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I have CentOS 7.2 (guest in VirtualBox, vagrant box centos/7, no GUI).

I see there is a nameserver in file:

$ cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 10.0.2.3

But how to add or replace with new one?

I have done this manually directly in the network:

$ vi /etc/sysconfig/network-scripts/ifcfg-eth0
PEERDS=no
DNS1=8.8.4.4
DNS2=8.8.8.8

And it works.

But is there any way to do this through nmcli?

P.S. No nmtui installed (in a selected system).

Community
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Kirby
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4 Answers4

64

Here is the command to modify an existing connection.

nmcli con mod $connectionName ipv4.dns "8.8.8.8 8.8.4.4"

connectionName can be found by command: nmcli con. In the question case, it will be "System eth0"

If you want to ignore automatically configured nameservers and search domains, ie the settings passed from DHCP.

nmcli con mod $connectionName ipv4.ignore-auto-dns yes

Finally, to enable the changes, bring the connection down then up:

nmcli con down $connectionName
nmcli con up $connectionName
restart the NetworkManager service (if you don't want be disconnected) : 
service NetworkManager restart

Verify with cat /etc/resolv.conf. You should not edit /etc/resolv.conf manually as it is generated by NetworkManager service, it is likely to get overridden at any given time.

Useful nmcli manual

SebMa
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lauc.exon.nod
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  • Yeah, thx, found it already. A bit edited your answer... But how to replace exist nameserver? – Kirby Oct 22 '16 at 11:02
  • there is "+ipv4.dns" and "ipv4.dns" can be used, but second one (without "+") doesn't replace. – Kirby Oct 22 '16 at 11:04
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    I'd rather use nmtui or if possible the GUI version as well. There is no need to be a command line ninja, if you have a more convenient option which is doing the same thing. – lauc.exon.nod Oct 22 '16 at 13:08
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    @lauc.exon.nod Some options aren't available in nmtui, and you have to use nmcli to get at them. – Michael Hampton Oct 26 '16 at 01:27
  • Link is dead.... – ceving Jan 14 '19 at 16:52
  • This only works for a specific connection. Is there a way to do it for a device instead? For example, on a laptop, I change networks frequently and don't want to update this for every connection. – J.W.F. Jun 28 '19 at 01:08
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    To remove the default ipv4 dns from a device, try "nmcli device mod <> ipv4.ignore-auto-dns yes". – Ben Aveling Nov 25 '20 at 11:57
11

there is good TUI tool developed by red hat named nmtui that you really should try. it is pre-installed on various distros, nowadays, but if it is not on yours, try:

  sudo yum install networkmanager-tui

it uses a curses based text interface - accessible from the command line. nmcli is only especially necessary when writing scripts, and has larger room for error due to the larger variety of possible input.

infinite-etcetera
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7

In addition to setting the ipv4.dns property described above...

To exclude the DHCP provided DNS servers...set the ipv4.ignore-auto-dns property to yes.

nmcli con mod <connectionName> ipv4.ignore-auto-dns yes

To enable the changes, bring the connection down then up:

nmcli con down <connectionName>
nmcli con up <connectionName>

Verify with cat /etc/resolv.conf

Brien
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Just in case I have done a little script to do that automatically (here with google DNS) for every ethernet/wireless connections:

nmcli -g name,type connection  show  --active | awk -F: '/ethernet|wireless/ { print $1 }' | while read connection
do
  nmcli con mod "$connection" ipv6.ignore-auto-dns yes
  nmcli con mod "$connection" ipv4.ignore-auto-dns yes
  nmcli con mod "$connection" ipv4.dns "8.8.8.8 8.8.4.4"
  nmcli con down "$connection" && nmcli con up "$connection"
done

At the end, the wireless connections will be lost. You have to reconnect and voilà !

Yannig Perre
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