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Additionally to the selected DNS servers AdGuard Home uses default DNS Server of linux in which it is running #7834

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@Florian3434

Description

@Florian3434

Prerequisites

Platform (OS and CPU architecture)

Linux, AMD64 (aka x86_64)

Installation

GitHub releases or script from README

Setup

On one machine

AdGuard Home version

v0.107.61

Action

AdGuard Home is set up normally and in normal use. Several times a day it hangs blocking DNS in the entire network.

Expected result

AdGuard working normally using exactly the upstream DNS servers set up in UI settings -> DNS settings.

Actual result

AdGuard Home is using the router IP additionally to the selected DNS servers. It hangs with high cpu usage and writing activity because of DNS lookup loop.

Additional information and/or screenshots

top returns high CPU usage:

17:57:34 up 4:34, 1 user, load average: 0.00, 0.00, 0.00
Tasks: 16 total, 1 running, 15 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.9 us, 0.6 sy, 0.0 ni, 98.2 id, 0.1 wa, 0.0 hi, 0.2 si, 0.0 st
MiB Mem : 4096.0 total, 3656.2 free, 128.9 used, 310.9 buff/cache
MiB Swap: 4096.0 total, 4096.0 free, 0.0 used. 3967.1 avail Mem

PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND        
**222 root      20   0 1334916 122416  18560 S   1.3   2.9   1:36.60 AdGuardHome**    
 53 root      20   0  307260 237604 236836 S   0.7   5.7   0:19.22 systemd-journ+ 
  1 root      20   0  167644  11520   8832 S   0.0   0.3   0:00.25 systemd        
 89 systemd+  20   0   18036   8448   7424 S   0.0   0.2   0:00.06 systemd-netwo+ 
112 root      20   0    3604   2048   1920 S   0.0   0.0   0:00.01 cron           
117 message+  20   0    9136   4480   4096 S   0.0   0.1   0:00.02 dbus-daemon    
125 root      20   0   16584   7552   6656 S   0.0   0.2   0:00.06 systemd-logind 
230 root      20   0    2520   1536   1536 S   0.0   0.0   0:00.00 agetty         
234 root      20   0    6128   3712   3328 S   0.0   0.1   0:00.00 login          
235 root      20   0    2520   1536   1536 S   0.0   0.0   0:00.00 agetty         
246 root      20   0   15440   9216   7936 S   0.0   0.2   0:00.01 sshd           
377 root      20   0   42664   4716   4096 S   0.0   0.1   0:00.04 master         
379 postfix   20   0   43096   6912   6272 S   0.0   0.2   0:00.00 qmgr           
387 root      20   0    4984   4096   2816 S   0.0   0.1   0:00.00 bash           
390 root      20   0    8568   4608   2688 R   0.0   0.1   0:05.73 top            

journalctl -u AdGuardHome.service returns endless entries like this (total size 2.9 GB):

May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.394282 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.394390 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.401963 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.402034 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.403194 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.403242 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.404315 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.404360 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.404319 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.404430 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.405586 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.405650 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.406737 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.406804 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.407738 ERROR response received addr=192.168.179.1:53 proto=udp status="e>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.407809 [error] dnsproxy: exchange failed upstream=192.168.179.1:53 quest>
May 17 19:29:10 AdGuard AdGuardHome[210]: 2025/05/17 19:29:10.408952 ERROR response received addr=192.168.179.1:53 proto=udp status="e>

cat /etc/systemd/journald.conf (proxmox console/terminal) returns these linux DNS settings:

--- BEGIN PVE ---

search local
nameserver 192.168.179.1

--- END PVE ---

Of course, the router 192.168.179.1 is configured to send dns queries to AdGuard, so it is caught in a loop blocking DNS in the entire network.

Temporary solution:
Change linux DNS settings to a different server using nano /etc/systemd/journald.conf, e.g.:

--- BEGIN PVE ---

search local
nameserver unfiltered.adguard-dns.com

--- END PVE ---

restart AdGuardHome:
systemctl restart AdGuardHome

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