K3s Version compatibility between master and agent?

[aljohn0422]

Environmental Info: K3s Version:

• Master: k3s version v1.20.0+k3s2 (2ea6b163); go version go1.15.5
• agent: k3s version v1.20.5+k3s1 (355fff30); go version go1.15.10

Node(s) CPU architecture, OS, and Version:

• Master: Linux 5.8.0-44-generic #50~20.04.1-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux
• agent: Linux 4.9.201-tegra #1 SMP PREEMPT aarch64 aarch64 aarch64 GNU/Linux (Jetson Xavier NX on Jetpack 4.5)

Cluster Configuration: 1 server with 6 other running agents on other devices (including a Jetson Nano, but no other Jetson devices.)

Describe the bug: Cannot connect this agent to master. Installation script ran without any issue. But this machine is not listed in sudo k3s kubectl get node.

Steps To Reproduce:

• Installed latest K3s: curl -sfL https://get.k3s.io | K3S_URL=<server ip> K3S_TOKEN=<server token> sh -s - --docker
• check on master node: sudo k3s kubectl get node

Expected behavior: K3s agent successfully connected to master.

Actual behavior: This machine is not listed when I run sudo k3s kubectl get node on master.

Additional context / logs: When I set export INSTALL_K3S_VERSION=v1.20.0+k3s2 to install older k3s version, the agent connected successfully. It just won't connect on the latest version which is v1.20.5+k3s1.

Master is on version v1.20.0+k3s2. I have other agent nodes running on v1.20.2+k3s1, v1.20.4+k3s1, v1.20.0+k3s2 without a problem.

[brandond]

In general, the Kubernetes version skew policy applies: https://kubernetes.io/docs/setup/release/version-skew-policy/

In short, servers can be newer than agents, but agents should not be newer than servers.

[aljohn0422]

Got it. Thanks for providing this reference!

[brandond]

Reopening for docs followup