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K3s – A Practical Introduction

K3s – A Practical Introduction

More and more businesses are running distributed payloads closer to their data, reducing costs and increasing availability. This talk provides a quick introduction to K3s and how to use to create edge computing solutions. This technical webinar, targeted to IT managers and software developers, includes a live demo.

Video: https://www.youtube.com/watch?v=XKaMYU4lgI4

Adrian Kosmaczewski

September 30, 2021
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  1. VSHN – The DevOps Company
    Adrian Kosmaczewski, Developer Relations
    K3s – A Practical
    Introduction
    Thursday, September 30th, 2021
    Welcome and thank you so much for joining this
    webinar! My name is Adrian Kosmaczewski, I’m
    Developer Relations at VSHN, the DevOps company,
    and I greet you from the beautiful city of Zürich,
    Switzerland. Today it’s Thursday, September 30th,
    2021, and today we’re going to be talking about the
    K3s Kubernetes distribution.
    There’s a Q&A box for your questions, so please feel
    free to ask questions as the talk progresses, and I will
    answer them at the end of the presentation.
    Speaker notes
    1

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  2. VSHN – The DevOps Company
    Pronounced ˈvɪʒn – like "vision"
    The DevOps Company
    Founded 2014, 46 VSHNeers located in Zürich (we’re hiring!)
    Switzerland’s leading DevOps, Docker & Kubernetes partner
    24/7 support
    ISO 27001 certi ed
    ISAE 3402 Report Type 1 veri ed
    First Swiss Kubernetes Certi ed Service Provider
    Just a few words about VSHN; that’s how you
    pronounce the name, and we’re "The DevOps
    Company". We’ve been in Zurich since 2014, we’re 46
    VSHNeers and we’re Switzerland’s leading DevOps,
    Docker & Kubernetes partner, offering 24/7 support to
    our customers. We’ve got a few certifications, and most
    importantly, we were the First Swiss Kubernetes
    Certified Service Provider back in 2016.
    Speaker notes
    2

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  3. VSHN – The DevOps Company
    We also run our own "Platform as a Service" offering
    called "APPUiO". We’ve created our own suite of tools
    to manage lots of Kubernetes services from a central
    location, called "Project Syn". Last but not least, we
    have developed our own Kubernetes operator for
    backups, called K8up, which just like Project Syn is
    100% open source on GitHub.
    Speaker notes
    3

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  4. VSHN – The DevOps Company
    We’re partners with many companies very active in the
    Cloud Native space, you might recognize some of the
    logos on this slide. Of course tonight we’re going to talk
    about SUSE and one of the their most fantastic
    products.
    Speaker notes
    4

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  5. VSHN – The DevOps Company
    But of course the star of the evening is K3s, so let’s
    get started and learn what is K3s and how we can use
    it.
    Speaker notes
    5

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  6. VSHN – The DevOps Company
    1. What is K3s?
    2. What is it used for?
    3. How does it work?
    4. Demo time!
    5. Where to nd more information?
    Agenda
    The agenda for today is quite simple, and will consist of
    five major sections: first we’re going to learn what is
    K3s, and what it is used for; then we are going to learn
    how it works, and of course, we’re going to have a small
    demo of K3s in action, live. Finally I will give you some
    pointers to additional information about K3s, for you to
    continue your discovery path.
    Speaker notes
    6

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  7. VSHN – The DevOps Company
    1. What is K3s?
    So, on to the first point: what is K3s?
    Speaker notes
    7

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  8. VSHN – The DevOps Company
    Kubernetes distribution
    Lightweight
    Simple to install, use, and maintain
    Optimized for ARM
    Fully open source
    in February 2019
    in November 2019
    CNCF Sandbox Project since June 2020
    Website:
    Fully Conformant
    Introduced by Rancher
    Version 1.0
    k3s.io
    K3s is a fully conformant Kubernetes distribution. The
    link on the slide points directly to the location of the
    automated conformance tests that prove that each
    release of K3s passes all required criteria.
    But it is not just any Kubernetes distribution; it is a very
    lightweight one, distributed as a single binary of less
    than 50 MB. Very simple to install, use, and maintain, it
    is optimized for ARM CPUs, which makes it a great
    distribution to use with Raspberry Pis and other small
    boards. It is fully open source, introduced in 2019, and
    donated to the CNCF in June 2020.
    Speaker notes
    8

