Pi Cluster Documentation

Ansible Control Node

A Virtual-BOX VM running on a Windows PC is used as Ansible Control Node, pimaster for automating the provisioning of the Raspberry PIs cluster.

As OS for pimaster a Ubuntu 20.04 LTS server will be used.

Installing Docker

Docker is used by Molecule, Ansible’s testing tool, for building the testing environment, so it is needed to have a Docker installation on the Control Node for developing and testing the Ansible Playbooks/Roles.

Follow official installation guide.

  • Step 1. Uninstall old versions of docker

    sudo apt-get remove docker docker-engine docker.io containerd runc

  • Step 2. Install packages to allow apt to use a repository over HTTPS

    sudo apt-get update

sudo apt-get install \
apt-transport-https \
ca-certificates \
curl \
gnupg \
lsb-release

  • Step 3. Add docker´s official GPG key

    curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

  • Step 4: Add x86_64 repository

    echo \
  "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

  • Step 5: Install Docker Engine

    sudo apt-get install docker-ce docker-ce-cli containerd.io

  • Step 6: Enable docker management with non-priviledge user

    • Create docker group

      sudo groupadd docker

    • Add user to docker group

      sudo usermod -aG docker $USER

  • Step 7: Configure Docker to start on boot

    sudo systemctl enable docker.service
sudo systemctl enable containerd.service

  • Step 8: Configure docker daemon.

    • Edit file /etc/docker/daemon.json

      Set storage driver to overlay2 and to use systemd for the management of the container’s cgroups. Optionally default directory for storing images/containers can be changed to a different disk partition (example /data). Documentation about the possible options can be found here

      {
    "exec-opts": ["native.cgroupdriver=systemd"],
    "log-driver": "json-file",
    "log-opts": {
    "max-size": "100m"
    },
    "storage-driver": "overlay2",
    "data-root": "/data/docker"  
}

    • Restart docker

      sudo systemctl restart docker

Installing KVM and Vagrant

In order to automate the testing of some of the roles that requires a VM and not a docker image (example: Storage roles), KVM and Vagrant will be installed

Enable nested virtualization within the VM

Need to be changed with the command line. Not supported in GUI

vboxmanage modifyvm <pimaster-VM> --nested-hw-virt on

KVM installation in Ubuntu 20.04

  • Step 1. Install KVM packages and its dependencies

    sudo apt install qemu qemu-kvm libvirt-clients libvirt-daemon-system virtinst bridge-utils

  • Step 2. Enable on boot and start libvirtd service (If it is not enabled already):

    sudo systemctl enable libvirtd
sudo systemctl start libvirtd

  • Step 3. Add the user to libvirt group

    sudo usermod -a -G libvirtd $USER

Vagrant installation in Ubuntu 20.04

  • Step 1. Add hashicorp apt repository

    curl -fsSL https://apt.releases.hashicorp.com/gpg | sudo apt-key add -
sudo apt-add-repository "deb [arch=amd64] https://apt.releases.hashicorp.com $(lsb_release -cs) main"
sudo apt-get update

  • Step 2. Install vagrant

    sudo apt install vagrant

Install vagrant-libvirt plugin in Linux

In order to run Vagrant virtual machines on KVM, you need to install the vagrant-libvirt plugin. This plugin adds the Libvirt provider to Vagrant and allows Vagrant to control and provision machines via Libvirt

  • Step 1. Install dependencies

    sudo apt install build-essential qemu libvirt-daemon-system libvirt-clients libxslt-dev libxml2-dev libvirt-dev zlib1g-dev ruby-dev ruby-libvirt ebtables dnsmasq-base libguestfs-tools

  • Step 2. Install vagrant-libvirt plugin:

    vagrant plugin install vagrant-libvirt

  • Step 3. Install mutate plugin which converts vagrant boxes to work with different providers.

    vagrant plugin install vagrant-mutate

Installing Ansible and Molecule testing environment

Ansible can be installed in Ubuntu 20.04 using official package from the ansible repository ‘sudo apt install ansible’ will install an old ansible verion.

Ansible Molecule is not available as official package, so pip is the only alternative Instead, install latest version for python3 with python package manager pip.

Python Ansible and Molecule packages and its dependencies installed using Pip might conflict with python3 packages included in the Ubuntu official release, so packages installation should be done using non-root user (local user packages installation) or within a python virtual environment.

Installation of the whole Ansible environment can be done using a python virtual environment.

  • Step 1. Install python Virtual Env and Pip3 package

    sudo apt-get install python3-venv python3-pip

  • Step 2. Create Virtual Env for Ansible

    python3 -m venv ansible

  • Step 3. Activate Virtual Environment

    source ansible/bin/activate

  • Step 4. Upgrade setuptools and pip packages

    pip3 install --upgrade pip setuptools

  • Step 5. Install ansible

    pip3 install ansible

  • Step 6. Install yamllint, ansible-lint and jmespath (required by ansible json filters)

    pip3 install yamllint ansible-lint jmespath

  • Step 7. Install Docker python driver and molecule packages:

    pip3 install molecule[docker]

  • Step 8. Install molecule vagrant driver

    pip3 install molecule-vagrant python-vagrant

Create public/private SSH key for remote connection users

ansible unix user will be created in all servers with root privileges (sudo permissions) so Ansible can automate the configuration process (use as ansible_remote_user when connecting).

For connecting to the servers from my Windows laptop using SSH client (Putty), oss, UNIX user (with sudo privileges) will be used. In order to improve security, default ubuntu UNIX user created by cloud images will be disabled.

ssh private/public keys for both users need to be generated once, and public ssh key can be copied automatically on all servers of the cluster to enable passwordless SSH connection. Those users and its public keys will be added to cloud-init configuration (user-data), when installing Ubuntu OS.

Create SSH keys

Authentication using SSH keys will be the only mechanism available to login to the server. We will create SSH keys for two different users:

  • oss user, used to connect from my home laptop

    For generating SSH private/public key in Windows, Putty Key Generator can be used:

    ubuntu-SSH-key-generation

    Public-key string will be used as ssh_authorized_keys of the default user (ubuntu) in cloud-init user-data

  • ansible user, used to automate configuration activities with Ansible

    For generating ansible SSH keys in Ubuntu server execute command:

    ssh-keygen

    In directory $HOME/.ssh/ public and private key files can be found for the user

    id_rsa contains the private key and id_rsa.pub contains the public key.

    Content of the id_rsa.pub file has to be used as ssh_authorized_keys of the ansible user in cloud-init user-data

    cat id_rsa.pub 
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDsVSvxBitgaOiqeX4foCfhIe4yZj+OOaWP+wFuoUOBCZMWQ3cW188nSyXhXKfwYK50oo44O6UVEb2GZiU9bLOoy1fjfiGMOnmp3AUVG+e6Vh5aXOeLCEKKxV3I8LjMXr4ack6vtOqOVFBGFSN0ThaRTZwKpoxQ+pEzh+Q4cMJTXBHXYH0eP7WEuQlPIM/hmhGa4kIw/A92Rm0ZlF2H6L2QzxdLV/2LmnLAkt9C+6tH62hepcMCIQFPvHVUqj93hpmNm9MQI4hM7uK5qyH8wGi3nmPuX311km3hkd5O6XT5KNZq9Nk1HTC2GHqYzwha/cAka5pRUfZmWkJrEuV3sNAl ansible@pimaster

Install aditional packages

The following packages are also needed:

  • Install Gnu GPG packet. Ansible files encryption

    sudo apt install gnupg

  • Install pwgen to generate random passwords

    sudo apt install pwgen
Last Update: Feb 25, 2022

Comments: