DNS, or a Domain Name System, is responsible for resolving website names into their respective IP addresses. There are multiple DNS servers and you can pick and choose the one you want to use. So, if you’re having trouble connecting to a website, or if you just want a DNS change to be seen by your Ubuntu machine, you should try to flush the DNS cache. You can also clear DNS cache in Ubuntu if you made changes to the hosts file, and you want it to be “seen” by your system without having to reboot it. Well, if you’re in any of these situations, and you want to clear DNS cache, here is how to flush DNS cache in Linux.
Before we get to our tutorial, let’s see first if DNS caching is enabled on your machine or not.
All Linux distros do not behave the same way, when it comes to things like caching DNS. For example, Ubuntu, by default, doesn’t cache DNS. Before we try to clear DNS cache on a Linux machine, let’s check if caching is even enabled. To do this on an Ubuntu system, you can follow the steps below:
If your Linux system is caching DNS entries, then you can try to flush the DNS cache in order to get rid of any DNS related problems. To clear DNS cache in Ubuntu, you can follow the steps below:
- Launch Terminal (ctrl + alt + T), and type “sudo /etc/init.d/dns-clean restart“.
Flush DNS Cache in DNS Services on Linux
Like I said, Ubuntu doesn’t cache DNS entries by default, however, if you have manually installed a DNS service such as nscd, you can clear its cache. Methods to clear cache for some common DNS services are given below:
sudo /etc/init.d/nscd restart
sudo /etc/init.d/dnsmasq restart
If you’re using BIND, you can clear DNS cache by using one of the following commands:
sudo rndc restart
To clear DNS cache for WAN, use “sudo rndc flush wan“
We’ve been talking about flushing the DNS cache in Ubuntu, however, there may be cases where you just want to make a change to the DNS settings in Ubuntu. If you want to change the DNS settings in Ubuntu, you can do that using the GUI, or via the Terminal.
Using the GUI to change DNS settings is easier than using the Terminal. However, if you use multiple connections, you will have to change the DNS setting for each one of them. To change DNS settings using the GUI, just follow the steps below:
- Click on the arrow next to the name of the network you’re connected to.
If you don’t want to use the GUI, and prefer changing DNS settings using the Terminal, you can do this by adding the nameservers to the dnsmasq config file. However, dnsmasq does not come installed by default in Ubuntu systems (dnsmasq-base, does). So, first you’ll have to install dnsmasq by launching a Terminal, and using “sudo apt-get install dnsmasq“.
SEE ALSO: How to Boot a Live Linux USB on Mac (Guide)
