K3s is a low resource version of Kubernetes (k8s). https://k3s.io In k8s is possible to have a cluster with more server nodes in case that one of the main server nodes will fail, another one can take his job.
Can I do the same with k3s? and how?
In k3s, you usually start to create server node with this command:
k3s server
which will generate a unique token for adding more agent nodes.
k3s agent --server https://myserver:6443 --token ${NODE_TOKEN}
but what if I want to add another server node, not just agent?
As of v1.0 yes it is possible and they showed it running in a webinar using an external MySQL database as datastore.
You're asking for High-Availability ("HA") support. Or, if you really aren't, the functionality you described will only be provided as part of HA support. Right now, sqlite is used as the data storage system, which does not allow for more than one server. This is referenced vaguely in the readme. There's a couple issues in the github repo for tracking this (such as this one), but there's been various references in the Slack to things that haven't been posted in the issues, so I'm not sure what the current status is, or where you can go to get updates.