Google Cloud VM instance restarts unexpectedly

Question

A Google Cloud VM did restart unexpectedly. According to the log:

• BootCounter changed from 2 to 3 (no shutdown notice?)
• Shielded VM integrity trips
  • earlyBootReportEvent and lateBootReportEvent, policyEvaluationPassed: false
• Instance migration happens (should not lead to reboot?)
• Few lines for OS boot shown (OSConfig, GCE Agent, Updating keys, etc)

When connecting with SSH and running htop, the uptime indicates it has been restarted.

VM settings:

• Preemtibility (Off)
• On host maintenance (Migrate)
• Automatic restart (On)

Can someone shed some light on why this VM did restart?

• Did it restart due to maintenance and therefore trip the Shielded VM?
• Did the Shielded VM somehow got tripped and therefore it did restart?

Answer 1

Notice the compute.instances.migrateOnHostMaintenance operation in your Stackdriver logs; according to your On host maintenance (Migrate) setting, what you have experienced here is a live migration :

By default, standard instances are set to live migrate, where Compute Engine automatically migrates your instance away from an infrastructure maintenance event, and your instance remains running during the migration. Your instance might experience a short period of decreased performance, although generally most instances should not notice any difference. This is ideal for instances that require constant uptime, and can tolerate a short period of decreased performance.