---
title: Building a Docker Swarm With Pi's
date: 2021-12-12T17:23:32Z
author: "ahmza"
draft: false
weight: 

tags: ["Homelab","Docker","Docker Swarm","Raspberry Pi","Pi4"]
description: "Pis are very capable computers, when banded together they're almost unstoppable"
canonicalURL: "https://blog.ahmza.com/Page%28/posts/building-a-docker-swarm-with-pis.md%29"

cover:
    image: "/img/pi-docker-swarm/pi-swarm.gif" # image path/url
    alt: "Pi Docker Swarm" # alt text
    caption: "<text>" # display caption under cover
    relative: false # when using page bundles set this to true
showtoc: true
searchHidden: false
---

## **Intro**
The _Raspberry Pi_ from it's first iteration has been a great hit.
Adopted by many as the computer of choice for projects, and for
very good reason. The Pi is a fully fledged computer that fits in
your pocket and the most recent edition has blown fans away with
the flagship model boasting an ARM64 CPU and 8GB of RAM.

Now one _Raspberry Pi 4 8GB_ is more than powerful enough for most
workloads and in some cases totally unnecessary, **so you may even
get away with a single 4GB model**. However taking into consideration
their relatively low price and power consumption why not go all out
and build a cluster.

> **You can never have too many _Raspberry Pis_, just
not enough Ideas**

My excuse to build a Pi cluster is, I would like to migrate the
services currently running on a **bare metal server that sucks
a lot of power to a low power solution.** What better way to do that
than a Pi cluster.

### **My Setup**
* 4 x _Raspberry Pi 4 8GB_
* 4 x 32GB SD cards
* 4 x PoE hats
* 1 x 5 port PoE Switch

![Cluster](/img/pi-docker-swarm/cluster.webp)

### **Point of this post**
Hopefully after following this post you will have setup _Docker
swarm_ on a cluster of Pis **- stay even if you currently only have
one -** and understand how to bend it to your will 🦾. 

### **Why** ***Docker Swarm*** 🧐
While we can manage each docker node - _Raspberry Pi_ - individually
, **_Docker swarm_ enables us to manage all the devices from a single
main node** making managing the cluster a lot easier.

Think of _Docker swarm_ as a set of 🤖 hands which will run tasks on
each individual node for us. These tasks can consist of:
* Cluster Management
* Deployment and Scaling across the cluster
* Multi-host networking
* load balancing
* etc...

### **Well why not** ***Kubernetes***
Although _Kubernetes_ is awesome, **it adds a bunch of complexity that
is simply not needed in a home lab environment** where we only have
a small cluster. As well as that, from my experience creating
```docker-compose``` files is a lot easier than writing manifests.
**_Docker swarm_ can do everything I want it to and requires less
effort** which is great if you're like me 🥱 😂

### **Required Stuff**
> The links below are reccomendations/stuff I used
* [_Raspberry Pi_ 4B](https://thepihut.com/products/raspberry-pi-4-model-b?variant=31994565689406) (Reccomend 4-8 @ 8GB)
* [_Raspberry Pi_ PoE Hats](https://thepihut.com/products/power-over-ethernet-poe-hat-d-for-raspberry-pi) (If you can find the [PoE+](https://thepihut.com/products/raspberry-pi-poe-plus-hat) version get them)
* [Cluster Case](https://thepihut.com/products/cluster-case-for-raspberry-pi) (Get any case you want)
* [PoE switch](https://www.amazon.co.uk/gp/product/B076982FVC/) (Get one that has enough ports for the nuber of pis you want)
* [RJ45 Ethernet Cable](https://www.amazon.co.uk/gp/product/B00C4U030G) (Reccomend short cables as it will look neater)
* [Micro SD cards](https://www.amazon.co.uk/gp/product/B08J4HJ98L) (Get enough cards for the number of Pis, Get the biggest cards you can afford)

**This is without a doubt an expensive project**, however in my eyes
it's the cost of another server 😂 and the best part about this
project is **you can add to the cluster over time** spreding the cost
which is how I managed to purchase all the hardware. A suggestion
would be to **buy equipment that allows you room to grow** so an 8 port
PoE switch instead of a 4 port if you know you will scale to 8
nodes

If you build this then you can safely say another server is not
needed. This cluster should be more than capable to serve all your
home needs even if you only have 2 nodes. Put it this way, if you
have 4 8GB nodes then you have a combined total of:
* 32GB of RAM
* 16 physical CPU cores @ 1.5GHz

#### **Money Saving Tips**
* Just get 1-2 nodes to start
* cut PoE and use normal power cables
* Use Raspberry Pis with less memmory eg 4GB
* Grab a really cheap case or make one using [these](https://www.amazon.co.uk/dp/B091KJNZLB/)
* Use smaller SD Cards try not to go below 32GB (Reccomended 64GB If money saved elsewhere)

## **BUILD TIME !!**
Pull yourself up by your bootstraps were jumping into this one
runnig 💨

### **Image the SD Cards**
So interesting fact the CPUs used in the raspberry pi 4 use an ARM64
archetecture. When looking for images of Raspbian you will only find
32bit variants which will work however will not make use of all the
hardware which is just a waste. 64bit images exist however are well
hidden, Dont fear 😨 **you can download the latest images from the 
[raspberrypi.org index](https://downloads.raspberrypi.org/raspios_arm64/images/)**

To write the cards I use the [**Raspberry Pi imager**](https://www.raspberrypi.com/software/).
once you have **rpi-imager** installed and you have the 64bit raspbian
image, open ```sudo rpi-imager``` and on the "CHOOSE OS" section go to
the bottom and select use custom image.

> We dont need to unzip the file as the tool is clever enough to
handle that for us

**Before removing the SD card, mount the boot partition - usually the
first partition, look for a file called cmdline.txt - and create an
empty file called ssh** ```sudo touch ssh``` this basically enables
SSH on the Pis first boot allowing us to access the Pis in a totally
headless manner.

### Assemble the cluster
So assembly is very dependant on the kit you bought, and more
often than not the stuff needed here comes with instructions or is
self explanitory. So go ahead and assemble the cluster 🛠

**There is an order of operations that I reccomend:**
* Install PoE hats onto the Pis
* Install the SD Cards into the Pis
* Assemble the case and install Pis
* plug in ethernet cables

**Now allow the Pis to boot for a few minutes so it can resize the


### **Sort out the Network bits**
This is the easy part, there are two methods you can use to set a
static IP address, one is on your DHCP server and the other is on
the device itself. Personally I prefer to set static IPs on the
device itself so I will cover that here.

To find the current ip of your Pis you can go to your DHCP server
and look for the DHCP leases for the Pis.

> there are naming conventions for naming primary and secondary
things but this is your cluster so be creative with it, I have my 
primary node named ```Goob``` and the secondary nodes named ```Doris1```
```Doris2``` and ```Doris3```
[reference](https://www.youtube.com/watch?v=oFb7FVe8sdQ)