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  9. VSHN – The DevOps Company
    len("Kubernetes") = 10 ⇒ "K8s"
    len("K___s") ⇒ "K3s"
    Nobody knows what the _ stands for!
    No of cial pronunciation
    About the Name
    = 5 =
    10
    2
    The same way I explained to you how to pronounce the
    word "VSHN" at the beginning of this session, let me
    explain to you the origin of the name K3s. There is an
    algorithm behind, as you’ll see.
    You all know that Kubernetes is commonly referred to
    as K8s; well, it turns out the Kubernetes word is 10
    letters long; and since K3s requires half the memory of
    Kubernetes, they looked for a word with 5 letters, which
    would be cut as "K3s".
    Of course, nobody knows what would go in between the
    "K" and the "S", and there’s no official pronounciation.
    So, "Kay three ess" is the way to say it.
    Speaker notes
    9

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  10. VSHN – The DevOps Company
    2. What is K3s Used for?
    We all associate Kubernetes with big clusters. So, what
    can we use K3s for?
    Speaker notes
    10

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  11. VSHN – The DevOps Company
    Edge
    IoT
    Development
    CI/CD
    Embedded / ARM
    Teaching / Learning
    Use Cases
    K3s has a lot of interesting use cases. These days lots
    of companies are moving into the "Edge computing"
    area, distributing workloads into laptops and small
    devices. K3s is an ideal distribution for that, just as for
    the "Internet of Things". Developers can install it in
    their laptops to simulate deployments in
    It can be used as a CI/CD platform, to embed in your
    pipelines, applying deployments and performing
    integration tests. It can work in embedded devices with
    ARM CPUs, and of course, it’s a great way to learn (and
    teach) Kubernetes to engineers.
    Speaker notes
    11

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  12. VSHN – The DevOps Company
    Source:
    "Situations where a PhD in K8s clusterology is
    infeasible"
    rancher.com/docs/k3s/latest/en
    But by far the best use case is the one quoted in this
    slide, which is actually mentioned in the K3s
    documentation: "K3s is a great Kubernetes option
    when a PhD in clusterology is infeasible." Just perfect.
    Speaker notes
    12

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  13. VSHN – The DevOps Company
    APPUiOli at
    K3s at VSHN
    K8up Getting Started guide
    Writing Project Syn components tutorial
    KubeCon 2019 Barcelona
    At VSHN we’ve been great fans of K3s since it first
    came out. We started using it in demos and
    presentations as soon as it appeared. For example, the
    getting started guide for K8up, our Kubernetes backup
    operator, uses K3s; just like the tutorial to learn how to
    write Commodore components to use with Project Syn.
    Last but not least, we’ve demoed APPUiOli during our
    visit to KubeCon 2019 in Barcelona.
    Speaker notes
    13

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  14. VSHN – The DevOps Company
    And if you wonder what is APPUiOli, well, here it is: a
    small Kubernetes cluster made of ARM boards, running
    K3s in its core.
    Source:
    Speaker notes
    tobru.ch/kubernetes-on-orangepi-arm64
    14

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  15. VSHN – The DevOps Company
    Lightweight
    50% memory requirements
    Single binary
    < 50 MB binary with all components
    SQLite3 backend
    Packaged addons
    Secure by default
    Features
    K3s has many features, but by far the most important
    is that it is very lightweight; not only it consumes "half
    the memory" required by a standard Kubernetes
    cluster, it is also deployed as a lightweight single binary
    (written in Go) which weighs less than 50 MB.
    Instead of using etcd, it uses SQLite by default; it has
    many packaged addons (which can be enabled and
    disabled as needed at startup) and it has been built
    with security in mind.
    Speaker notes
    15

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  16. VSHN – The DevOps Company
    Flannel
    Helm
    Trae k (default ingress)
    CoreDNS

    Packaged Addons
    Speaking about the addons, here are some of the most
    common: Flannel, Helm, Traefik, CoreDNS, and many
    more.
    By the way, Traefik is the default ingress, but as I said,
    it can be disabled, so that you can install your own
    ingress component.
    Speaker notes
    16

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  17. VSHN – The DevOps Company
    3. How does K3s Work?
    Let us dive a bit deeper in the mechanisms that make
    K3s so good.
    Speaker notes
    17

