Concepts

Nodefilters

Nodefilters are a concept in k3d to specify which nodes of a newly created cluster a condition or setting should apply to.

The overall syntax is @<group>:<subset>[:<suffix].

@ denotes the start of a nodefilter in a k3d flag value
<group> denotes the node group you want to filter in
- one of server, servers, agent, agents, loadbalancer, all
  - note, that all also includes the cluster-external server loadbalancer (k3d-proxy container)
<subset> denotes the subset of the chosen group you want to apply the flag to
- wildcard *: all nodes in that group
- index, e.g. 0: only the first node of that group
- list, e.g. 1,3,5: nodes 1, 3 and 5 of that group
- range, e.g. 2-4: nodes 2 to 4 of that group
<suffix> (optional) can hold some flag specific configuration
- e.g. for the --port flag this could be direct or proxy (default) to configure the way of exposing ports

Problem: You want to have Nginx as your ingress controller, but by default, K3s deploys Traefik.
Solution: Disabling the default Traefik deployment using K3s’ --disable=traefik flag.
Note: It’s enough to do this on the first (initializing) server node.
How-To: k3d cluster create notraefik --k3s-arg="--disable=traefik@server:0"
- Looking at --k3s-arg="--disable=traefik@server:0", everything after the @ sign is part of the nodefilter.
  - server is the node group: server nodes
  - after the : follows the subset, which in this case is the index 0: the first server node to be created (k3d-notraefik-server-0)

Last update: December 11, 2021