Why did my EC2 instance reboot or restart itself?

Last updated: 2021-11-12

Why did my Amazon Elastic Compute Cloud (Amazon EC2) instance reboot or restart unexpectedly?

Short description

Although unexpected reboots or restarts are rare, there are several reasons these might occur. The following are the most common reasons:

  • The instance failed one or both of its status checks.
  • The underlying hardware hosting your instance was faulty and Amazon EC2 restarted the instance to move it to new, healthy hardware.
  • Scheduled maintenance occurred on your instance that required a reboot.
  • A user or application inside your server rebooted the instance.
  • A kernel bug. If you encounter a kernel bug, be sure that your kernel is fully updated.
    To update the kernel, run one of the following commands or similar, depending on your Linux Operating system and version:
    • sudo yum update kernel
    • sudo zypper up kernel-default
    • sudo apt upgrade linux-image-aws


There are several actions that you can take to determine why your instance rebooted:

View status checks

View system logs

If the instance didn't fail a status check, then the instance might have rebooted due to operating system-level issues. Review the system logs to determine what error occurred. The system logs are located at /var/log/messages or /var/log/syslog depending on your OS distribution.

View reboot history

Use the following commands to determine if a user or an application inside the server initiated the reboot:

# grep reboot /home/*/.bash_history
# grep reboot /root/.bash_history
# history | grep -i reboot
# history | grep -i init
# last reboot

View AWS CloudTrail Events history

Instance reboots initiated from the Amazon EC2 console or through the AWS CLI appear in CloudTrail Events history. To view these events:

  1. Open the AWS CloudTrail console.
  2. Choose Event history.
  3. Select Event name from the filter dropdown list, and then enter RebootInstances.

Note: You can create an Amazon CloudWatch alarm that automatically recovers instances experiencing underlying hardware issues resulting in reboot. For information on how to set up the CloudWatch alarm, see Recover your instance.

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