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  18. VSHN – The DevOps Company
    1. Server
    Packaged control plane
    API + Scheduler + Controller Manager + sqlite3 + tunnel proxy
    2. Agent
    Worker node
    Tunnel proxy + kube proxy + kubelet + Flannel
    3. Outside of K3s processes:
    containerd + pod + pod + pod + …
    Architecture
    Just like any other Kubernetes cluster, we have master
    nodes, and worker nodes. In K3s terminology, we have
    the Server, which is the master node; it contains a full
    packaged control plane, with all of the required
    components in it.
    On the other side, we have one or many Agents, which
    are the worker nodes; they also contain all they need to
    run pods and workloads.
    Finally, all pods run outside of the main K3s processes,
    using containerd.
    Speaker notes
    18

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  19. VSHN – The DevOps Company
    At least 2 GB of RAM
    Documentation states 512 MB but
    1 CPU (2 recommended for K3s server)
    SSD (recommended)
    Requirements
    pull request
    To run the latest versions of K3s we need at least 2 GB
    of RAM available for the Server, and around 1 GB
    available per Agent. Pay attention, since the
    documentation still states 512 MB of RAM minimum,
    but there’s an open pull request on GitHub to correct
    that mistake.
    Also, each Server and Agent require a CPU, but in the
    case of the Server, it’s better to assign 2 CPUs.
    For storage, of course, using an SSD drive is way
    faster.
    Speaker notes
    19

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  20. VSHN – The DevOps Company
    Most Linux distributions
    Special instructions for
    Raspian Buster
    Alpine Linux
    RHEL / CentOS
    Windows not supported
    Operating System
    K3s has been designed with Linux in mind; K3s runs in
    the most popular distributions, starting with SUSE Linux
    and openSUSE of course.
    In the documentation there are some special sections
    for Raspian (for use in Raspberry Pi devices), Alpine
    Linux, and RHEL & CentOS.
    Be aware, however, that at this time K3s does not run
    natively in Windows.
    Speaker notes
    20

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  21. VSHN – The DevOps Company
    API server (TCP port 6443)
    Flannel VXLAN (UDP port 8472)
    Metrics server (TCP port 10250)
    Network Ports
    A K3s cluster with default settings will expose, as
    expected, the Kubernetes API on port 6443, plus some
    other ports that expose VXLAN and metrics information.
    Speaker notes
    21

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  22. VSHN – The DevOps Company
    Default SQLite
    For large clusters:
    MySQL
    PostgreSQL
    etcd
    Datastore shim: Kine
    Database
    github.com/k3s-io/kine
    I mentioned earlier that K3s uses SQLite by default; but
    for larger clusters, you can switch it to MySQL,
    PostgreSQL, or even etcd, thanks to the Kine project,
    which provides a layer of abstraction between K3s and
    the underlying data store.
    Speaker notes
    22

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  23. VSHN – The DevOps Company
    1. Server 2. Agent(s)
     Each node must have a
    unique hostname:
    K3S_NODE_NAME to override.
    Installation
    $ curl -sfL https://get.k3s.io | sh -
    $ cat /var/lib/rancher/k3s/server/node-token
    $ cat /etc/rancher/k3s/k3s.yaml
    $ export K3S_URL=https://server:6443
    $ export K3S_TOKEN=...
    $ curl -sfL https://get.k3s.io | sh -
    To install K3s, you need two or more machines
    (physical, virtual, or containers); the first one will
    contain the Server, and it can be bootstrapped very
    easily using the curl command shown on screen.
    Once this is done, K3s is configured to automatically
    restart in case of a reboot, and it exposes two
    important files: the token used to attach new Agents to
    this server, and the Kubeconfig file, which can be used
    by kubectl or similar tools to talk to the Kubernetes
    API.
    For each Agent, we need at least to specify two
    environment variables: K3S_URL contains the URL of the
    Kubernetes API exposed by the server; and K3S_TOKEN
    contains the value of the token stored in the server.
    Speaker notes
    23

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  24. VSHN – The DevOps Company
    Other Ways to Install
    github.com/eezhee/eezhee
    k3sup.dev
    Of course, installing K3s is fun once or twice, but it can
    quickly become boring; so there are more ways to run a
    K3s cluster these days.
    First of all, we need to mention the k3d project, which
    allows, as the name implies, to run "K3s in Docker".
    Another option is to use K3OS, a Linux distribution
    specially created just to run K3s. We’re going to talk
    more about it in a minute.
    And if you need more help, here’s the eezhee and k3sup
    projects, which both allow to easily bootstrap K3s
    clusters. eezhee is meant to be create clusters in
    DigitalOcean, Linode and Vultr, while k3sup works for
    any node where you have SSH access.
    Speaker notes
    24

