Configuring Kubernetes cluster using tinkerbell

This repository contains an example tinkerbell (https://tinkerbell.org/) workflow for provisioning k8s control plane and worker nodes on top of the raspberries pi version 4 (RPi4).

Introduction:

Tinkerbell is engine for provisioning bare metal servers, it helps users to build fully bootable and operational machine from scratch. It can be used for any type of the machine from traditional x86_64 servers to arm based single-board computers. This repository contains step by step instruction, how leverage tinkerbell provisioning engine to build fully operational k8s cluster. It is assumed some familiarity with tinkerbell concepts in the below instruction.

Preparation:

Setting local environment

In order to install tinkerbell locally we need to setup a virtual machine or a dedicated bare metal server. In the presented example the following setup was created:

The lab consist of:

KVM+QEMU hypervisor running on top of fedora 31
Centos 7 virtual machine hosting tinkerbell provisioner
Raspberries Pies version 4 workers

Configure hypervisor network

In order to ensure flawless communication between RPi4 - host- vm, it is required to first setup a bridge in the host. In the fedora31 it can be achieved as follows:

sudo nmcli con add ifname packet type bridge con-name packet
sudo ip addr add <ip addr> dev packet
sudo ip link  set up dev packet
sudo nmcli con add type bridge-slave ifname <hv lan interface> master packet
sudo sysctl -w .net.ipv4.conf.packet.bc_forwarding=1
sudo sysctl -w net.ipv4.ip_forward=1
sudo sysctl -w net.bridge.bridge-nf-call-iptables=0

Note: Adjust the above configuration to your host. The listed kernel parameters are used to allow forwarding of dhcp request to virtual machine.

Create virtual machine

Ensure virtual machine is connected to the previously created bridge and it does not block traffic for http, https, dhcp, bootpc, tftp, nfs, mountd, rpc-bind.
On centos 7 as root:

firewall-cmd --permanent --add-service nfs3
firewall-cmd --permanent --add-service mountd
firewall-cmd --permanent --add-service rpc-bind
firewall-cmd --permanent --add-service tftp
firewall-cmd --permanent --add-service dhcp
firewall-cmd --permanent --add-port 68/udp
firewall-cmd --permanent --add-service http
firewall-cmd --permanent --add-service https

Optionally if you are planning on making provisioner a gateway for rpi4, configure NAT:

sysctl -w net.ipv4.ip_forward=1
firewall-cmd --permanent --direct --passthrough ipv4 -t nat -I POSTROUTING -o eth0 -j MASQUERADE -s <rpi4 subnet>
firewall-cmd --reload

Prepare raspberries pies

Take them out of the box.

Installation and configuration of the provisioner and RPi4

Install tinkerbell

Connect to the virtual machine and follow steps from https://tinkerbell.org/setup/packet-with-terraform/provisioner/ . At the end of installation, envrc file should be created, note its location.
Replace vmlinuz-aarch64 and initramfs-aarch64 with the ones from:

wget -O /var/tinkerbell/nginx/misc/osie/current/vmlinuz-aarch64  https://storage.googleapis.com/rpi4-uefi-tinkerbell/vmlinuz-aarch64
wget -O /var/tinkerbell/nginx/misc/osie/current/initramfs-aarch64 https://storage.googleapis.com/rpi4-uefi-tinkerbell/initramfs-aarch64

It is a custom build kernel and initramfs for rpi4 to execute a workflow. The difference from the standard osie, is that workflow is directly executed in the initramfs stage. The kernel was build to execute workflow contained in this repository, it is possible it won't work with other workflows.

Raspberry Pi

Install rpi4 uefi (https://rpi4-uefi.dev/) onto sd card, use the prepared image:

wget -O rpi4-uefi.img https://storage.googleapis.com/rpi4-uefi-tinkerbell/rpi4-uefi.img
dd if=worker/rpi4-uefi.img of=/dev/mmcblk0 #replace it according to your sd card device

When booting rpi4 for the first time you have to change boot order to boot from pxe.

Note: If you decide to use upstream rpi4-uefi image, make sure that it is using device tree. The option in question can be found in the uefi menu under: Device Manager → Raspberry Pi Configuration → Advanced Configuration

Configure workflows

Workflow is a set of task which are executed in order and are used to configure the bare metal machine. Each of the task is executed in th separate docker container. All task are supervised by a tink-worker, which gathers logs, communicates with external services and handles errors.

Prepare workflow

Since workflows are executed in-memory on raspberry pi, it is required to ensure tink-worker and fluent-bit support that architecture, at the time of writing tink-worker was not available, but we prepared one for you, you can pull it from here:

docker pull ottovsky/tink-worker:armv7-latest
docker pull fluent/fluent-bit:arm32v7-1.3.8

Once pulled, tag it with your ${TINKERBELL_HOST_IP} registry and push it:

docker tag ottovsky/tink-worker:armv7-latest ${TINKERBELL_HOST_IP}/tink-worker:armv7
docker tag fluent/fluent-bit:arm32v7-1.3.8  ${TINKERBELL_HOST_IP}/fluent-bit:1.3-arm
docker push ${TINKERBELL_HOST_IP}/tink-worker:armv7
${TINKERBELL_HOST_IP}/fluent-bit:1.3-arm

Next follow instructions from workflow directory.

