Scenario 1: EC2 Instance Unresponsive or Failing Status Checks

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Mind Map:

Podcast Discussion:

Problem:

• A critical EC2 instance running a web application becomes unreachable.
  
  

• Users report downtime, and the AWS console shows failing system or instance status checks.
  
  

Step-by-Step Troubleshooting:

1. Review Status Checks:
   
   

   • Open the EC2 console and check the instance’s system and instance status checks.
     
     

   • If system status check fails, it likely indicates a hardware or AWS infrastructure issue.
     
     

   • If instance status check fails, it suggests an OS-level problem inside the instance.
     
     

2. Examine System Logs and Console Output:
   
   

   • Access the console output of the instance from the EC2 console.
     
     

   • Look for kernel panics, boot errors, or misconfiguration messages.
     
     

   • Review CloudWatch Logs if the instance is configured to send logs there.
     
     

3. Verify Network Settings:
   
   

   • Check security groups to ensure required ports (e.g., 80, 443, 22) are open for the right sources.
     
     

   • Confirm that Network ACLs are not blocking inbound or outbound traffic.
     
     

   • Verify route table entries and ensure the subnet has a route to an Internet Gateway or NAT if needed.
     
     

4. Assess Recent Changes:
   
   

   • Review if there have been recent changes to IAM roles attached to the instance.
     
     

   • Check if user data scripts have been modified or rerun recently.
     
     

   • Look into OS updates or configuration changes that could affect instance stability.
     
     

5. Recovery Actions:
   
   

   • Attempt to reboot the instance from the EC2 console.
     
     

   • If the reboot does not resolve the issue, perform a stop and start to move the instance to new hardware.
     
     

   • If the instance still fails, detach the root EBS volume and attach it to another instance.
     
     

   • Mount the volume and check system files for issues.
     
     

   • After fixing any identified problems, reattach the volume to the original instance and start it.
     
     

Interview Insight:

• When an EC2 instance becomes unresponsive, I first use AWS status checks to determine if the problem is hardware or OS-related.
  
  

• I investigate console output for boot errors and review network settings.
  
  

• If necessary, I use volume-level access for deep diagnostics and ensure recent changes are evaluated to identify potential root causes.