc/systemd/system/k3s.service
[INFO]  systemd: Enabling k3s unit
Created symlink /etc/systemd/system/multi-user.target.wants/k3s.service → /etc/systemd/system/k3s.service.
[INFO]  systemd: Starting k3s

After the installation is complete, the service starts automatically.

$ systemctl status k3s
● k3s.service - Lightweight Kubernetes
   Loaded: loaded (/etc/systemd/system/k3s.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2019-09-17 19:20:00 UTC; 2min 24s ago
     Docs: https://k3s.io
  Process: 833 ExecStartPre=/sbin/modprobe br_netfilter (code=exited, status=0/SUCCESS)
  Process: 836 ExecStartPre=/sbin/modprobe overlay (code=exited, status=0/SUCCESS)
 Main PID: 837 (k3s-server)
    Tasks: 98
   Memory: 571.1M
   CGroup: /system.slice/k3s.service
           ├─ 837 /usr/local/bin/k3s server KillMode=process
           ├─ 851 containerd -c /var/lib/rancher/k3s/agent/etc/containerd/config.toml -a /run/k3s/containerd/containerd.sock --state /run/k3s/conta
           ├─1110 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/f6eeb59978
           ├─1127 /pause
           ├─1207 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/0baf0ca181
           ├─1225 /coredns -conf /etc/coredns/Corefile
           ├─1576 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/dcce4b7e17
           ├─1594 /pause
           ├─1599 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/50816ffba8
           ├─1617 /pause
           ├─1824 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/d0ff393609
           ├─1842 /bin/sh /usr/bin/entry
           ├─1882 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/046779175f
           ├─1899 /bin/sh /usr/bin/entry
           ├─1904 containerd-shim -namespace k8s.io -workdir /var/lib/rancher/k3s/agent/containerd/io.containerd.runtime.v1.linux/k8s.io/93f0fe2361
           └─1921 /traefik --configfile=/config/traefik.toml

Sep 17 19:20:34 deb10 k3s[837]: E0917 19:20:34.714229     837 daemon_controller.go:302] kube-system/svclb-traefik failed with : error storing statu
Sep 17 19:20:34 deb10 k3s[837]: E0917 19:20:34.719452     837 daemon_controller.go:302] kube-system/svclb-traefik failed with : error storing statu
Sep 17 19:20:34 deb10 k3s[837]: I0917 19:20:34.726816     837 reconciler.go:207] operationExecutor.VerifyControllerAttachedVolume started for volum
Sep 17 19:20:34 deb10 k3s[837]: I0917 19:20:34.726836     837 reconciler.go:207] operationExecutor.VerifyControllerAttachedVolume started for volum
Sep 17 19:20:34 deb10 k3s[837]: I0917 19:20:34.726857     837 reconciler.go:207] operationExecutor.VerifyControllerAttachedVolume started for volum
Sep 17 19:20:34 deb10 k3s[837]: I0917 19:20:34.726869     837 reconciler.go:207] operationExecutor.VerifyControllerAttachedVolume started for volum
Sep 17 19:20:35 deb10 k3s[837]: I0917 19:20:35.529102     837 reconciler.go:181] operationExecutor.UnmountVolume started for volume "helm-traefik-t
Sep 17 19:20:35 deb10 k3s[837]: I0917 19:20:35.542858     837 operation_generator.go:799] UnmountVolume.TearDown succeeded for volume "kubernetes.i
Sep 17 19:20:35 deb10 k3s[837]: I0917 19:20:35.629277     837 reconciler.go:285] Volume detached for volume "helm-traefik-token-kjwrl" (UniqueName:
Sep 17 19:20:36 deb10 k3s[837]: W0917 19:20:36.355273     837 pod_container_deletor.go:75] Container "2f0c4a787b13c029d65aa865c1b473f5a7497cb6f9b92

Write the kubeconfig file to / etc/rancher/k3s/k3s.yaml:

$ cat /etc/rancher/k3s/k3s.yaml
cat: /etc/rancher/k3s/k3s.yaml: Permission denied
debian@deb10:~$ sudo cat /etc/rancher/k3s/k3s.yaml
apiVersion: v1
clusters:
- cluster:
    certificate-authority-data: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSUJWakNCL3FBREFnRUNBZ0VBTUFvR0NDcUdTTTQ5QkFNQ01DTXhJVEFmQmdOVkJBTU1HR3N6Y3kxelpYSjIKWlhJdFkyRkFNVFUyT0RjME56azVOakFlRncweE9UQTVNVGN4T1RFNU5UWmFGdzB5T1RBNU1UUXhPVEU1TlRaYQpNQ014SVRBZkJnTlZCQU1NR0dzemN5MXpaWEoyWlhJdFkyRkFNVFUyT0RjME56azVOakJaTUJNR0J5cUdTTTQ5CkFnRUdDQ3FHU000OUF3RUhBMElBQkM5aTMyUTdkVnhJaTFCVFNEOTRqYzJaZy9ESHFGc051b0Q4eWhSbjZsUlIKQWp5Q0p3UEZYQ3Y4QUdSMmFaK1lSempTYUJvM2M1LzMwQnZwKzY3OFNYeWpJekFoTUE0R0ExVWREd0VCL3dRRQpBd0lDcERBUEJnTlZIUk1CQWY4RUJUQURBUUgvTUFvR0NDcUdTTTQ5QkFNQ0EwY0FNRVFDSUJwTXdOejAyZzUwCkExdEloU0Y1MFJqSVprVVVuNk8rODdLV25obWRUYkh5QWlBQnJqcDFxWU1HcWE0RmJ2Ym9rTm1kM3VOelVvQm8KeGxqTGlnWnZCN3ZEVGc9PQotLS0tLUVORCBDRVJUSUZJQ0FURS0tLS0tCg==
    server: https://localhost:6443
  name: default
contexts:
- context:
    cluster: default
    user: default
  name: default
current-context: default
kind: Config
preferences: {}
users:
- name: default
  user:
    password: 2d99cae31c075743be704bb717ceaae8
    username: admin

Other installed ones are:

  • kubectl

  • crictl

  • k3s-killall.sh

  • k3s-uninstall.sh

Install k3s on Worker node

To install k3s on the Woker node, we should pass the k3s'url along with the k3s'token or k3s'cluster'secret environment variable.