**SSH to the Pi** then open and edit the following files
* /etc/hosts
    * edit this line with your hostname: ```127.0.1.1  goob```
* /etc/hostname
    * edit this file with your hostname: ```goob```
* /etc/dhcpcd.conf
    * knowing we will be using only static IPs here I delete
    everything in the file add the following
    *   ```
        interface eth0
        static ip_address=10.10.10.20/24
        static routers=10.10.10.1
        static domain_name_servers=10.10.10.1
        ```
**Now reboot the pi** ```sudo shutdown -r now```

**Once the Pis are back up log into each one and change the default
passwords** you may also want to create a new user for yourself but
thats totally optional.


### **Provision with** ***Ansible***
you want to **create an _Ansible_ control node** and that is as simple as
installing a package onto your machine. _Ansible_ is built using python
which makes it easy to install as **we can use the python pip package
manger.** To check you have it installed do ```pip --version``` if
it's not installed do the following


```curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py```

```python get-pip.py --user```

**once you have pip installed proceed to installing _Ansible_**

[Docs](https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html)

```pip install ansible```

Now that _Ansible_ is installed we can create a runbok that defines the
steps _Ansible_ needs to take on the remote machine to correctly
provision it. This playbook is written in yaml so get ready to make
sure your indents are correct 😬

**Creating the playbook**
now you can copy what I have and it should work - after changing a
thing or two - which is fine however I encourage you to copy what I
have, read the [Docs](https://docs.ansible.com/ansible/latest/user_guide/index.html)
and make any changes you feel are necessary.

> Check the [git repo](https://gitlab.com/AHMZA/pi-docker-swarm-ansible-deploy/-/tree/main) for the most up to date yaml file im using.

**This script assumes you are using SSH keys, which you should but if
not you can skip the whole "Configure SSH" block,**
***I RECCOMEND YOU USE SSH KEYS*** - [read this](https://blog.ahmza.com/posts/securing-ssh/)

**Create the deploy.yml**

```yaml
---
- hosts: piCluster
  become: yes
  tasks:

    - name: Configure SSH
      block:

        - name: Auth local SSH Keys
          ansible.posix.authorized_key:
            user: <pi_user>
            state: present
            key: "{{ item }}"
          with_file:
            - /home/<local_user>/.ssh/id_rsa.pub
            - ./pi_rsa.pub

        - name: Copy SSH Pi Intercoms Private Key
          copy:
            src: ./pi_rsa
            dest: /home/<pi_user>/.ssh/id_rsa
            mode: '0600'
            owner: <pi_user>
            group: <pi_user>

        - name: Copy SSH Pi Intercoms Public Key
          copy:
            src: ./pi_rsa.pub
            dest: /home/<pi_user>/.ssh/id_rsa.pub
            mode: '0644'
            owner: <pi_user>
            group: <pi_user>


    - name: Check for any updates and install them
      apt:
        update_cache: true
        upgrade: dist

    - name: Install Required build dependencies
      apt:
        update_cache: true
        pkg:
          - python3
          - python3-pip
          - vim
          - curl


    - name: Check Docker is installed
      shell: "docker --version"
      register: docker_version

    - name: Install Docker
      block:

