Hey there, let's work through this SSH connection issue step by step—you've already checked the basics, so let's cover the common gotchas that often trip people up:

• Fix private key permissions first
  macOS enforces strict permissions for SSH private keys—if yours are too open, SSH will reject them outright. Run this command to set the correct permissions:

  chmod 600 ~/.ssh/mykey.pem
  

  This locks down access so only your user account can read the key, which is required for SSH to use it.

• Don't forget the AMI-specific username
  Your current SSH command is missing the username, which varies depending on the EC2 AMI you used:

  • Amazon Linux 2/Amazon Linux 2023: Use ec2-user
  • Ubuntu: Use ubuntu
  • CentOS/RHEL: Use centos or ec2-user (depends on version)
  • Debian: Use admin or debian

  Update your command to include the username, like this example for Amazon Linux:

  ssh -v -i ~/.ssh/mykey.pem ec2-user@ec2-***.us-east-2.compute.amazonaws.com
  

• Double-check your security group setup
  Even if you added an SSH rule, there are two easy mistakes here:

  • Make sure the source IP is your public IP address (not your local network IP). If you're on a home network with dynamic IP, your address might have changed since you added the rule.
  • Verify the security group with the SSH rule is actually attached to your EC2 instance—sometimes we accidentally modify the wrong security group in the AWS console.

• Verify network accessibility

  • Confirm your EC2 instance has a public IP or elastic IP attached (you can check this in the EC2 console under "Instance details").
  • If your instance is in a VPC, ensure the subnet's route table includes a route to an internet gateway—without this, the instance can't reach the public internet to accept your SSH connection.

• Use the verbose log to pinpoint the issue
  You're already using the -v flag, which generates detailed logs. Look for key error messages:

  • "Connection timed out": This usually points to a security group or network ACL issue (make sure network ACLs allow inbound port 22 and outbound all traffic).
  • "Permission denied (publickey)": This means either your username is wrong, the private key doesn't match the public key attached to the instance, or the key permissions are still incorrect.

内容的提问来源于stack exchange，提问作者Tim Biegeleisen