Linux interfaces dns nameservers

How do I configure my static DNS in interfaces?

I am not sure if my interfaces refreshed. How do I properly configure my network with my static DNS addresses?

Reboot your computer. Do not run /etc/init.d/networking restart. The error is caused by the default route already existing. This setup looks correct to me.

As Matt H says, /etc/network/interfaces is picky about stuff already existing. You can have a perfect setup, but already have something there, and it will complain. If it is the default route it is complaining about, you can remove it by running ip route del default to get the computer into a state where you can hand over the management of this stuff to /etc/network/interfaces

13 Answers 13

As the questioner gives the contents of his /etc/network/interfaces I infer that he is using ifup to configure interfaces. But since he may actually be using NetworkManager, I will discuss that as well.

If you are using ifup then DNS settings go in /etc/network/interfaces . For each interface you add dns-* options appropriate for the nameserver(s) available over that interface. E.g., if a nameserver at address 1.2.3.4 is available over interface eth0, then add dns-nameservers 1.2.3.4 to the iface eth0 stanza.

If you are using NetworkManager then settings are entered in the Connection Editor (network indicator | Edit Connections. ) in the IPv4 Settings tab.

Doing /etc/init.d/networking restart to reconfigure interfaces is deprecated. If you are using ifup then first ifdown each active network interface, then ifup each interface. If you are using NetworkManager then, first, disable networking using the indicator (top of the desktop); then open a terminal and run

sudo /etc/init.d/network-manager restart 

and then enable networking using the indicator.

Regarding the fact that /etc/init.d/networking restart resulted in

RTNETLINK answers: File exists Failed to bring up eth0 

This means that ifupdown thinks that eth0 is already up. Use ifdown —force eth0 to cause ifupdown to stop believing that it has already configured the interface.

Regarding the «deprecated» message, this message is no longer printed in Ubuntu 12.10 but you should still note that initscripts are «on their way out». To restart a service foo , use service foo restart or restart foo . Note also that if you want to reconfigure your interfaces it is better to ifdown them one by one than to rely on restarting «networking».

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What does the dns-search option mean in /etc/network/interfaces?

I personally disabled this on my server, because I use IPv6, and when an address (f.e. hello.com) I was trying to connect to didn’t support IPv6, the system tried to resolve hello.com.example.com instead and that yielded an IPv6 of the example.com as the result (not IPv4 address of hello.com as expected). I wrote about it in more detail here: daysleeper.cz/…

2 Answers 2

dns-search determines which domain is appended for dns lookups.

Normally you will specify here the same domain as returned by hostname -f .

For detailed information see the following quote from man resolv.conf :

search Search list for host-name lookup. The search list is normally determined from the local domain name; by default, it contains only the local domain name. This may be changed by listing the desired domain search path following the search keyword with spaces or tabs separating the names. Resolver queries having fewer than ndots dots (default is 1) in them will be attempted using each component of the search path in turn until a match is found. For environments with multiple subdomains please read options ndots:n below to avoid man-in-the-middle attacks and unnecessary traffic for the root-dns-servers. Note that this process may be slow and will generate a lot of network traffic if the servers for the listed domains are not local, and that queries will time out if no server is available for one of the domains. The search list is currently limited to six domains with a total of 256 characters. 

Why isn’t the dns-search directive mentioned in the man page for the interfaces file? (manpages.ubuntu.com/manpages/utopic/en/man5/interfaces.5.html)

@odigity, I think it is because it is an option passed to resolvconf, and not an internal feature of ifup.

How does this all hang together with search order as defined in /etc/nsswitch.conf ?? Sounds like multiple cures for the same problem

I also found this in the README.gz located in /usr/share/doc/resolvconf on Ubuntu 14.04. It provides a bit more clarity.

Beware of the resolv.conf file being managed by the service resolvconf.

dns-search appears to be a necessary line in the stanza of a logical interface.

