NACI Plug-in error while connecting to my ec2 instance via SSH client installed as chrome extensions


I created my ec2 instance attaching a security group which allows inbound HTTP traffic from anywhere. However, when I'm trying to connect to ec2 instance using SSH Client , I get an error "NaCI Plug-in exited with status code Process called exit(255)". Steps Taken to resolve issue :

  1. Checked whether the security group attached to the instance allows HTTP traffic or not ?
  2. Added -o TCPKeepAlive=yes as SSH arguments in connection box. The issue is not resolved yet?

May I know what could be the root cause ?

Thanks Brahmani

asked 21 days ago37 views
1 Answer

Hello Brahmani, The error "NaCI Plug-in exited with status code Process called exit(255)" suggests that there may be an issue with the SSH connection to your EC2 instance. Here are several potential root causes and steps you can take to troubleshoot the problem:

  1. Security Group Configuration:

    • Ensure that the security group associated with your EC2 instance allows inbound SSH traffic. This typically means allowing TCP traffic on port 22 from your IP address or from everywhere (, though the latter is less secure.
  2. SSH Key Pair:

    • Verify that you are using the correct private key file for the SSH connection.
    • Ensure the private key file permissions are secure. For example, on a Unix system, your key should only be readable by you: chmod 400 your-key.pem.
  3. Network ACLs:

    • Check the network ACLs associated with your VPC and ensure they allow inbound and outbound traffic for SSH (TCP port 22).
  4. EC2 Instance State:

    • Confirm that the EC2 instance is running and not stopped or terminated.
    • Check the instance's system logs through the AWS Management Console for any errors that may indicate what's going wrong at the OS level.
  5. Firewall Settings:

    • If you are behind a corporate firewall or using a personal firewall on your local machine, ensure that outbound SSH traffic is allowed.
  6. SSH Service on the EC2 Instance:

    • Verify that the SSH service is running on the EC2 instance. This can be checked using the EC2 Instance Connect feature or the AWS Systems Manager Session Manager if the instance is properly configured for it.
  7. EC2 Instance Reachability:

    • Use the EC2 Reachability Test to ensure that the instance is reachable over the internet.
  8. SSH Client and Browser Plugin:

    • If you are using a browser-based SSH client or a plugin like NaCl, try using a standalone SSH client like OpenSSH or PuTTY to eliminate any plugin-related issues.
  9. Instance Type and Configuration:

    • Some instance types may require additional network configurations. Make sure your instance type doesn't have special networking requirements.
  10. VPC Configuration:

    • Ensure that the VPC's internet gateway, route tables, and subnet configurations are correct and allow traffic to and from your instance.
  11. Public IP or Elastic IP:

    • Check that your instance has a public IP or Elastic IP associated with it and that you are using the correct IP address for the SSH connection.
  12. SSH Client Configuration:

    • Make sure that the SSH client configuration is correct, including the username (for Amazon Linux, it's usually 'ec2-user', for Ubuntu, it's 'ubuntu', and for RHEL, it's 'root' or 'ec2-user').
  13. EC2 Instance Limits:

    • Ensure you haven't reached a limit on the number of EC2 instances you can run, which could affect new instance launches.
Drew D
answered 21 days ago

You are not logged in. Log in to post an answer.

A good answer clearly answers the question and provides constructive feedback and encourages professional growth in the question asker.

Guidelines for Answering Questions