Ошибка can not resolve hostname

SSH stands for secure shell, and it is a security protocol that provides end-to-end encryption of data. SSH could not resolve hostname is an error message that occurs when the host system fails to resolve the IP address of the remote host provided with the ssh command. Ssh protocol is widely used to provide secure remote shell access.

The ssh command is used to connect to a remote host. The ssh command requires a hostname to connect to, which is then inquired from a DNS(Domain Name System) server that sends the IP address of the remote host the user is trying to login to. If, for some reason, if the hostname is not resolved, then the ssh could not resolve the hostname error message is displayed.

Understanding SSH

Secure Shell is an intermediate protocol that is implemented between the application layer and the transport layer of the Internet protocol stack. It works on top of the TCP protocol, ensuring reliable delivery and data integrity. To connect to a remote shell, use the ssh command and provide the username and the hostname of the remote host you are trying to connect. Public key cryptography is used to authenticate the user. The private key is stored in the user’s host, which provides authentication. The ssh could not resolve hostname is one of the common errors faced while using ssh.

SSH hostname resolution and DNS

The hostname provided in the ssh command has to be resolved to an IP address, i.e., the address of the remote host in computer-readable form. The hostname can be provided in the IP address form example, 192.168.43.89, or a name can be used instead of example.com, for example. A DNS server is used to resolve the hostname to an IP address. The string of characters provided as the hostname in the command is sent to the DNS server, which then, in turn, returns the IP address of the host.

If the host is unable to contact the DNS server or the DNS server doesn’t return a valid IP address in return then, ssh could not resolve the hostname error that occurs. The ssh could not resolve hostname can also happen due to the cached DNS data stored in the system. Frequently used Domain name addresses are stored in cache storage in the host system so that the system doesn’t need to enquire the DNS server every time it makes a request. If the cache data is outdated or the host’s IP has been charged, the cached data becomes useless and can cause problems like ssh could not resolve the hostname.

If you are receiving the ssh could not resolve the hostname error, then a few steps can be employed to resolve and avoid this error message. Consider the given steps to fix the ssh could not resolve the hostname error.

Check the hostname

Most of the basic and simple measures to avoid the ssh could not resolve hostname is to check whether the hostname you are using with the ssh command is correct or not. Using the wrong hostname or domain address might result in a Wrong DNS response or no valid response at all. Check your hostname address for typos and syntax errors of the command. If everything is correct but still getting the hostname does not resolve the error, then employ the following measures.

Clearing DNS Cache

Clearing the DNS cache might also help resolve the ssh could not fix the hostname error. After the DNS cached data is deleted, a new fresh DNS inquiry is sent to the DNS server for each request, which would be beneficial if the IP address of the host is changed. Follow the given steps to clear the DNS cache in Windows.

• Press Windows + R.
• Enter cmd in the serach box and hit enter.
• In the shell Enter the command ipconfig /flushdns.
• The DNS cache is not cleared.
• Try running the ssh command again.

For Ubuntu users, Enter the following command in the terminal to clear the DNS cache manually.

Editing the /etc/hosts file

If you are trying to connect to a remote host using ssh for the first time and getting a hostname error not resolved error in return, try editing the ssh hosts file and entering the username and hostname in the file. Employing the given steps to edit the hosts’ file and fix the ssh could not resolve the hostname error.

• Open the terminal emulator.
• Enter sudo nano /etc/hosts.
• Enter your root password.
• Now in the file, enter the IP address and hostname of your remote host.
• Press ctrl + O to save the file.
• Press ctrl + X to exit nano.
• Run the ssh command again.

SSh could not resolve hostname github.com

The ssh could not resolve hostname error can also show up while using the git version management program. The git uses the ssh while cloning a repository or pushing a remote repository. The issue can be fixed with the following steps.

• Try to ping the github.com using the ping github.com command. If the server responds then try to run the git command again after rebooting the system, it might be a normal network issue.
• If the issue persists, follow the steps mentioned above, such as clearing the DNS cache.
• Run the following command to restart the network manager in linux, which might help resolve the issue.

sudo service network-manager restart

SSH could not resolve hostname Gitlab

Gitlab is another popular open-source platform that is widely used in DevOps operations. “ssh: Could not resolve hostname gitlab.example.com: Temporary failure in name resolution” is the error message that is displayed while logging into the GitLab server. As the message itself suggests, this is a temporary failure in the name resolution, and chances would be resolved automatically after some time. But if the problem persists, follow the steps suggested above to make it work. You could also try adding ssh:// before the git URL to resolve the hostname issue.

git clone ssh://[email protected]:username/This_is_a_demo.git

SSH could not resolve hostname Gitbucket.org

Bitbucket is another open platform used to host git repositories online. The same hostname resolution problem can be encountered with gitbucket.org as with github.com. To resolve this issue, use the suggested methods and configure your .git config file. Open the config file in the .git folder for your project’s main directory. Change the remote directory listing as mentioned below (remove the ssh:// in the config file) and rerun the command.

url = ssh://[email protected] 
//before

url = [email protected]
//after

FAQs on SSH Could Not Resolve Hostname

What is TCP?

