If you’re new to logging into secure shell (SSH) servers and navigating SSH certificates, the error message “SSH Could Not Resolve Hostname: Name or Service Not Known” could be something you’ve seen or are currently experiencing.
Fortunately, once you get to know the ins and outs of SSH, this shouldn’t be a problem for you going forward. In this guide, we’re going to walk you through what causes this error, troubleshooting steps, and what elements you might be misunderstanding about your SSH connection commands or host configurations that are causing this error to prevent you from logging in to your desired server.
SSH is an excellent way to securely log in to web servers and other endpoints on the web, but it does require you to have an active SSH connection running on that server and know the login username or password required to access it. If you are using passwordless login through SSH certificates, then you’ll also learn why this error message is most likely caused by the syntax of your ssh login command.
If you’re ready to dive into this error message, troubleshoot it, and understand how you can avoid encountering it again in the future, read on through this guide, and we’ll walk you through the entire step-by-step error resolution process.
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Solutions & Troubleshooting: SSH Could Not Resolve Hostname
When running into an error message during your SSH connection process that states, “SSH Could Not Resolve Hostname: Name or Service Not Known,” there are certain items that you should look at first when determining the solution, including whether your SSH commands are correct and whether or not your SSH server is configured correctly, with the hostnames you’re connecting to included in your configuration.
In the following few sections, we’re going to walk you through the troubleshooting process and explore the most common causes of this error message when trying to configure your secure shell (SSH) connections. Let’s dive into the troubleshooting and resolution process.
Why does this error occur?
Running into an error message that tells you, “SSH Could Not Resolve Hostname: Name or Service Not Known,” isn’t a great experience; fortunately, this error message does have distinct troubleshooting and resolution steps that you can follow to get it figured out as quickly as possible.
The short answer for why this error occurs is this:
The most likely causes for the “SSH Could Not Resolve Hostname: Name or Service Not Known” error is an improperly configured web server host or an SSH command that wasn’t correctly sent to the destination server. If you’re running into this error message, these are the most likely culprits that you should always investigate first.
SSH commands should always be written as follows:
“ssh username <at> domain or IP address,” with the IP address being either your hostname (could be a domain) or in an IP address format such as what you see in this example.
Double-check your SSH connection, and ensure that the hostname you are connecting to is a valid IP address or domain name. If your hostname isn’t valid, then this is the cause of this error message. You can ping the hostname to see if you get a response back and double-check your server settings to ensure that the hostname is configured to receive secure shell (SSH) connections. SSH connections will be accepted on port number 22.
If the hostname you are trying to connect to via. SSH is active and resolves, whether it is an IP address or domain name; the second item you should check is whether your SSH command is correct.
If you are trying to implement SSH connections into a configuration file or build an SSH connection, ensure that your hostnames resolve correctly, whether this is a direct configuration change or a modification you need to make to your server’s /etc/ hosts file to redirect IP addresses to local hostnames.
How to properly troubleshoot & resolve this error
Properly troubleshooting and resolving any “SSH Could Not Resolve Hostname: Name or Service Not Known” error involves first ensuring that the hostname or IP address you’re attempting to connect to through SSH actually resolves and is active.
If you are using a custom, unique hostname and didn’t modify your server’s /etc/ hosts file to point to the right destination, it may not resolve. Similarly, if you are attempting to connect to a domain or IP where your web server isn’t configured to receive SSH connections, you’ll also run into this error.
Is this a typical SSH error with similar solutions every time?
Yes, the error message “SSH Could Not Resolve Hostname: Name or Service Not Known” is a typical error with very similar solutions every time that it comes up. Your first instinct when seeing this error should be to double-check your SSH hostnames, how they are configured, and whether or not your SSH commands are in the right format and pointing to the correct server destination.
In this troubleshooting and resolution guide, we discussed how you could fix the “SSH Could Not Resolve Hostname: Name or Service Not Known” error when receiving it during your SSH connection commands or in your SSH connection building process, whether in a configuration file or custom script.
You should now know that the primary resolution for this error message is to double-check your hostname, ensure it can accept connections and that your domain or IP address is actually one that resolves. Your secondary course of action should be to ensure that custom hostnames resolve properly if being developed locally or run on a local web host, a process that can be done by re-configuring your /etc/ hosts file, for example.
This is a very common error that occurs during the SSH connection process, and by knowing how to troubleshoot your hostnames and ensure you’re connecting to the right destination, you’ll be well on your way to never getting stuck with this particular error again.
Frequently Asked Questions