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Old 05-06-2020, 10:49 AM   #1
ddenial
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remove nameserver line from resolv.conf

Hello All,

Following is an output of resolv.conf from CentOS 7.8 KVM guest.
Code:
# cat /etc/resolv.conf 
# Generated by NetworkManager
search kvmlab.lan cntnix.lan
nameserver 192.168.122.1
nameserver 192.168.1.7
I want to remove the line 'nameserver 192.168.122.1'. I don't know from where it is appending. I have not mentioned it anywhere.

This is my network config file
Code:
# cat /etc/sysconfig/network-scripts/ifcfg-enp1s0 
TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="enp1s0"
DEVICE="enp1s0"
ONBOOT="yes"
DOMAIN="kvmlab.lan cntnix.lan"
DNS1=192.168.1.7
How do I remove that nameserver from libvirt (192.168.122.1)?

Thanks
 
Old 05-06-2020, 10:56 AM   #2
shruggy
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This is for RHEL 8, but IIRC the RHEL/CentOS 7 is very similar in this respect.
 
Old 05-07-2020, 01:19 AM   #3
chrism01
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Just fyi, 192.168.122.X is the subnet for the built-in VM system (aka kvm), so comes as std.
eg if you run ifconfig, you'll probably see something like
Code:
virbr0    Link encap:Ethernet  HWaddr 52:54:00:AF:7E:4A  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
You could just ignore it.
 
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Old 05-07-2020, 01:24 AM   #4
pan64
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Quote:
Originally Posted by chrism01 View Post
Just fyi, 192.168.122.X is the subnet for the built-in VM system (aka kvm), so comes as std.
eg if you run ifconfig, you'll probably see something like
Code:
virbr0    Link encap:Ethernet  HWaddr 52:54:00:AF:7E:4A  
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
You could just ignore it.
Exactly. With other words: it is automatically configured for you according to your [virtual] network setup. If you wish to modify it most probably you need to [re]configure your bridge virbr0.

By the way: why do you want to remove it?
 
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Old 05-07-2020, 09:31 AM   #5
ddenial
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Quote:
Originally Posted by pan64 View Post
By the way: why do you want to remove it?
Cause I've installed the Bind DNS server on IP 192.168.1.7. As I am learning the DNS server and the KVM guest in question is used for testing the Bind server as an outsider. So every time I 'dig' something, it is resolved by 192.168.122.1 IP, which I don't want to use. I want it to use IP 192.168.1.7 instead of where my DNS server is.

Code:
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 52:54:00:0c:a8:83 brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.78/24 brd 192.168.122.255 scope global noprefixroute dynamic enp1s0
       valid_lft 3372sec preferred_lft 3372sec
    inet6 fe80::cf9f:806f:2faa:e858/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever


# nmap -p 53 192.168.1.7
Starting Nmap 6.40 ( http://nmap.org ) at 2020-05-07 19:52 IST
Nmap scan report for svr.cntnix.lan (192.168.1.7)
Host is up (0.00018s latency).
PORT   STATE SERVICE
53/tcp open  domain

# dig google.com
; <<>> DiG 9.11.4-P2-RedHat-9.11.4-16.P2.el7_8.2 <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57136
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;google.com.			IN	A

;; ANSWER SECTION:
google.com.		177	IN	A	172.217.163.78

;; Query time: 55 msec
;; SERVER: 192.168.122.1#53(192.168.122.1)
;; WHEN: Thu May 07 19:59:09 IST 2020
;; MSG SIZE  rcvd: 55


# cat /etc/resolv.conf
# Generated by NetworkManager
search kvmlab.lan cntnix.lan
nameserver 192.168.122.1
nameserver 192.168.1.7
At least I want 192.168.1.7 to be my primary DNS server.
 
Old 05-07-2020, 09:42 AM   #6
berndbausch
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Quote:
Originally Posted by ddenial View Post
How do I remove that nameserver from libvirt (192.168.122.1)?
My guess: It comes from DHCP. Not sure how that interferes with the DNS1 in the ifcfg file.

Assuming NetworkManager is used in the guest, you could add NM_CONTROLLED=no to ifcfg-xxx. Or set dns=no in /etc/NetworkManager/NetworkManager.conf.
 
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Old 05-07-2020, 10:30 AM   #7
ddenial
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I finally resolved it by adding PEERDNS=no in ifcfg config file.

Thanks everybody.
 
  


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