Ubuntu 26.04 LTS – kubelet fails when swap remains enabled – Fix & Prevention

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Kubelet repeatedly fails, preventing node registration and pod scheduling.

Environment & Reproduction

Common after reboot where swap is re-enabled from fstab.

systemctl status kubelet
swapon --show
cat /etc/fstab

Root Cause Analysis

Kubelet policy rejects active swap unless explicitly configured, causing service startup failure.

Quick Triage

Confirm swap state and kubelet error messages.

journalctl -u kubelet -n 120 --no-pager
free -h
systemctl is-active containerd

Step-by-Step Diagnosis

Inspect kubelet config and boot persistence of swap devices.

grep -RIn 'failSwapOn' /var/lib/kubelet /etc/systemd/system/kubelet.service.d 2>/dev/null
lsblk
swapon --summary

Solution – Primary Fix

Disable active swap and remove auto-enable entries from fstab.

sudo swapoff -a
sudo sed -i '/sswaps/s/^/#/' /etc/fstab
sudo systemctl daemon-reload
sudo systemctl restart kubelet

Solution – Alternative Approaches

If swap is required for local policy, explicitly tune kubelet settings for compatible behavior.

sudo sed -i 's/failSwapOn: true/failSwapOn: false/' /var/lib/kubelet/config.yaml
sudo systemctl restart kubelet

Verification & Acceptance Criteria

Swap remains off after reboot and kubelet stays healthy.

swapon --show
systemctl is-active kubelet
journalctl -u kubelet -n 40 --no-pager

Rollback Plan

Restore swap fstab entries if non-cluster workloads require them.

sudo cp /etc/fstab.bak /etc/fstab 2>/dev/null || true
sudo swapon -a

Prevention & Hardening

Apply node bootstrap checks to enforce swap policy before kubelet start.

swapon --show
grep -n swap /etc/fstab
systemctl status kubelet --no-pager

Related Errors & Cross-Refs

May coincide with cgroup driver mismatch and container runtime startup problems.

Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.

View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu kubeadm and kubelet setup guidance for swap and node prerequisites.