Ubuntu 24.04 LTS – kubeadm init fails preflight due to swap 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

kubeadm preflight fails and cluster bootstrap cannot continue.

Environment & Reproduction

Seen on fresh Ubuntu hosts with default swap file active.

swapon --show
free -h
sudo kubeadm init

Root Cause Analysis

Kubernetes requires swap off for stable memory scheduling on many deployments.

Quick Triage

Verify swap state and kubelet logs.

swapon --show
sudo systemctl status kubelet
sudo journalctl -u kubelet -n 120 --no-pager

Step-by-Step Diagnosis

Identify swap entries in fstab and cloud-init files.

grep -n 'swap' /etc/fstab
ls -l /swap.img 2>/dev/null || true
cat /proc/swaps

Solution – Primary Fix

Disable active swap and remove persistent mount entry.

sudo swapoff -a
sudo sed -i.bak '/sswaps/s/^/#/' /etc/fstab
swapon --show

Solution – Alternative Approaches

Use kubelet config to tolerate swap only for specific lab scenarios.

sudo sed -i 's/^KUBELET_EXTRA_ARGS=.*/KUBELET_EXTRA_ARGS=--fail-swap-on=false/' /etc/default/kubelet
sudo systemctl restart kubelet

Verification & Acceptance Criteria

No swap devices active and kubeadm preflight passes.

swapon --show
sudo kubeadm init --dry-run
sudo systemctl is-active kubelet

Rollback Plan

Re-enable swap if host role changes away from Kubernetes.

sudo sed -i '/swap/s/^#//' /etc/fstab
sudo swapon -a
swapon --show

Prevention & Hardening

Bake swap-off policy into node provisioning templates.

grep -n swap /etc/fstab
cloud-init status --long

Related Errors & Cross-Refs

Can co-occur with cgroup driver mismatch between kubelet and container runtime.

Related tutorial: View the step-by-step tutorial for Ubuntu 24.04 LTS.

View all Ubuntu 24.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Kubernetes on Ubuntu installation and kubeadm preflight guidance.