SSH is a secure way to communicate with your Linode server. But, often SSH connectivity problems can deny access to your Linode server.

Things become more frustrating when you cannot access the Linode server for last minute changes.

At Bobcares, we help server owners to regain SSH access to Linode servers as part of our Managed Cloud Services.

Today, we’ll see the top reasons for SSH access failure on Linode servers and how we fix them.

What causes SSH connectivity problems in Linode?

From our experience in managing Linode servers, our Support Engineers often see Linode owners reporting problems with SSH access. It becomes critical due to the fact that server becomes inaccessible. Let’s first check the top reasons for SSH failure in Linode servers.

1. Bad SSH configuration

Server owners often tweak SSH service on Linode to make servers secure. This includes disabling features like Password Authentication, not allowing direct root login, etc. After making these changes, it requires a service restart. This revokes all ssh access sessions. And, if proper access is not allowed, server becomes inaccessible.

For example, we often see ssh lock out scenario after disabling Password Authentication without adding proper SSH keys. The same happens when you disable root login without adding proper ssh users.

2. Firewall restrictions

Similarly, firewall restrictions can also block Linode SSH access. When you have SSH listening on a custom port, other than port 22, the firewall should allow this traffic. And, if the custom port is not open in your computer or your Internet Service Provider, there will be ssh failure.

3. Networking errors

Again, Linode can experience SSH problems due to server networking errors too. We predominantly see these errors after server reboot or maintenance. Here, the server fails to bring up the network interface eth0. This further creates problems in entire server, including SSH access.

4. SSH service errors

Again, Linode server will be up, but the SSH service fails to start. Server owners experience SSH problems because of this too.

How we regain SSH access in Linode?

So far, we saw the various reasons that can cause failure of SSH access in Linode server.  Updating your applications become rather impossible without access to the server.

Let’s now see how our Dedicated Support Engineers fix and regain SSH access to the server.

The first step in troubleshooting Linode SSH access is to ensure that server is accessible via ping command.

ping serverIP

On successful connection, there should be 0% packet loss.

--- 172.17.3.43 ping statistics ---
8 packets transmitted, 8 received, 0% packet loss, time 7163ms

When server is accessible, the next step is to check SSH access in Verbose mode using the command :

ssh -vvv <user>@<IP address> -p<port>

Here, we need to provide SSH username, password, server IP address and custom ssh port.

This gives more details on the access problem. If this also fails, our Support Engineers further troubleshoot from the Lish Console accessible from web-based control panel Linode Manager.

Linode name >> Remote Access tab >> Launch Lish Console.

Here, we correct the SSH configuration file at /etc/ssh/sshd_config, and then track the login attempts at /var/log/auth.log.

If there are problems connecting to Linode server even after fixing SSH, we temporarily disable the server firewall. This help us to isolate firewall issues. Also, a telnet connection from the customer’s computer to server SSH port helps to diagnose internet service provide firewall problems too.

Additionally, we often restart SSH service to ensure that the Linode interface properly listens on the SSH port.

[Trouble connecting to Linode servers? We can fix SSH for you.]

Conclusion

SSH access to Linode servers can fail due to bad firewall, wrong SSH configuration or even networking problems. Today, we’ve seen the top reasons for SSH failure and how our Dedicated Engineers fix them and regain access to Linode.