I have had an on/off relationship with Kubernetes for a number of years and want to spend some time really getting to know how to use it, run it and secure it.
I previously wrote some Anisble playbooks to run Kubernetes on my desktop then chatting to @alistair_hey about running a local environment on my fairly underpowered laptop he suggested k3d … so the journey starts here.
Prerequisites
k3d is a wrapper for k3s but runs the cluster in Docker. This means that you will need Docker running on the machine (which I already have!). A quick solution is Docker Desktop which is very accessible or you can install it using the instructions for your OS and Architecture.
I will be using kubectl later to interact with the cluster, so this is also required.
Getting Started
Install kubectl
As I am running on Linux I will use the installation instructions for kubectl
The first step is to pull the latest binary from dl.k8s.io.
cd ~/Downloads
curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
Now I have this, I want to check against the checksum file
cd ~/Downloads
curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
I use the checksums file to validate the binary is as it should be
echo "$(cat kubectl.sha256) kubectl" | sha256sum --check
Assuming I were told it was kubectl: OK I can continue to install.
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
Lets now check the install was good
kubectl version --short=true
which should give me output similar to
Client Version: v1.23.4
Server Version: v1.22.7+k3s1
Installing k3d
First step is to install k3d - I don’t like using wget or curl with install scripts from GitHub so I’m am going to be using the assets from the Releases Page.
I am using Ubuntu on a x64 machine so I need to download k3d-linux-amd64
Note I’m using v5.4.1 at the time of writing
Once I have it downloaded, I can install the command on the path
cd ~/Downloads
sudo install k3d-linux-amd64 /usr/local/bin/k3d
Now it has been installed I can run to check
k3d --version
This should give me the output;
k3d version v5.4.1
k3s version v1.22.7-k3s1 (default)
Creating the first cluster
For the first cluster I am going to create it with the following parameters
- Name: first-cluster
- Servers: 3
To do this, I use the cluster sub command
k3d cluster create first-cluster --servers 3
This will give an output similar to this;
INFO[0000] Prep: Network
INFO[0000] Created network 'k3d-first-cluster'
INFO[0000] Created image volume k3d-first-cluster-images
INFO[0000] Starting new tools node...
INFO[0000] Creating initializing server node
INFO[0000] Creating node 'k3d-first-cluster-server-0'
INFO[0000] Pulling image 'ghcr.io/k3d-io/k3d-tools:5.4.1'
INFO[0001] Pulling image 'docker.io/rancher/k3s:v1.22.7-k3s1'
INFO[0002] Starting Node 'k3d-first-cluster-tools'
INFO[0005] Creating node 'k3d-first-cluster-server-1'
INFO[0006] Creating node 'k3d-first-cluster-server-2'
INFO[0006] Creating LoadBalancer 'k3d-first-cluster-serverlb'
INFO[0007] Pulling image 'ghcr.io/k3d-io/k3d-proxy:5.4.1'
INFO[0009] Using the k3d-tools node to gather environment information
INFO[0009] HostIP: using network gateway 172.20.0.1 address
INFO[0009] Starting cluster 'first-cluster'
INFO[0009] Starting the initializing server...
INFO[0009] Starting Node 'k3d-first-cluster-server-0'
INFO[0010] Starting servers...
INFO[0010] Starting Node 'k3d-first-cluster-server-1'
INFO[0031] Starting Node 'k3d-first-cluster-server-2'
INFO[0047] All agents already running.
INFO[0047] Starting helpers...
INFO[0047] Starting Node 'k3d-first-cluster-serverlb'
INFO[0054] Injecting records for hostAliases (incl. host.k3d.internal) and for 4 network members into CoreDNS configmap...
INFO[0056] Cluster 'first-cluster' created successfully!
