Ubuntu Linux free tier getting into "Instance reachability check failed" at least once in 24hrs.

Hello Sankar

Thank you for your question, I would start by checking the console logs and instance screenshot when the instance starts failing reachability checks,

To get console output

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/
2. In the left navigation pane, choose Instances, and select the instance.
3. Choose Actions, Monitor and troubleshoot, Get console logs.

To get screenshot

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/
2. In the left navigation pane, choose Instances, and select the instance.
3. Choose Actions, Monitor and troubleshoot, Get instance screenshot.

Instance status check failures may occur for the following reasons and you can review the following documentation to troubleshoot unreachable instances.

Since your issue occurs "atleast once every 24hours" this could be attributed to resource over utilization, this knowledge center article will help with narrowing down your issue. Generally Linux doesn't allow you the option to log resource utilization as these metrics are analyzed in real time, You can use tools like ATOP or SAR to log utilization and review them later once accessibility to your instance has been restored. Sharing guide to configure ATOP and SAR on this link and how to use these tools for review can be viewed here

Feel free to update the thread with any questions you might have, thanks