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Kubelet Restart in AWS EKS: Causes, Logs, Fixes & Node Stability Guide (2025)

Fix Kubelet restarts in AWS EKS with this 2025 guide. Learn root causes, debug logs, CSI issues, and node stability strategies for production-grade clusters.

Author

Ismail Kovvuru
July 21, 2025

Kubelet is the heart of every Kubernetes node. When it restarts unexpectedly, you risk cascading failures—pods getting evicted, CSI volumes unmounting, nodes marked NotReady, and broken workloads.

In 2025, with Kubernetes 1.30+, Bottlerocket OS, cgroup v2, and evolving EKS architecture, understanding and hardening kubelet is non-negotiable for platform stability.

This blog walks through root causes, debugging flow, fixes, and advanced production-grade strategies to ensure node resilience.

Common Symptoms of Kubelet Restarts

  • Node status flips to NotReady

  • Repeated pod evictions

  • Errors like container runtime socket closed, Failed to start ContainerManager, or kubelet panic logs

  • dmesg shows kubelet being killed (OOM)

  • EBS volumes stuck, CSI plugins crash

  • GPU workloads failing after restart

Root Cause Categories

Category

Common Triggers

Resource Pressure

OOM, no CPU left for kubelet

Storage/CSI

Mount stuck, EBS race conditions

OS & Systemd

systemd-oomd, DNS issues, service dependency cycles

Security Agents

Falco, CrowdStrike interfering with kubelet runtime

Kubelet Config Drift

Misconfigured flags, drift across versions

Cloud Failures

IMDSv2 unresponsive, Nitro issues, disk I/O freeze

Debugging Flow

Logs & Runtime Checks

journalctl -u kubelet -r
systemctl status kubelet
dmesg | grep -i kill
free -h && vmstat 1 5
ps aux --sort=-rss | head -n 10
df -h && iostat -xz 1 3

Kubelet Config Validation

cat /etc/kubernetes/kubelet/kubelet-config.json
kubelet --version

 

Kubelet Restart Troubleshooting

Command

Explanation

journalctl -u kubelet -r

View reverse-chronological kubelet logs

`dmesg

grep -i kill`

free -h

View available memory

`ps aux --sort=-rss

head -10`

df -h

Check disk usage (node pressure)

uptime

Confirm node stability duration

curl http://169.254.169.254/latest/meta-data/

Validate EC2 metadata service (IMDSv2)

cat /etc/kubernetes/kubelet/kubelet-config.json

Check kubelet config drift

systemctl status kubelet

Validate systemd health for kubelet

Cloud Observability

  • CloudWatch: Log Insights on /var/log/messages, kubelet logs

  • NodeProblemDetector: Check NodePressure, KernelDeadlock, KubeletOOM

  • Check EC2 metadata: curl http://169.254.169.254/latest/meta-data/

Production-Ready Fixes

Memory & CPU Hardening

kubeReserved:
  cpu: 200m
  memory: 300Mi
systemReserved:
  cpu: 100m
  memory: 200Mi

Disk Pressure

  • Set eviction thresholds properly: 

evictionHard:
  memory.available: "100Mi"
  nodefs.available: "10%"

  • Mount volume cleanup via automation scripts

Node Problem Detector Setup

kubectl apply -f https://raw.githubusercontent.com/kubernetes/node-problem-detector/master/config/default.yaml

Pin Stable Kubelet Version in EKS

eksctl create nodegroup ... --kubelet-extra-args='--node-labels=eks.amazonaws.com/nodegroup=stable --kubelet-version=1.29.3'

CI/CD + Automation

Jenkins/GitHub Actions Steps

  • SSH via SSM to new node

  • Run health-check script (validate kubelet uptime, journal logs)

  • Fail build if node uptime < 10 mins (indicating restart)

Chaos Engineering

  • Inject kubelet crash using AWS FIS or ChaosMesh

  • Validate ASG self-healing, workload migration

Real-World Scenarios

Case 1: EKS Node OOM

  • Kubelet killed silently by kernel

  • Pod disruption in production

  • Fixed via memory reservation + eviction tuning

Case 2: CSI Plugin Crash

  • EBS volume mount failure causes kubelet panic

  • Added health checks to restart CSI pods on failure

Case 3: Security Agent Interference

  • Falco + systemd race

  • Excluded kubelet and containerd dirs in Falco config

Tool

Purpose

NodeProblemDetector

Kubelet/system pressure alerts

eks-node-viewer

Visual node/kubelet status

ChaosMesh

Kubelet crash simulation

AWS Systems Manager

Remote node inspection

CloudWatch Agent

Kubelet metrics/log shipping

kubelet-config-linter

Detect misconfigurations

Kubelet Restart Cheat Sheet

Symptom

Cause

Quick Check

Fix

Frequent restarts

OOM

dmesg, free

Add memory, tune kube-reserved

Node NotReady

Disk full

df -h

Clean logs, expand volume

CNI errors

Kubelet config drift

cat /etc/kubernetes/...

Align configs with AMI

GPU pod crash

Driver not reloaded

nvidia-smi

Hook reload into startup

Security & Compliance Notes

  • Log all kubelet restarts in CloudWatch

  • Audit /etc/kubernetes/kubelet/ using AWS Config

  • Falco rules to detect unauthorized kubelet config changes

  • Alert on frequent kubelet crash patterns

What’s New in 2025

  •  cgroup v2 now default: affects how memory is reported to kubelet

  • Bottlerocket: kubelet managed outside systemd — must debug via admin container

  • IMDSv2 failures common: EKS node bootstrap can fail silently

  • CSI drivers updated — sidecar version mismatch causes restarts

  • Kubelet auto-restarts not logged by systemd in minimal OSes (e.g., Bottlerocket)

Conclusion

In Kubernetes, the kubelet is your node’s pulse. Unstable kubelet = unstable node = broken workloads.

With evolving runtimes, security layers, and cloud-specific behaviors, kubelet stability must be proactively engineered, not reactively debugged.

Use this guide to:

  • Diagnose kubelet restarts confidently

  • Automate detection & healing

  • Stay ahead with 2025-grade strategies

Remember: The best time to fix a kubelet crash was yesterday. The second-best is before it takes down production.

For more topics visit Medium , Dev.to and Dubniumlabs