How can I resolve the instance reachability check failed issue on an Ubuntu AWS instance

Question

I'm facing the 'instance reachability check failed' issue on my Ubuntu AWS instance. It seems like the instance isn't accessible, and I need help figuring out how to resolve this.

Answer 1

1. First, I checked the System Logs to see if there were any boot errors that could point to what went wrong. This is always a good starting point because the logs often show us if there’s an issue with the instance starting up.

2. Then, I performed a reboot of the instance. Sometimes, a quick reboot can solve minor glitches.

3. Next, I made sure that the Security Group settings were correct. Security groups act like a firewall, so it’s important to ensure they’re not blocking anything critical for the instance to work.

4. I also reviewed the network configuration—things like Elastic IP, VPC, and Subnet settings—to make sure the instance was properly connected and had the correct IP.

5. If the disk was full, that could cause boot issues. So, I increased the root volume size just in case that was the problem.

6. For more detailed troubleshooting, I accessed the instance via the EC2 Serial Console. This lets me see what’s going on at a deeper level, including any kernel or boot errors.

Finally, if none of these steps worked, I would consider rebuilding the instance as a last resort. This is typically the last step if the problem can’t be fixed through other means.