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SSH Connection Troubleshooter

This guide is specifically for troubleshoot an existing node that you are unable to create a remote connection with, that previously worked.

◽ Common Troubleshooting

  1. Verify the username for the VPS you are connecting to is correct.
  2. Verify your SSH key pair file names.
  3. Verify the permissions on your SSH key pair are correct (read only).
  4. Verify that the public key for your VPS is present on the server.
  5. Verify that you have your private key on your local system and that you have the correct name for this file.

◽ Local IP address change

One of the leading causes of connection problems occurs when the system used to establish the remote connection to your node—whether it’s a Macintosh, Windows, or Linux machine—has undergone changes.

Many internet service providers (ISPs) lease IP addresses to their customers for extended but temporary periods. In addition, due to factors like inactivity, lease expiration, equipment updates, or network reconfiguration, your local IP address may change.

ISPs implement this process to “recycle” IP addresses from a limited pool, ensuring availability for all customers, especially when the number of customers exceeds the available IP addresses assigned to that provider.

◽ Symptoms

  • Your PuTTy session may just sit with a blank screen for a period of time and then alert you with a connection timeout error.

  • Your terminal session may just sit unresponsive for a period of time and then alert you with a connection timeout error.

Example

  • A Macintosh MackBook Pro is sitting at the office of a Node Operator and attempts to connect to their node to do normal checkups during normal morning tasks. The last time they connected to their node was "yesterday".
  • The node's IP address is 13.13.13.13.
  • The node's SSH connection port is 22 (default).
  • The private key used to connect with the node is called my_identity_file
user@my-MacBook-Pro ~ % ssh -i .ssh/my_identity_file nodeadmin@13.13.13.13
ssh: connect to host 13.13.13.13 port 22: Operation timed out
user@my-MacBook-Pro ~ %

◽ Step To Fix

  1. Open a web browser and navigate to www.whatismyip.com.
  2. Record the My Public IPv4: for your notes.
  3. Connect to your VPS's web management console.
  4. Update your SSH rule in your firewall settings.
  5. Attempt to connect again

◽ SSH Key issue

◽ Local

This is an unlikely potential that your SSH private key located on your local system has become corrupted or its location changed. Make sure you are able to find your private key, the name is correct, and the location path is valid.

You can also attempt to restore your private keys from your backup.

IMPORTANT

If you do not have a backup, once this connection issue is fixed, create a backup.

◽ Remote

If you have access to your VPS through another method, such as the web console provided by your cloud provider, validate that the user you are attempting to connect as has the public SSH key correctly placed in the .ssh directory of the remote system.

For our examples, our username is nodeadmin.

  1. Access your VPS, and refer to SSH Explanation, Mac SSH Guide, and Windows SSH Guide for detailed understanding.
  2. navigate to your .ssh directory
cd ~/.ssh
  1. Do a directory listing of that directory (letter l not number 1).
ls -l
  1. If you do not see your SSH key, you may need to figure out a way to upload your SSH public key back to the server. You may also look in the root, admin, or ubuntu user's directory for the SSH public key.
ls -l /root/.ssh/
ls -l /home/ubuntu/.ssh
ls -l /home/admin/.ssh

If you find your key with a _backup attached to the name of the file, issue the following command and check again:

sudo nodectl enable_root_ssh

Copy the SSH key over to your nodeadmin directory.

sudo cp /root/.ssh/mypublickey.pub /home/nodeadmin/.ssh/mypublickey.pub

Change the ownership to nodeadmin

sudo chown nodeadmin:nodeadmin /home/nodeadmin/.ssh/mypublickey.pub

Once you have regained access to your nodeadmin account, it is a good idea to disable the root access again to help mitigate nefarious access attempts against your root user. 

sudo nodectl disable_root_ssh

◽ Cloud Service Outages

Cloud Provider Outage

Check with your cloud provider by attempting to access the main web console. Typically, if you can access the console, there will be an alert notifying you of potential outages in various regions where your cloud provider operates.

If you are unable to access the web console, this is a sign that the provider is having issues. Do a search engine inquiry to see if any outage reports are available.

VPS Outage

From your cloud provider's web console, check your Instances page to ensure your VPS is running and is not reporting errors.

◽ Internet Down

This may be an obvious reason for why you are unable to access your node; however, if you have no internet connection, verify your access and try again later.

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