temporary failure in name resolution

Sometimes when you try to ping a website, update a system or perform any task that requires an active internet connection, you may get the error message ‘temporary failure in name resolution’ on your terminal.

salmanrajz@ubuntu:~$ ping google.com
ping: salmanrajz.com: Temporary failure in name resolution

This is usually a name resolution error and shows that your DNS server cannot resolve the domain names into their respective IP addresses. This can present a grave challenge as you will not be able to update, upgrade, or even install any software packages on your Linux system.

In this article, we will look at some of the causes of the ‘temporary failure in name resolution‘ error and solutions to this issue.

1. Missing or Wrongly Configured resolv.conf File

The /etc/resolv.conf file is the resolver configuration file in Linux systems. It contains the DNS entries that help your Linux system resolve domain names into IP addresses.

If this file is not present or is there but you are still having the name resolution error, create one and append the Google public DNS server as shown

nameserver 8.8.8.8

Save the changes and restart the systemd-resolved service as shown.

$ sudo systemctl restart systemd-resolved.service

It’s also prudent to check the status of the resolver and ensure that it is active and running as expected:

$ sudo systemctl status systemd-resolved.service

Then try pinging any website and the issue should be sorted out.

2. Firewall Restrictions

If the first solution did not work for you, firewall restrictions could be preventing you from successfully performing DNS queries. Check your firewall and confirm if port 53 (used for DNS – Domain Name Resolution ) and port 43 (used for whois lookup) are open. If the ports are blocked, open them as follows:

For UFW firewall (Ubuntu / Debian and Mint)

To open ports 53 & 43 on the UFW firewall run the commands below:

$ sudo ufw allow 53/tcp
$ sudo ufw allow 43/tcp
$ sudo ufw reload

For firewalld (RHEL / CentOS / Fedora)

For Redhat based systems such as CentOS, invoke the commands below:

$ sudo firewall-cmd --add-port=53/tcp --permanent
$ sudo firewall-cmd --add-port=43/tcp --permanent
$ sudo firewall-cmd --reload

It’s our hope that you now have an idea about the 'temporary failure in name resolution' error and how you can go about fixing it in a few simple steps. As always, your feedback is much appreciated.

 

 

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