INFO[0056] You can now use it like this:
kubectl cluster-info
Within just under a minute I have my first cluster up and running, I can list the clusters to see its running with the cluster list sub command
k3d cluster list
The output tells me that there are 3 servers running;
NAME SERVERS AGENTS LOADBALANCER
first-cluster 3/3 0/0 true
Now that the cluster is running I can use kubectl to get some more information about the cluster
kubectl cluster-info
which should give similar output to this;
Kubernetes control plane is running at https://0.0.0.0:38909
CoreDNS is running at https://0.0.0.0:38909/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Metrics-server is running at https://0.0.0.0:38909/api/v1/namespaces/kube-system/services/https:metrics-server:https/proxy
I know that I have 3 nodes - so lets get some inforamtion about them too
kubectl get nodes
This will give me an output similar to this;
NAME STATUS ROLES AGE VERSION
k3d-first-cluster-server-0 Ready control-plane,etcd,master 15m v1.22.7+k3s1
k3d-first-cluster-server-1 Ready control-plane,etcd,master 15m v1.22.7+k3s1
k3d-first-cluster-server-2 Ready control-plane,etcd,master 14m v1.22.7+k3s1
The last step in this bootstrapping post is to check I can run a container - so I’m going to do a basic command to run a new pod called nginx using the nginx image
kubectl run nginx --image nginx
which hopefully should give me some output letting me know my pod has been created
pod/nginx created
A pod is the smallest instance of compute that can be deployed. A pod can contain a number of containers if their purpose is tightly coupled; an example might be a pod with a cache container that has another short life container required to pre-populate.
I can check the status of the pod using kubectl
kubectl describe pod nginx
Which will give me a verbose output about the pod
Name: nginx
Namespace: default
Priority: 0
Node: k3d-first-cluster-server-2/172.20.0.4
Start Time: Thu, 07 Apr 2022 18:54:28 +0100
Labels: run=nginx
Annotations: <none>
Status: Running
IP: 10.42.2.4
IPs:
IP: 10.42.2.4
Containers:
nginx:
Container ID: containerd://f5f568d6e62b5c8db6742b7ec2136a8939f2deb65e4b68a662a5ee7ee88e94e5
Image: nginx
Image ID: docker.io/library/nginx@sha256:2275af0f20d71b293916f1958f8497f987b8d8fd8113df54635f2a5915002bf1
Port: <none>
Host Port: <none>
State: Running
Started: Thu, 07 Apr 2022 18:54:28 +0100
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-vs2qt (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
kube-api-access-vs2qt:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 5m33s default-scheduler Successfully assigned default/nginx to k3d-first-cluster-server-2
Normal Pulling 5m33s kubelet Pulling image "nginx"
Normal Pulled 5m28s kubelet Successfully pulled image "nginx" in 5.005731925s
Normal Created 5m28s kubelet Created container nginx
Normal Started 5m27s kubelet Started container nginx
I can see from this that the pod was deployed on server-2 and pulled the latest nginx image before successfully starting
Cleaning Up
Now that I know that everything seems to be okay, I can tear it all down before starting to do something more useful in the next blog post.
First lets stop the nginx pod
kubectl delete pod nginx
Then I can stop the cluster
k3d cluster stop first-server
INFO[0000] Stopping cluster 'first-cluster'
INFO[0011] Stopped cluster 'first-cluster'
I am going to keep the cluster for the next blog, but I can now remove it if I wish using
k3d cluster delete first-cluster
INFO[0000] Deleting cluster 'first-cluster'
INFO[0000] Deleting cluster network 'k3d-first-cluster'
INFO[0000] Deleting 2 attached volumes...
WARN[0000] Failed to delete volume 'k3d-first-cluster-images' of cluster 'first-cluster': failed to find volume 'k3d-first-cluster-images': Error: No such volume: k3d-first-cluster-images -> Try to delete it manually
INFO[0000] Removing cluster details from default kubeconfig...
INFO[0000] Removing standalone kubeconfig file (if there is one)...
INFO[0000] Successfully deleted cluster first-cluster!