Skoupidia

Your home machine learning cluster made from rubbish and things found 'round the house.

1. Create A Kubernetes Cluster
2. Install Kubeflow
3. My Own Personal Setup
4. References

Create A Kubernetes Cluster

Create Autobot User

On each of the servers, create a user named autobot. This will be the user ansible will use to install and remove software:

sudo adduser autobot
sudo usermod -aG sudo autobot

Autobot has now been added to the sudo group, but to make ansible less of a pain, remove the need to interactively type the password every time autobot changes to run a command as root.

sudo su
echo "autobot ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers.d/peeps

Generate an SSH key locally

You can do this a number of ways, but here is an easy version:

ssh-keygen -f ~/.ssh/home-key -t rsa -b 4096

or you can use the premade task

make ssh_keys

This will, by default save the public and private keys into your ~/.ssh directory.

We want to take the .pub (public) key from our local server, and add the contents of the pub key to the file ~/.ssh/authorized_keys on each of the servers in the autobot users home directory.

This will allow your local machine (or any machine that has the private key) to be able to automatically login to any of the nodes without typing a password. Again this will be very helpful when running the ansible scripts.

One way to do this is to copy the file contents to the clipboard:

xclip -selection clipboard < ~/.ssh/home-key.pub

Then ssh into the machine as user autobot, and paste the clipboard contents into the ~/.ssh/authorized_keys file (or create the file if it doesn't already exist).

Run Ansible Setups

We should now be ready to run the anisble code.

The Anisble scripts will install some prerequisites, docker, and kubeadm and kubectl on the master and the worker nodes.

Follow along with the README in the ansible directory to continue.

Few Difficult to Script Tasks

Now that ansible had run completely, we need to do a few manual steps. Don't skip these!

You'll need to run these commands on all the nodes (master and workers). After ansible has finished without error.

sudo su
systemctl stop containerd
rm /etc/containerd/config.toml
# it's ok if that errors --^
containerd config default > /etc/containerd/config.toml

You'll need to use a text editor and set a value from false to true.

Edit the file /etc/containerd/config.toml, and change the setting SystemdCgroup = false to SystemdCgroup = true in the section:

...
[plugins."io.containerd.grpc.v1.cri".containerd.runtimes.runc.options]
    ...
    SystemdCgroup = true
...

---

Note: Adding GPUs to the config.toml https://github.com/NVIDIA/k8s-device-plugin#quick-start

---

This will enable the systemd cgroup driver for the containerd container runtime.

systemctl restart containerd

Run the following to pull down needed configurations for kubeadm

kubeadm config images pull

Run Kube Init

Now, only on the designated master node, run

kubeadm init --v=5

If all goes well, the output of this command will give use the commands we can use on the worker nodes to join the cluster.

For example:

kubeadm join 192.168.1.15:6443 --token 3e...l --discovery-token-ca-cert-hash sha256:65...ec 

Save copy this command as we'll use this on the worker nodes to have the nodes join the master node.

It's a good idea to add the kube config to the autobot user so you can do things like kubectl get nodes. Run these as the autobot user:

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Join Workers to Cluster

On each worker nodes run the join command (note your values will be slightly different)

kubeadm join 192.168.1.15:6443 --token 3eo...6il --discovery-token-ca-cert-hash sha256:92a23........e9dee765ec

Cluster Networking Using Calico

After the workers have joined the cluster, we should be able to see them:

autobot@kmaster:~$ kubectl get nodes
NAME       STATUS     ROLES           AGE     VERSION
kmaster    NotReady   control-plane   77m     v1.28.6
kworker1   NotReady   <none>          25m     v1.28.6
kworker2   NotReady   <none>          3m34s   v1.28.6

But we need to add container networking before they will be in the ready state

kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.26.1/manifests/calico.yaml

(or use the version in the repos ./kubernetes/ folder)

After applying calico, give the cluster some time to get all the node into the ready state.

autobot@kmaster:~$ kubectl get nodes -w
NAME       STATUS   ROLES           AGE   VERSION
kmaster    Ready    control-plane   91m   v1.28.6
kworker1   Ready    <none>          40m   v1.28.6
kworker2   Ready    <none>          17m   v1.28.6

We now have a working cluster!

Add MetalLB

Kubernetes only really works correctly with an external load balancer that feeds it IPs. Without that it's difficult to run several workloads on the cluster - for example, there is only one port 80.

MetalLB runs inside of Kubernetes and pretends to be a load balancer. It's great.

For up to date info see here: https://metallb.org/installation/ but in summary, we are going to install the load balancer:

kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/v0.13.12/config/manifests/metallb-native.yaml

After it is installled, we need to configure what IP addresses it gives out. We'll associate our local IP pool to the local load balancer by editing an applying ./kubernetes/metallb_stage2.yaml.

