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Concepts

Nodefilters

About

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

Syntax

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

Example

  • 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="[email protected]:0"
    • Looking at --k3s-arg="[email protected]: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
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