 3.4 ifupdown * Remove any "up" or "down" commands from /etc/network/interfaces that futz with /etc/resolv.conf and remove any scripts from /etc/network/if-*.d/ that futz with /etc/resolv.conf. * For each inet static logical interface through which a nameserver is accessible, add lines like the following to /etc/network/interfaces . dns-nameservers 11.22.33.44 55.66.77.88 dns-search foo.org bar.com Other recognized option words are 'dns-domain' and 'dns-sortlist'. These option names correspond to the option names used in the resolv.conf file with one exception: whereas one lists several nameserver addresses in /etc/resolv.conf on several "nameserver" lines, here one should list them all on a single "dns-nameservers" line. See resolv.conf(5) for more information. The lines entered in /etc/network/interfaces will be added to the resolver configuration file (without the "dns-" prefix, of course) when a physical interface is brought up as that logical interface. Note that the resolver configuration is updated AFTER all the "up" commands have been run; therefore "up" commands cannot make use of nameservers listed on "dns-nameservers" lines in the same logical interface stanza. Changing this will require modifying ifupdown so that it talks to resolvconf; currently resolvconf hooks into ifupdown using the script /etc/network/if-up.d/000resolvconf. Note too that scripts in /etc/network/if-up.d/ CAN make use of the added nameservers because those scripts run after 000resolvconf. 

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How to Set DNS Nameservers on Ubuntu 22.04?

DNS (Domain Name System) is a system that translates human-readable domain names (such as example.com) into numerical IP addresses. Name servers contain the DNS records for a domain and are responsible for answering requests from clients, such as web browsers.

This guide will explain various methods to set the DNS Nameservers on Ubuntu 22.04. The content of this tutorial is mentioned-below:

Let’s start with the CLI method.

Method 1: Using CLI to Set DNS Nameserver

To set the DNS name servers on Ubuntu 22.04 via the command line, users can follow these steps:

Configure resolv.conf file

Open the “/etc/resolv.conf” file in a nano text editor using the “sudo” privileges:

Add a line to the file for each DNS name server you want to use. The line should start with the nameserver with the IP address:

$ nameserver 8.8.8.8 $ nameserver 8.8.4.4

Save the file and exit the text editor.

Verify the DNS Nameservers

To verify the DNS Nameserver, execute the below script with the “sudo” privilege:

The output confirms that DNS nameservers 8.8.8.8 and 8.8.4.4 have been set.

Alternative Method: Configure “01-network-manager-all.yaml” File Via netplan

Netplan is a tool to configure networking on Linux systems. It allows you to specify the DNS nameservers that your system should use to resolve hostnames.

To set the DNS nameservers in Netplan, you need to edit the Netplan configuration file for your network interface. The configuration file is usually located at /etc/netplan/ and has a .yaml file format.

$ sudo nano /etc/netplan/01-network-manager-all.yaml

Here’s an example of how you can set the DNS nameservers in a Netplan configuration file The description of the script is provided below:

network: version: 2 renderer: networkd ethernets: enp0s3: dhcp4: no addresses: [192.168.157.140/24] gateway4: 192.168.157.140 nameservers: addresses: [8.8.8.8,8.8.4.4]

In this example, the nameservers section specifies that the system should use Google’s public DNS servers (8.8.8.8 and 8.8.4.4) to resolve hostnames. Also, the machine’s IP address is “192.168.157.140” with a subnet mask of “24”. The gateway through which traffic flows is “192.168.157.140”.

Once you have edited the configuration file, you can apply the changes by running the following command:

This will update the system’s DNS settings and cause it to use the nameservers specified in the configuration file.

Let’s head over the same method in GUI.

Method 2: Using GUI to Set DNS Nameserver

On Ubuntu, the DNS name servers resolve domain names that can be specified in the network configuration files. These configuration files can be altered following a GUI of Ubuntu which is carried out as follows:

Step 1: Open the Network Settings Window

Press the icon “Network” located at the top right corner of the desktop screen and hit the “Wired Settings” option:

Step 2: Edit Connection

It navigates to the “Network” section in the “Settings” window. Click the “Edit” button on the connection for which you want to set the DNS nameservers:

Step 3: Check the Automatic (DHCP)

In the “IPv4 Settings” tab, check if the “Automatic (DHCP) addresses” is enabled or not. If not, choose the option:

Step 4: Enter the IP Addresses of DNS

Enter the IP addresses of the DNS nameservers in the “DNS Servers” field. Then, press the button “Apply” to save the address:

That is all from the GUI method for setting the DNS Nameservers.

This is how to set DNS Nameservers on Ubuntu 22.04.

Conclusion

In Ubuntu, the Domain NameServers (DNS) can be set using GUI and CLI methods. In GUI, type the IP addresses of the DNS nameservers in the “DNSServers” field using the “NetworkSettings” window. In CLI, add the DNS Nameservers address “(8.8.8.8 and 8.8.4.4)” in the “01-network-manager-all.yaml”, “/etc/resolv.conf” files. This article has explained various ways to set DNS nameservers on Ubuntu.

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