It stands for Transfer Control Protocol. It is a transport layer protocol that ensures the reliable hosts-to-host delivery of the data packets.

What is the difference between git and GitHub?

Git is a version management program that keeps track of the changes in a project, While GitHub is an online platform where people can share their git repositories.

What is the Linux equivalent of ipconfig?

The Linux equivalent of the ipconfig command is ifconfig.

Conclusion

The ssh could not resolve hostname is a common error that any user can face. It is not that big of an issue. It simply happens when the ssh command fails to resolve the IP address of the provided hostname. In such situations clearing the DNS cache or editing the /etc/host file can help. This article provided you with the necessary measure and solutions to fix this error. In the end, we also mentioned what to do if you are receiving this error while using the git CLI.

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As WooJoo stated, you need to tell it a valid server to connect to. If you wanted to use the form $ ssh root@server you can, but you would need to have server as an entry in /etc/hosts or your dns server (which is not the case or you would not have had an error), or an entry in a file called config located typically at /home/username/.ssh/config.

A sample /etc/hosts entry would look like:

# Sample /etc/hosts file
127.0.0.1    localhost
127.0.1.1    computerhostnamehere

10.0.2.15    server

and a sample /home/username/.ssh/config could be as simple as:

Host server
  HostName 10.0.2.15
  User root

This would get you the basic functionality you are looking for. There are many more options available for placing in the ~/.ssh/config file.

See man ssh for more options

You may get an error message when connecting to a machine that says ssh: Could not resolve hostname server: Name or service unknown. This might happen if you cannot connect wirelessly or don’t have enough signal strength for your device, but it can also occur because of typos in the command line prompt.

In this article, we’ll discuss how to fix it so you can reaccess your machine.

What is SSH?

Secure Shell (SSH) is an intermediate protocol between the application and transport layers of the Internet protocol stack. To create a connection to a remote shell, use the ssh command providing the username and hostname of the remote server.

Authentication uses public key cryptography, storing a private key in the user’s host. The error ssh: Could not resolve hostname is one of the most common errors encountered when using SSH.

How Does SSH Resolution With DNS?

To initiate a secure connection via SSH, a hostname must be resolved to an IP address. This can be done by providing the remote system’s IP address (e.g., 74.6.11.164) or its domain name (e.g., techcolleague.com).

A DNS server is used to translate the hostname into an IP address, and if this process fails, an error that reads “ssh could not resolve the hostname” may occur.

Additionally, systems will often store frequently-used domain names in their cache storage, so they don’t have to query a DNS server every time they attempt a request – but if this data is outdated or incorrect, it can lead to similar errors with SSH resolution.

Solution 1: Ping the Host

If you’re having difficulty connecting to a host via SSH, you should try pinging it using the ping command. If the host does not respond, it may be due to an issue on the server side.

If the host responds, there might be a network issue. Check if you can SSH to other hosts.

Solution 2: Check the Hostname

When trying to SSH to a server, verify your full command. You may be typing a command that the ssh program does not understand.

Here is an example of a command you may have run:

As you can see, the error is about not resolving the hostname myserver.

When you use the ssh program, the command you will use should be the following:

ssh [email protected]
ssh root@74.6.11.164

In the previous example, the user is root and hostname is myserver which is not a valid hostname. The correct example is shown you provide user as root and hostname as 74.6.11.164.

Solution 3: Fix the Hosts File

Hostname problems can also arise due to damage to the hosts file (i.e., /etc/hosts). Sometimes, ssh can give the same warnings for such errors as other issues. To edit the hosts file, root access is required.

Type the following command to open the file for editing:

sudo nano /etc/hosts

If you’re familiar with the vi program, you can also edit the file using vi by typing:

sudo vi /etc/hosts

The sudo prompt will ask for your password.

Make sure you have read and write access to the hosts file and look at the top of the file. You will need the following two lines for it to work correctly:

127.0.0.1 localhost
127.0.1.1 myhostname

Replace “myhostname” with your machine’s actual hostname. If you are working with an IPv6 network, you may also need these lines:

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

In most cases, correctly setting the first two lines is sufficient for networks that use only IPv4 technology. However, modern Internet connectivity is quickly moving towards the IPv6 standard, so you may need to set these additional lines in the future.

