[CoreOS]Where does NetworkManager get dns-search domain?

Question

Bug?

Host Operating System Version

CentOS8

Target Operating System Version

rhcos-4.9.0-x86_64 (VM)

Environment

This is simple architecture of mine, I tried to install coreos on vm(10.10.12.20) and that vm look at the server(dnsmasq) as nameserver.
I used coreos-installer with ignition file to set up RedHat CoreOS.

Dnsmasq

dnsmasq.conf

interface=enp1s0

address=/.apps.blue.garagekr.com/10.10.12.12 #loadbalance
host-record=bastion.blue.garagekr.com,10.10.12.12

dhcp-option=3,10.10.12.1        # Gateway
dhcp-option=6,10.10.12.12 # Nameserver
dhcp-range=10.10.12.0,static
dhcp-authoritative

host-record=master2.blue.garagekr.com,10.10.12.20

#reverse
ptr-record=20.12.10.10.in-addr.arpa.,master2.blue.garagekr.com
...

CoreOS

In CoreOS Installation Step, I set up network using nmtui (only setting ip, nameserver, gateway) and used this command:

sudo coreos-installer install --copy-network --ignition-url=http://10.10.12.12:8080/bootstrap.ign --insecure-ignition /dev/sda

Problem

CoreOS installation ended up without any issues, But the problem is DNS search. I didn't write down any configuration of dns search. where dns search domain came from??

oddly, NetworkManager of CoreOS doesn't have dns search option in keyfile(/etc/NetworkManager/system-connections) .

[root@master2 /]# NetworkManager --print-config
# NetworkManager configuration: /etc/NetworkManager/NetworkManager.conf (lib: 10-disable-default-plugins.conf, 20-client-id-from-mac.conf) (etc: 20-keyfiles.conf, sdn.conf)

[main]
# rc-manager=symlink
# auth-polkit=true
# dhcp=internal
plugins=keyfile,ifcfg-rh

[keyfile]
path=/etc/NetworkManager/system-connections

[logging]
# backend=journal
# audit=false

[device]
match-device=interface-name:br-int;interface-name:br-local;interface-name:br-nexthop,interface-name:ovn-k8s-*,interface-name:k8s-*;interface-name:tun0;interface-name:br0;driver:veth
managed=0

[connection]
ipv4.dhcp-client-id=mac

# no-auto-default file "/var/lib/NetworkManager/no-auto-default.state"

[root@master2 /]# ls /etc/NetworkManager/system-connections/
'Wired connection 1.nmconnection'

[root@master2 /]# cat /etc/NetworkManager/system-connections/Wired\ connection\ 1.nmconnection
[connection]
id=Wired connection 1
uuid=4eace183-cd66-3e30-9391-06813f952009
type=ethernet
autoconnect-priority=-999
interface-name=enp1s0
permissions=
timestamp=1655879214

[ethernet]
mac-address-blacklist=

[ipv4]
address1=10.10.12.20/24,10.10.12.1
dns=10.10.12.12;
dns-search=
method=manual

[ipv6]
addr-gen-mode=stable-privacy
dns-search=
method=auto

[proxy]

dns-search is empty!!

But the /etc/resolv.conf is like this:

[root@master2 /]# cat /etc/resolv.conf
# Generated by NetworkManager
search blue.garagekr.com
nameserver 10.10.12.12

Question is:

1. Where does NetworkManager get dns-search domain? (from Ignition?)
2. Is there any way to remove dns-search? (In the coreos installation step)

Thanks!

Answer 1

nmcli connection modify Network_InterfaceName ipv4.dns-search (searchDomainname- for multiple entry you can use comma)