Add Some Storage

There are many ways to add storage to the cluster. For something more than just playing around in a home lab, have a look into Minio. Minio creates a local storage system that is S3 compatible. This will allow any pod to use the storage. We'll actually set that up later. Here though, we are just using local disk storage.

This is quite specific to how you have disks setup, but here is an example on mine. I have an external USB drive plugged into the master node. It is already formatted and ready to go. First you need to find which /dev the USB is plugged into, and then you can create a folder and mount it:

lsblk

sudo mkdir /mnt/usbd
sudo mount /dev/sbd1 /mnt/usbd
sudo mkdir /mnt/usbc
sudo mount /dev/sdc1 /mnt/usbc

You should be able to see the contents of the drive now ls /mnt/usbd.

Once you have that working, you can add the listing to the /etc/fstab file so that it will mount again if you reboot the server:

sudo su
echo "/dev/sdb1 /mnt/usbd ext4 defaults 0 0" >> /etc/fstab
echo "/dev/sdc2 /mnt/usbc ext4 defaults 0 0" >> /etc/fstab

With the drive mounted, you can make a PersistentVolume definitions. Have a look at ./kuberenets/oscar/local-pv-volume.yaml for some examples.

Add Labels

You can make sure different pods run on correct nodes by adding a label to the nodes and then using the affinity section of the spec. For example I label my slow drive nodes and the nodes with a gpu like so:

kubectl label nodes kmaster disktype=hdd
kubectl label nodes kworker1 disktype=ssd
kubectl label nodes kworker2 disktype=ssd
kubectl label nodes kworker1 has_gpu=true
kubectl label nodes kworker2 has_tpu=true

---

Note: use accelerator= with a type example-gpu-x100 to mark nodes hardware

---

You can see the labels with

kubectl get nodes --show-labels

Then, when deploying a service, you can do something like:

spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: disktype
            operator: In
            values:
              - hdd

To ensure the pod gets the correct hardware.

Optional - Install Tailscale

(tbd)

curl -fsSL https://tailscale.com/install.sh | sh

Install Kubeflow

(tbd)

My Own Personal Setup

In the folder ./kubernetes/oscar/ you will find the configuration definitions I have for my cluster. You may find them as useful examples.

The first script creates my namespaces. I use tools for things like a Jellyfin media server and science for doing actual ML work.

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/namespaces.yaml

I've already added a mount point on all the nodes for scratch storage (/mnt/kdata). See the local-pv-volume for details. This will let pods claim some of that data.

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/local-pv-volume.yaml

Those storage options get reused once the pod goes down, and are only useful for temporary storage. For longer term storage I have a few USB drives plugged into various nodes. I used these drives for local media for jellyfin, and when downloading / training machine learning models I want to keep around

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/usb-pv-volume.yaml

Deployment of our local media server

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/jellyfin.yaml

Deployment of my custom built Jupyter notebook install.

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/jupyter.yaml

Once installed, you can upload the Verify notebook to make sure your GPU is working.

Create an S3 like (s3 compatible) storage service locally

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/minio.yaml

Once installed, you can upload the Verify notebook to make sure storage is working.

You can also install the CLI client on your workstations to interact with the buckets:

curl https://dl.min.io/client/mc/release/linux-amd64/mc --create-dirs -o $HOME/bin/mc
chmod u+x $HOME/bin/mc
mc --help

Example usage:

mc alias set oscar http://192.168.1.23:80 minio minio123  # setup the client
mc admin info oscar
mc mb oscar/test-bucket
mc ls oscar

This a just a utility I made to generate random MIDI files for musical inspiration and to feed into some models I am playing with (probably not interesting)

kubectl apply -f https://raw.githubusercontent.com/robrohan/skoupidia/main/kubernetes/oscar/songomatic.yaml

If a volume ever gets stuck, and you want to allow others to claim it, you can un-taint it like this:

kubectl patch pv usb-jelly-1-pv-volume -p '{"spec":{"claimRef": null}}'

Troubleshooting

DNS

This is can be quite frustrating. I think this is just an Ubuntu thing. Inside a worker node, it will use the master node for DNS. The master node will look inside itself to resolve the DNS entry, but if it doesn't know the URL, it'll look in /etc/resolv.conf for a name server.

There are seemingly several process that overwrite that file from time to time which seems to kill resolution. The netplan process, resolvd process, and tailscale can over write it too. This is the process I've found that works, but if it gets to be too much of a problem, you can unlink the /etc/resolv.conf file and just edit it.

On kmaster node:

sudo vi /etc/systemd/resolved.conf

sudo unlink /etc/resolv.conf
sudo ln -sf /run/systemd/resolve/resolv.conf /etc/resolv.conf
sudo systemctl restart systemd-resolved
sudo systemctl enable systemd-resolved

sudo cat /etc/resolv.conf

References

• Build a Kubernetes Home Lab from Scratch step-by-step!
• How to Install Containerd Container Runtime on Ubuntu 22.04
• How to with new stuff
• Local kubectl access