K3S_TOKEN is created in / var / lib / lancher / k3s / server / node token on the first node.

$ sudo cat /var/lib/rancher/k3s/server/node-token
K1042e2f8e353b9409472c1e0cca8457abe184dc7be3f0805109e92c50c193ceb42::node:c83acbf89a7de7026d6f6928dc270028

So in order to install Kubernetes on the worker node, I will run:

k3s_url="https://k3s-master:6443"
k3s_token="K1042e2f8e353b9409472c1e0cca8457abe184dc7be3f0805109e92c50c193ceb42::node:c83acbf89a7de7026d6f6928dc270028"
curl -sfL https://get.k3s.io | K3S_URL=${k3s_url} K3S_TOKEN=${k3s_token} sh -

Install output:

[INFO]  Finding latest release
[INFO]  Using v0.8.1 as release
[INFO]  Downloading hash https://github.com/rancher/k3s/releases/download/v0.8.1/sha256sum-amd64.txt
[INFO]  Downloading binary https://github.com/rancher/k3s/releases/download/v0.8.1/k3s
[INFO]  Verifying binary download
[INFO]  Installing k3s to /usr/local/bin/k3s
[INFO]  Creating /usr/local/bin/kubectl symlink to k3s
[INFO]  Creating /usr/local/bin/crictl symlink to k3s
[INFO]  Creating /usr/local/bin/ctr symlink to k3s
[INFO]  Creating killall script /usr/local/bin/k3s-killall.sh
[INFO]  Creating uninstall script /usr/local/bin/k3s-agent-uninstall.sh
[INFO]  env: Creating environment file /etc/systemd/system/k3s-agent.service.env
[INFO]  systemd: Creating service file /etc/systemd/system/k3s-agent.service
[INFO]  systemd: Enabling k3s-agent unit
Created symlink /etc/systemd/system/multi-user.target.wants/k3s-agent.service → /etc/systemd/system/k3s-agent.service.
[INFO]  systemd: Starting k3s-agent

Log in to one of the master nodes and check the cluster status:

$ sudo kubectl config get-clusters 
NAME
default

$ sudo kubectl cluster-info 
Kubernetes master is running at https://localhost:6443
CoreDNS is running at https://localhost:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

$ sudo kubectl get  nodes
NAME         STATUS   ROLES    AGE     VERSION
k3s-master   Ready    master   14m     v1.14.6-k3s.1
k3s-node01   Ready    worker   3m11s   v1.14.6-k3s.1
k3s-node02   Ready    worker   3m58s   v1.14.6-k3s.1

$ sudo kubectl get namespaces
NAME              STATUS   AGE
default           Active   16m
kube-node-lease   Active   16m
kube-public       Active   16m
kube-system       Active   16m

$ sudo  kubectl get endpoints -n kube-system
NAME       ENDPOINTS                                  AGE
kube-dns   10.42.0.2:53,10.42.0.2:53,10.42.0.2:9153   14m
traefik    10.42.0.5:80,10.42.0.5:443                 14m

$ sudo kubectl get pods -n kube-system
NAME                         READY   STATUS      RESTARTS   AGE
coredns-b7464766c-q9frk      1/1     Running     0          15m
helm-install-traefik-8dhpk   0/1     Completed   0          15m
svclb-traefik-9c2j8          2/2     Running     0          4m49s
svclb-traefik-bf9zd          2/2     Running     0          4m2s
svclb-traefik-v2fpx          2/2     Running     0          14m
traefik-5c79b789c5-k589d     1/1     Running     0          14m

Use the crictl command to view running containers

# Master
$ sudo crictl ps
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT             POD ID
acfafb50852d3       18471c10e6e4b       16 minutes ago      Running             traefik             0                   bf8534452389f
fee5ac7e88f2e       4a065d8dfa588       16 minutes ago      Running             lb-port-443         0                   e7068ff7ab2f2
bbab5b07e5efb       4a065d8dfa588       16 minutes ago      Running             lb-port-80          0                   e7068ff7ab2f2
65c5d1333ea04       2ee68ed074c6e       16 minutes ago      Running             coredns             0                   435c51f4716fc

# Workers
$ sudo crictl ps
CONTAINER ID        IMAGE               CREATED             STATE               NAME                ATTEMPT             POD ID
7ad5c83d6466f       4a065d8dfa588       6 minutes ago       Running             lb-port-443         0                   bf8d9fe57c3f3
c1380eabc0b33       4a065d8dfa588       6 minutes ago       Running             lb-port-80          0                   bf8d9fe57c3f3

It's done! If you need more advanced configuration, please refer to the k3s documentation:

https://rancher.com/docs/k3s/latest/en/

Posted by djp120 on Thu, 31 Oct 2019 23:41:20 -0700

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