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  25. VSHN – The DevOps Company
    1 Creates a K3s cluster in Docker with 1 server and 3 agents
    2 Retrieves kubeconfig
    Website:
    #!/usr/bin/env bash
    HOSTNAME=rancher-demo.eu.ngrok.io
    k3d cluster create k3s-rancher --servers 1 --agents 3
    k3d kubeconfig get k3s-rancher > k3s.kubeconfig
    # Install cert-manager
    helm --kubeconfig k3s.kubeconfig install cert-manager jetstack/cert-manager --namespace cert-manager \
    --create-namespace --version v1.3.1 --set installCRDs=true
    kubectl --kubeconfig k3s.kubeconfig -n cert-manager rollout status deploy/cert-manager
    # Install Rancher
    helm --kubeconfig k3s.kubeconfig install rancher rancher-latest/rancher --namespace cattle-system \
    --create-namespace --set hostname=$HOSTNAME
    kubectl --kubeconfig k3s.kubeconfig -n cattle-system rollout status deploy/rancher
    1
    2
    k3d.io
    Let’s talk a bit about k3d, which is at VSHN our
    preferred way to spin up a new K3s cluster easily. The
    command k3d cluster create will basically do that for
    us, in a few seconds, and then we can retrieve the
    kubeconfig using the k3d kubeconfig get command.
    In the example in this slide, we are then using the
    Kubeconfig to install cert-manager and the Rancher
    cluster management tool.
    Speaker notes
    25

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  26. VSHN – The DevOps Company
    Full Linux distribution just for K3s!
    Boots with a K3s cluster ready to use
    Built with linuxkit
    Ubuntu 20.04 kernel
    Alpine userland (BusyBox)
    OpenRC init system
    April 2019
    Website:
    Announced
    k3os.io
    And finally, a word about K3OS; this is a crazy project,
    meant to create a small Linux distribution that boots a
    K3s cluster, ready to use! It is built with linuxkit, and its
    upstream kernel is Ubuntu 20.04. It uses an Alpine
    userland based on BusyBox, and uses OpenRC as init
    system. It was announced in April 2019.
    Speaker notes
    26

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  27. VSHN – The DevOps Company
    4. See K3s in Action!
    Finally! Lots of words, zero action; let’s see how K3s
    work in real life.
    In this demo we’re going to see K3s running in
    VirtualBox with Vagrant, and then we’re going to use
    K3d to spin up a new cluster quickly.
    Speaker notes
    27

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  28. VSHN – The DevOps Company
    5. More Information?
    Now that we’ve seen what K3s is and how it works, let’s
    see what the community is doing with it.
    Speaker notes
    28

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  29. VSHN – The DevOps Company
    GitHub Action for K3s
    Visual Studio Code extension
    "i built a Raspberry Pi SUPER COMPUTER!! // ft. Kubernetes
    (k3s cluster w/ Rancher)" (July 2021)
    Ideas
    github.com/debianmaster/actions-k3s
    github.com/inercia/vscode-k3d
    www.youtube.com/watch?v=X9fSMGkjtug
    People are becoming crazy with K3s, and there’s a lot
    of interesting things being built around it. Suffice to
    mention the GitHub Actions for K3s, which allow
    developers to create a small cluster in their GitHub
    Action pipelines; and the Visual Studio Code extension
    for K3d, which gives you quick access to your local
    clusters.
    Speaker notes
    29

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  30. VSHN – The DevOps Company
    K3s with Vagrant
    Introduction by Rancher (May 2021)
    A Cloud Guru course
    5 Reasons to Use K3s (Sept 2020)
    Links
    gitlab.com/akosma/k3s-in-vagrant
    rancher.com/blog/2021/introduction-to-k3s
    acloudguru.com/course/introduction-to-k3s
    acloudguru.com/blog/engineering/5-reasons-to-use-k3s
    And here are some interesting links for you to discover
    more about K3s.
    Speaker notes
    30

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  31. VSHN – The DevOps Company
    Adrian Kosmaczewski, Developer Relations –
    VSHN AG – Neugasse 10 – CH-8005 Zürich – +41 44 545 53 00 – –
    Thanks!
    [email protected]
    vshn.ch [email protected]
    Thanks a lot for your attention! I hope that this short
    introduction to K3s has been interesting to you and that
    you will launch many K3s clusters in the future.
    Speaker notes
    31

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