k3s-ssh-service-demo

Summary

A demo of a k3s cluster running pods accessible via ssh and with distinct IPs or names. This code is derived from an example provided by Jérôme Petazzoni.

Basic Setup of k3s

Install a brand new k3s on the target machine using the curl method

curl -sfL https://get.k3s.io | sh -

Apply the settings and run the service

Either apply all configuration files at once via calling it for the directory config

kubectl apply -f config

or apply the settings file by file by issuing the following commands:

sudo kubectl apply -f pvc.yaml 
sudo kubectl apply -f configmap.yaml 
sudo kubectl apply -f service.yaml 
sudo kubectl apply -f pod.yaml

Check for Success

You can check the success by running

sudo kubectl get pod shpod
sudo kubectl describe configmaps shpod

an log into the container as root via

sudo kubectl exec -it shpod -- /bin/sh

If logged in, you get a prompt and can see that the mounting points are available

/ # cat /home/user/.ssh/authorized_keys 
ssh-ed25519 AAAAC3NzaC1lZDI1NTEXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX+qzZ numer@pc-001
/ # ifconfig
eth0      Link encap:Ethernet  HWaddr F6:BB:D9:DC:BE:4B  
          inet addr:10.42.0.10  Bcast:10.42.0.255  Mask:255.255.255.0
          inet6 addr: fe80::f4bb:d9ff:fedc:be4b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1
          RX packets:924 errors:0 dropped:0 overruns:0 frame:0
          TX packets:636 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:4541612 (4.3 MiB)  TX bytes:45948 (44.8 KiB)

# ... lo skipped ...
/ # ps -ef | grep ssh
    1 root      0:00 sshd: /usr/sbin/sshd -D -e [listener] 0 of 10-100 startups

Setting up port forwarding

If you only want to connect from the host, it suffices to execute

$ sudo kubectl port-forward service/shpod 2222:22
Forwarding from 127.0.0.1:2222 -> 22
Forwarding from [::1]:2222 -> 22

To connect from another machine in the network, one must use a more permissive filter for port forwarding:

sudo kubectl port-forward --address 0.0.0.0 service/shpod 2222:22

Use a dedicated IP address

Former versions of service.yaml contained type: LoadBalancer for the pod to obtain an external IP address. This was later changed to using externalIPs directly. You can query the IP via

sudo kubectl describe services shpod

Starting and Stopping the Service

While doing changes or experiments to the service configuration, you can turn off and on the service using the following commands:

sudo kubectl delete services shpod
sudo kubectl apply -f config/service.yaml

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