Message ERROR (dnsmsq) during installation of Kura 5.6.0 in Ubuntu 22.04.5 LTS

[alexcorvis84]

Hello,

I've tried to install Kura 5.6.0 in Ubuntu 22.04 LTS.

I could see in the log the following error during the installation:

Setting up dnsmasq (2.90-0ubuntu0.22.04.1) ...
Created symlink /etc/systemd/system/multi-user.target.wants/dnsmasq.service → /lib/systemd/system/dnsmasq.service.
Job for dnsmasq.service failed because the control process exited with error code.
See "systemctl status dnsmasq.service" and "journalctl -xeu dnsmasq.service" for details.
invoke-rc.d: initscript dnsmasq, action "start" failed.
× dnsmasq.service - dnsmasq - A lightweight DHCP and caching DNS server
     Loaded: loaded (/lib/systemd/system/dnsmasq.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Tue 2025-09-23 10:32:46 UTC; 7ms ago
    Process: 3223 ExecStartPre=/etc/init.d/dnsmasq checkconfig (code=exited, status=0/SUCCESS)
    Process: 3231 ExecStart=/etc/init.d/dnsmasq systemd-exec (code=exited, status=2)
        CPU: 31ms

Sep 23 10:32:46 sentinel systemd[1]: Starting dnsmasq - A lightweight DHCP and caching DNS server...
Sep 23 10:32:46 sentinel dnsmasq[3231]: dnsmasq: failed to create listening socket for port 53: Address already in use
Sep 23 10:32:46 sentinel dnsmasq[3231]: failed to create listening socket for port 53: Address already in use
Sep 23 10:32:46 sentinel dnsmasq[3231]: FAILED to start up
Sep 23 10:32:46 sentinel systemd[1]: dnsmasq.service: Control process exited, code=exited, status=2/INVALIDARGUMENT
Sep 23 10:32:46 sentinel systemd[1]: dnsmasq.service: Failed with result 'exit-code'.
Sep 23 10:32:46 sentinel systemd[1]: Failed to start dnsmasq - A lightweight DHCP and caching DNS server.

Seems that it failed to install because Ubuntu is already using that port 53 by another service, specifically, systemd-resolved is using that port (active by default in Ubuntu 22.04).

So my question is, Is there a problem for Kura if the service dnsmasq is deactivated? or do I need to deactivate the systemd-resolved?

Thanks in advance!

[mattdibi]

Hi there @alexcorvis84,

thanks for reporting the issue. IIRC Kura uses dnsmasq as preferred DNS client therefore disabling systemd-resolved should fix the issue.

I don't remember if this issue came up in the past already 🤔 I need to look into it.

[marcellorinaldo]

@alexcorvis84 to see which processes are using port 53 UDP you can issue:

netstat -ulpn

Usually named (installed by bind) should be the service that is using the 53 port. If dnsmasq is using it, I would check for any pre-existing configuration (under /etc/dnsmasq.conf and /etc/dnsmasq.d/).

As you mentioned, systemd-resolved can also be the one using it. Our installer is disabling systemd-resolved stub listener on 53 at https://github.com/eclipse-kura/kura-networking/blob/f6f56aee2d6888381ded11e1d210c2349774465d/distrib/src/main/resources/scripts/kura_network_install.sh#L179

For further reference:

• https://wiki.archlinux.org/title/Systemd-resolved
• https://unix.stackexchange.com/questions/548830/whats-the-difference-between-run-systemd-resolve-stub-resolv-conf-and-run-sys

[alexcorvis84]

Hi @mattdibi @marcellorinaldo

Finally I decided to disable dnsmasq and leave systemd-resolved enabled. This way it worked for me. Thanks

[marcellorinaldo]

Please be aware that probably our DHCP server manager will still start dnsmasq usign systemd (see here) when putting an interface in DHCP server mode, if dnsmasq is present on the system

[alexcorvis84]

Ok, thanks for the heads up!

[alexcorvis84]

Hi @marcellorinaldo,

Sorry to bother you again, but I noticed that the installer from the Kura version I'm using (5.6.0), stop and disable dnsmasq service and then later on it installs dnsmasq default configuration, but can´t find where's enabled it again... 🤔

So, just to confirm, is dnsmasq the preferred DNS client for Kura 5.6.0 (and onwards)?

Thanks in advance.

[marcellorinaldo]

Hi @alexcorvis84! Yes, dnsmasq is the preferred DHCP server on Kura 5.6.0 and onwards. Prior 5.6.0, dhcpd is preferred. dnsmasq is not enabled but started here: https://github.com/eclipse-kura/kura-networking/blob/4afeed35d287a799696fa27ba1e2859b8a47db60/bundles/org.eclipse.kura.linux.net/src/main/java/org/eclipse/kura/linux/net/dhcp/server/DnsmasqTool.java#L89. It is disabled by the installer to let Kura have control over its lifecycle.

[mattdibi]

So, just to confirm, is dnsmasq the preferred DNS client for Kura 5.6.0 (and onwards)?

I'm sorry I was tired and got confused.

We use dnsmasq as DHCP server. You can find the code enabling it here:

kura/kura/org.eclipse.kura.linux.net/src/main/java/org/eclipse/kura/linux/net/dhcp/DhcpServerManager.java

Line 61 in 410a0ef

if (LinuxNetworkUtil.toolExists(DhcpServerTool.DNSMASQ.getValue())) {

[mattdibi]

Argh @marcellorinaldo beat me to it

[alexcorvis84]

Oh, okay, now I understand the confusion.... I thought dnsmasq was the primary DNS service for Kura, but it turns out it's for DHCP then.

So, on my system (Ubuntu 22.04), the installer should disable systemd-resolved and leave dnsmasq as the main service for DNS and DHCP. (That's how I currently have it configured.) Am I correct?

Thanks in advance

[marcellorinaldo]

dnsmasq is used only for DHCP server, not for DNS resolving. The DNS resolving is actually done by network manager.