Assistance Required for Non-Responsive EC2 Instance

Question

Hello AWS Support,

I am experiencing an issue with one of my Ubuntu EC2 instances, which fails to start and becomes inaccessible. Here are the details of the problem:

Problem: The EC2 instance does not boot up and remains inaccessible. I mounted its volume on a backup instance as a secondary volume, where I verified that all files and configurations appear correct, and services run normally on the backup instance.

Troubleshooting Performed:

I checked the logs (/var/log/syslog, /var/log/dmesg, and cloud-init-output.log) without finding any clear cause for the failure.
I reviewed configurations in /etc/fstab, ensured critical permissions were set correctly, and disabled some non-essential services.
Despite these checks and adjustments, the instance still does not start.
Instance Volume: I successfully mounted and accessed the original volume on a backup instance, where services are running without issues. This suggests that the data and application configuration are correct.

I am reaching out for your assistance to identify the root cause of the issue or any further diagnostic information that could help explain why the instance is unable to start. Any guidance or recommendations for a quick resolution would be greatly appreciated, as this server is critical to our operations.

Thank you in advance for your assistance.

Best regards,

re:Post Agent · Answer

I understand you're facing a challenging situation with your Ubuntu EC2 instance that's failing to start and becoming inaccessible. Based on the information you've provided, here are some suggestions to help diagnose and potentially resolve the issue:

1. Check EC2 System Log: Review the EC2 system log for any error messages or unusual activity during the boot process. This can often provide valuable insights into why the instance is failing to start.

2. Status Checks: Verify the status checks in the AWS Management Console. If both system and instance status checks are failing, it could indicate a more serious underlying issue.

3. EC2Rescue for Linux: Consider using EC2Rescue for Linux. This tool can help analyze and repair common issues that prevent Linux instances from booting. You can detach the root volume of the problematic instance, attach it to another instance where EC2Rescue is set up, and run the tool for analysis and repair.

4. CPU and Memory Load: If possible, check the CPU and memory load on the instance. High resource utilization could prevent the instance from booting properly.

5. Disk Space: Ensure there's sufficient disk space available. A full disk can cause various issues, including boot failures.

6. Network Configuration: Verify that the network settings are correctly configured for EC2 Instance Connect and SSH access.

7. Driver Compatibility: Ensure all drivers are compatible with your instance type and OS version.

8. File System Issues: Check for any file system corruption that might be preventing the instance from booting.

If these steps don't resolve the issue, you may need to consider more advanced troubleshooting techniques or potentially recreate the instance using the data from your mounted volume. Remember to take regular backups to minimize data loss in such situations.

Given that you've already mounted the volume on a backup instance and verified the data, you're in a good position to recover if needed. However, identifying the root cause is crucial to prevent future occurrences.  
**Sources**  
[EC2 Linux instance unresponsible/unreachable | AWS re:Post](https://repost.aws/questions/QUJNev4-4ZQH6Jw_WT7sOF0w/ec2-linux-instance-unresponsible-unreachable)  
[EC2 instance suddenly stopped working. | AWS re:Post](https://repost.aws/questions/QUOOiofUHlQnCp4R7meq0c9w/ec2-instance-suddenly-stopped-working)  
[Troubleshoot EC2 Windows instance status check failures | AWS re:Post](https://repost.aws/knowledge-center/ec2-windows-status-check-failures)  
[Unable to connect to EC2 Ubuntu instance as the instance check fails | AWS re:Post](https://repost.aws/questions/QUfXUcgAcPSmKnafvyJUe4jQ/unable-to-connect-to-ec2-ubuntu-instance-as-the-instance-check-fails)  
[EC2 Instance Connect doesn't work | AWS re:Post](https://repost.aws/questions/QUdFebYgU7TGC9wyL3V2FZBA/ec2-instance-connect-doesn-t-work)

Assistance Required for Non-Responsive EC2 Instance

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