Incident Library
Applied filters ComponentNode operating system imageSymptomService outageFactorLimited debug accessClear allEvery case under the filters, with no sentence; newest first.
Suggested filters Search, and the values found in your words appear here.

Graph

  • Root cause
  • Component
  • Symptom
  • Contributing factor
  • Case

Cases1 case

1 to 1 of 1

  1. IL-0153 DOKS worker nodes went NotReady at 06:00 UTC on three days because a systemd timer in the Debian image ran apt upgrade and killed it mid kernel upgrade, breaking node networking
    DigitalOcean2023
    Symptoms

    Customers of DigitalOcean Managed Kubernetes (DOKS) saw worker nodes go NotReady between 06:00 and 07:00 UTC and stay unavailable, taking down the services on them, until the nodes were replaced or rebooted; some nodes needed several replacements or reboots. The first sporadic reports on October 8 said replacing the node fixed it. The same thing happened again around 06:00 UTC on October 9, more widely and across many regions, and again on October 10. Only clusters on versions 1.27.6-do.0 and 1.28.2-do.0 were affected.

    Node NotReadyService outage
    Trigger

    A systemd timer in the DigitalOcean Debian image started apt upgrade daily at 06:00 UTC, with a random delay of up to 60 minutes.

    Root cause
    Configuration change
    Component
    Node operating system imageLinux kernelkubelet
    Contributing factor
    Unreviewed defaultsLimited debug accessChange with a delayed effect
    Detection

    Sporadic customer reports of failed worker nodes arrived at 07:43 UTC on October 8; internal incident response started at 07:10 UTC on October 9 after broader impact across regions.

    Remediation
    • Advised customers to replace or reboot affected worker nodes
    • Arranged SSH and console access to worker nodes while they were healthy, and live-debugged an affected node on October 10
    • Released a DaemonSet to all affected clusters that disables the apt upgrade systemd timer on every worker node
    • Released new node images without the auto-update process
    Action items
    • Disable the timer during node provisioning, then remove the DaemonSet from all clusters
    • Add a check to the internal conformance test suite for new cluster versions that the auto-upgrade process and other unwanted timers stay disabled
    • Support logging into worker nodes even when normal access paths are broken
    Lessons

    An operating system auto-update timer left enabled in a node image can change the kernel and systemd underneath Kubernetes, and a timeout that kills the upgrade half-way can leave a node without networking. Failures that start at the same time every day point to a scheduled job on the nodes, and systemd timers belong on that list next to cron jobs. When the failure takes out a node's network, an investigation that depends on logging into the node stalls; access paths that work while the node is broken shorten diagnosis.

    View case
Check your cluster for this

This case involves kubelet and Linux kernel. kubegap audits a Kubernetes cluster for gaps like these, read-only, from Claude Code or Codex; its checks cite public reports like the ones in this library.

Open kubegap

By root cause1

Configuration change1 case

Component
kubeletLinux kernelNode operating system image
Contributing factor
Unreviewed defaultsChange with a delayed effectLimited debug access
Organisation
DigitalOcean
  1. IL-0153 DOKS worker nodes went NotReady at 06:00 UTC on three days because a systemd timer in the Debian image ran apt upgrade and killed it mid kernel upgrade, breaking node networking
    DigitalOcean2023