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EC2 Troubleshooting

Links: 114 AWS SOA Index

EC2 Launch Troubleshooting

InstanceLimitExceeded

  • If you get this error, it means that you have reached your limit of max number of vCPUs per region.
  • On-Demand instance limits are set on a per-region basis.
  • Example: If you run on-demand (A, C, D, H, I, M, R, T, Z) instance types you’ll have 64 vCPUs (default)
  • Resolution:
    • Either launch the instance in a different region or
    • We can use Service Quotas to request an EC2 quota increase.

[!note] vCPU-based limits ONLY apply to running On-Demand instances and Spot instances.

A SysOps Administrator attempted to launch an Amazon EC2 instance and received the following error: InstanceLimitExceeded Your quota allows for 0 more running instance(s). What action should the Administrator take to resolve this issue and launch the EC2 instances?

Open a case with AWS Support requesting an increase of the EC2 instance limit.

InsufficientInstanceCapacity

  • If you get this error, it means AWS DOES NOT have that enough On-Demand capacity in the particular AZ where the instance is launched.
  • Resolution:
    • Wait for few mins before requesting again.
    • If requesting more than 1 requests, break down the requests. If you need 5 instances, rather than a single request of 5, request one by one.
    • If urgent, submit a request for a different instance type now, which can be resized later.
    • Also, can request the EC2 instance in a different AZ.
Mind the difference between InstanceLimitExceeded (region level) and InsufficientInstanceCapacity (AZ level).

InstanceTerminatesImmediately

  • Goes from pending to terminated.
  • Possible reasons:
    • You've reached your EBS volume limit.
    • An EBS snapshot is corrupt.
    • The root EBS volume is encrypted and you DO NOT have permissions to access the KMS key for decryption.
    • The instance store-backed AMI that you used to launch the instance is missing a required part (an image.part.xx file).
  • To find the exact reason, check out the EC2 console of AWS instances - Description tab, note the reason next to the State transition reason label.
A SysOps Administrator launched an Amazon EC2 instance and noticed it went from the pending state to the terminated state immediately after starting it. What is a possible cause of this issue?

The root EBS volume is encrypted and the Administrator does not have permissions to access the KMS key for decryption.

SSH Troubleshooting

  • Make sure the private key file on your linux machine has 400 permissions, else you will get Unprotected private key file error.
  • Make sure the username for the OS is given correctly when logging via SSH, else you will get Host key not found, Permission denied, Too many authentication failures or Connection closed by instance port 22 error.
  • Possible reasons for Connection timed out to EC2 instance via SSH:
    • SG is not configured correctly
    • NACL is not configured correctly
    • Check the route table for the subnet (routes traffic destined outside VPC to IGW)
    • Instance doesn’t have a public IPv4
    • CPU load of the instance is high

How SSH instance connect works

  • The EC2 instance will have an inbound rule in which we will allow a specific range of IP from AWS that corresponds to the AWS EC2 Instance Connect range.
    • Without this it won't work.
    • We probably never noticed this since we always had an SG which allowed port 22 access from all locations (0.0.0.0/0)
  • SSH instance connect pushes an one time public key.
    • attachments/Pasted image 20230302092410.jpg

Last updated: 2023-03-18