Your Linux distribution should have configured these settings for you, but errors can occur due to an errant package or user mistakes that corrupt the hosts file and direct connections to the wrong location.

Solution 4: Add an Entry in /etc/hosts

You may have a scenario where you want to specify myserver as your hostname because you don’t want to type the IP address 74.6.11.164. In this case, you need to add an entry in /etc/hosts.

To make this change, open the /etc/hosts file and add myserver line to the end of the file such as the following example:

Once this entry has been saved in /etc/hosts, you can ssh to the server by typing:

ssh [email protected]

You should not be able to connect to your specified server.

Solution 5: Check the Hosts Directive

If the previous solution didn’t fix your issue, it may be the ordering of the hosts directive in your /etc/nsswitch.conf file.

Take a look at your /etc/nsswitch.conf. It should have this line:

hosts: files dns

With the above line, your Linux system will look at files first, which is /etc/hosts to resolve DNS. If it finds nothing there, it will query DNS in /etc/resolv.conf.

If your /etc/resolv.conf shows a different entry than the above, you may consider updating it and then connect to your server again.

Frequently Asked Questions

Conclusion

This article explains the steps to resolve the error “ssh: Could not resolve hostname.” The error can be caused due to various reasons like incorrect hostname or command line prompt, missing entry in /etc/hosts, or incorrect ordering of the hosts directive in /etc/nsswitch.conf.

This article provides solutions to fix the issue. By following these steps, you can successfully connect to your machine.

If you’ve been getting the error message “ssh: Could not resolve hostname Name or service not known,” don’t worry, you’re not alone.

This is a common problem that can be fixed in a few simple steps. In this blog post, we will discuss three ways to fix the ssh error message.

We will also provide instructions on how to troubleshoot this problem if it persists.

How to fix ssh: Could not resolve hostname Name or service not known

• Check your ssh command syntax and make sure you type your command correctly.
• Check your hostname exists in DNS and make sure the hostname can be resolved to the correct IP address.
• Update your /etc/hosts file with an entry mapping the IP address of the server if necessary

Check your ssh command syntax

ssh is a secure shell client command used to connect to remote servers. The most basic syntax for the ssh command is:

ssh [options] user@server_hostname

or

ssh [options] user@ip_address

The user name is the name of the user you are logging in as, and the server name is the hostname or IP address of the remote server.

For example,

if the server hostname is “example.com” and your user name on the server is “admin”, you would enter:

ssh admin@example.com

If you use the following command, you will get an error.

ssh admin@server example.com

ssh: Could not resolve hostname server: Name or service not known

ssh command also supports different options. These options allow you to set up the connection in different ways.

For example, if you’re trying to establish an SSH connection from a Windows machine, then you could use the -p option to specify the port number for the server.

For example:

ssh -p 33 admin@example.com

If you need to use a private key in the ssh command, then use the -i option to specify the path to your private key.

For example:

ssh -i /path/to/private_key admin@example.com

You can also mix these options like StrictHostKeyChecking together like the following example. Make sure you use the correct ssh command.

ssh -i bastion_dev.pem -o StrictHostKeyChecking=no -o ServerAliveInterval=30 ubuntu@prod-us-west-2.elb.amazonaws.com

Check your hostname and DNS record

If your syntax is correct, we need to check to make sure that the DNS record for your hostname is set up correctly, and if necessary try using the IP address of the server instead of its hostname.

We can use some commands like ping, dig, or nslookup to check the hostname and make sure that your hostname can be resolved by the DNS server.

For example, to check the hostname with the ping command:

ping example.com

If we get a response from this command, it means the DNS server is able to resolve the hostname, and your problem may be related to other factors.

We can also use nslookup or dig command to get more detailed information.

For example:

nslookup example.com

or

dig example.com

If these commands return errors related to the DNS server, then you may need to contact your ISP or hosting provider to help solve the problem.

Update your /etc/hosts file

If the hostname still can’t be resolved, you can try adding an entry in your local machine’s /etc/hosts file mapping the IP address of the server to its hostname.

For example, if the IP address of the server is 192.168.1.100, you would add the following line to your /etc/hosts file:

192.168 .1 .100 example.com

Save the file and try connecting again with ssh command. If it works then you know that the problem is related to your DNS server.

If you are still having trouble, check any firewalls or proxy servers that may be blocking access to the server and make sure they are configured correctly. If all else fails, contact the server’s administrator for assistance.