        - name: Download Docker script
          command: curl -fsSL https://get.docker.com -o get-docker.sh

        - name: Run Docker install script
          command: sudo sh get-docker.sh

        - name: Enable docker service
          service:
            name: "{{ item }}"
            enabled: true
            state: started
          loop:
            - docker
            - containerd

        - name: Add user to docker group
          user:
            name: <pi_user>
            groups: docker
            append: yes

      when: docker_version.stdout.find('Docker version')


    - name: check Docker compose is installed
      shell: "docker-compose --version"
      register: dc_version

    - name: Install docker compose
      command: sudo pip3 -v install docker-compose
      when: dc_version.stdout.find('docker-compose version')


    - name: wait for network on boot
      command: raspi-config nonint do_boot_wait 0

    - name: Reboot
      reboot:
```

The steps this playbook takes are as follows:
1. Copy your SSH keys to the pi authorized_keys
2. Copy same Pi ssh key between the Pis for intercommunication
3. Check for and Install updates
4. Install any build dependancies
5. Check if Docker is Installed
    * Download the Docker Script
    * Install Docker from script
    * Enable the Docker service
    * Add user to Docker group
6. Check if docker-compose is installed
    * Install docker-compose (This will take a while on each pi so be patient, grab a coffee)
9. Change raspi config to wait for network before boot
10. Reboot

take some time to read through the playbook, read the docs and try to
understand whats going on. Change the usernames to your username.

**Make the hosts file in the same directory as the deploy.yml**
``` yaml
[piCluster]
10.10.10.20
10.10.10.21
10.10.10.22
```
* `[piCluster]` - specifies a group of hosts
* `10.10.10.xx` - specifies the Pis IP 

**create the Pi Intercommunication keys**
``` bash
ssh-keygen
Enter file in which to save the key (/home/ahmza/.ssh/id_rsa): .pi_rsa
```
* save the keys in the same directory the deploy.yml file is

**heres the command to run the playbook.**

`ansible-playbook -i hosts -kK deploy.yml -c paramiko`

* `ansible-playbook` - the command to run the playbook
* `-i hosts` - specifies the host/inventory file
* `-kK` - asks you for password for the SSH connection(-k) and the sudo password(-K)
* `deploy.yml` - the _Ansible_ playbook
* `-c paramiko` - Use the paramiko connection method, I found this works best with ssh keys

You can do so much with _Ansible_, for example mount network shares etc,
if you can do it in the cli you can do it in _Ansible_ !!

Now that the _Ansible_ script is done we can go ahead and actually
configure all the Pis into the cluster.

### **Creating/Joining the swarm**
Creating and joining the cluster is easy - It is manual and tedious so
this is something you could impliment into the ansible playbook using
multiple host groups.

**Follow these steps to create the swarm:**
1. ssh to the main Pi, this will be the manager node.
2. run `docker swarm init`
    * This will return a command and token. Make sure to copy them
3. exit the main Pi
4. ssh to one of the worker nodes
5. paste and run the copied command
6. do the same on the remaining worker nodes

You should now have a correctly configured cluster !!

### **Optional Step - Portainer**
Portainer is a webgui that will allow us to manage the cluster, it will
make deploying and destroying containers across the cluster a breeze.
I do understand that all of what portainer does can simply be accomplished
in the command line, however portainer just makes it less hastle to manage.

**Install Portainer**

Firstly we want to download the yaml file that will be used to deploy
the portainer contiainer on our cluster.

`curl -L https://downloads.portainer.io/portainer-agent-stack.yml -o portainer-agent-stack.yml`

Now we can actually deploy portainer to the cluster using the following
command:

`docker stack deploy -c portainer-agent-stack.yml portainer`

Once the stack is up and running navigate to:

`https://raspberry-ip:9443`

where raspberry-ip is the IP address of the manager node in the swarm.

### **Optional Step - Private Registry**

If you intend to build any of your own docker images then it may be useful
to create a private repository to host any images that you need to run
across the cluster.

to create this private repository create a file called docker-compose.yml
in a folder called repository or whatever and enter the following.
``` yaml

version: '3.9'
services:
  registry:
    image: registry:2
    ports:
      - 5000:5000
    volumes:
      - /home/<pi-user>/docker/registry/data:/var/lib/registry
```

**Be sure to change pi-user to your pi user**

**create a file /etc/docker/daemon.json and eter the following**
``` json
{
    "insecure-registries": ["localhost:5000", "<pi-address>:5000"]
}
```
where `pi-address` is the ip address of the main swarm node.

**restart the docker service with `sudo systemctl restart docker`**

now we need to deploy the registry to the stack like we did with portainer

`docker stack deploy -c docker-compose.yml registry`

and we should have a private registry setup that we can use to push our
custom docker images to.

## **Conclusion**
Well done, you have successfully setup a docker swarm cluster on a bunch
of Pis and along the way you managed to learn a bit about SSH, Ansible,
docker-compose, yaml and networking on Pis. The next step would be to
setup a few containers but I'll leave that to you, dont be affraid to
play around and even ruin the cluster, you can always rebuild it so have
fun 😊