Create workflow

Source envrc

cat templates/hw.json | envsubst UUID="$(uuidgen)" IP="<desired ip>" MASK="255.255.255.0" GW="<desired gw ip>" MAC="<mac of RPi>" HOSTNAME="<desire hostname>" > device.json
docker cp device.json deploy_tink-cli_1:/root
docker exec -ti deploy_tink-cli_1 tink hardware push --file /root/device.json

Example output after all RPi were registered:

 docker exec -ti deploy_tink-cli_1 tink hardware all
 {"id": "5156f2b7-b0bc-403d-a3f7-5a2db8a40918", "arch": "aarch64", "hostname": "master-1", "allow_pxe": true, "ip_addresses": [{"address": "192.168.2.35", "netmask": "255.255.255.0", "address
 _family": 4}], "network_ports": [{"data": {"mac": "dc:a6:32:7a:28:91"}, "name": "eth0", "type": "data"}], "allow_workflow": true}
 {"id": "e247beba-0a29-4f76-91f5-c74e89b8b74d", "arch": "aarch64", "hostname": "worker-1", "allow_pxe": true, "ip_addresses": [{"address": "192.168.2.36", "netmask": "255.255.255.0", "address
 _family": 4}], "network_ports": [{"data": {"mac": "dc:a6:32:7a:2a:65"}, "name": "eth0", "type": "data"}], "allow_workflow": true}
 {"id": "9f26de7a-3149-4833-a453-8a73e95a1d53", "arch": "aarch64", "hostname": "worker-2", "allow_pxe": true, "ip_addresses": [{"address": "192.168.2.37", "netmask": "255.255.255.0", "address
 _family": 4}], "network_ports": [{"data": {"mac": "dc:a6:32:7a:29:e1"}, "name": "eth0", "type": "data"}], "allow_workflow": true}

Note: "facility_code": "onprem initrd=initramfs-aarch64 #" is a workaround to disable console and to ensure proper boot of kernel. We are leveraging the absence of sanity check in the boots component: https://github.com/tinkerbell/boots/blob/master/installers/osie/main.go#L90 .

Create templates

export SSID=<wifi ssid>
export PSK=<wifi psk>
export COUNTRY=<wifi country>
export SECRET=<k8s secret>
export K3S="https://<master ip>:6443 
cat templates/workflow-master.tmpl | envsubst > k8s-master.tmpl
cat templates/workflow-worker.tmpl | envsubst > k8s-worker.tmpl
docker cp k8s-master.tmpl deploy_tink-cli_1:/root
docker cp k8s-worker.tmpl deploy_tink-cli_1:/root
docker exec -ti deploy_tink-cli_1 tink template create -n k8s-master -p /root/k8s-master.tmpl
docker exec -ti deploy_tink-cli_1 tink template create -n k8s-worker -p /root/k8s-worker.tmpl

Note down the returned ids of the templates.
Example output of created templates:

docker exec -ti deploy_tink-cli_1 tink template list
+--------------------------------------+---------------+-------------------------------+-------------------------------+
| TEMPLATE ID                          | TEMPLATE NAME | CREATED AT                    | UPDATED AT                    |
+--------------------------------------+---------------+-------------------------------+-------------------------------+
| 4c4deca8-7e80-4518-9729-4874a166a729 | k8s-master    | 2020-05-07 08:07:31 +0000 UTC | 2020-05-07 08:07:31 +0000 UTC |
| b6fa353b-d20e-434d-9652-4ebe5231257b | k8s-worker    | 2020-05-07 08:05:57 +0000 UTC | 2020-05-07 08:05:57 +0000 UTC |
+--------------------------------------+---------------+-------------------------------+-------------------------------+

Create workflows, in orderd to this, it is required to assign template id with target id.
```
docker exec -ti deploy_tink-cli_1 tink workflow create -t <template id> -r '{"device_1": "<ip of the taget device>"}'
```
In this step, you decide what role should be assigned to RPi. for example if you would like one RPi to be k8s master, you have to assign targeted hardware IP to the k8s-master template. Note down the workflow ids.

Execute workflow

Insert empty sd card to the raspberry pi and power it up. Wait till the workflow is executed:

docker exec -ti deploy_tink-cli_1 tink workflow events <workflow id> 
+--------------------------------------+------------------+--------------+----------------+---------------------------------+--------------------+
| WORKER ID                            | TASK NAME        | ACTION NAME  | EXECUTION TIME | MESSAGE                         |      ACTION STATUS |
+--------------------------------------+------------------+--------------+----------------+---------------------------------+--------------------+
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | disk-wipe    |              0 | Started execution               | ACTION_IN_PROGRESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | disk-wipe    |             11 | Finished Execution Successfully |     ACTION_SUCCESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | os-install   |              0 | Started execution               | ACTION_IN_PROGRESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | os-install   |            501 | Finished Execution Successfully |     ACTION_SUCCESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | os-configure |              0 | Started execution               | ACTION_IN_PROGRESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | os-configure |              3 | Finished Execution Successfully |     ACTION_SUCCESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | install-k8s  |              0 | Started execution               | ACTION_IN_PROGRESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | install-k8s  |             19 | Finished Execution Successfully |     ACTION_SUCCESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | reboot       |              0 | Started execution               | ACTION_IN_PROGRESS |
| 5156f2b7-b0bc-403d-a3f7-5a2db8a40918 | k8s-installation | reboot       |             14 | Finished Execution Successfully |     ACTION_SUCCESS |
+--------------------------------------+------------------+--------------+----------------+---------------------------------+--------------------+

Once the workflow finished, the RPi should be an operational k8s master/worker node.

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