AWS Certified SysOps Administrator – Associate (legacy) — Question 311

A user is trying to connect to a running EC2 instance using SSH. However, the user gets a Host key not found error. Which of the below mentioned options is a possible reason for rejection?

Answer options

• A. The user has provided the wrong user name for the OS login
• B. The instance CPU is heavily loaded
• C. The security group is not configured properly
• D. The access key to connect to the instance is wrong

Correct answer: A

Explanation

Providing an incorrect OS username during an SSH attempt to an EC2 instance typically results in authentication failure errors. Incorrect security group configurations would cause a connection timeout rather than an authentication rejection, while AWS access keys are used for API/CLI access rather than direct SSH OS login.