/etc/resolver/dhcp_host_domain_ng.py causes high load

Script /etc/resolver/dhcp_host_domain_ng.py is run by DNS resolver. Read dhcp leases and creates some dynamic hosts like file. We have ethers with about 150 records and dynamically we lease about another 150 addresses.

The load is sometimes above 50 when this script is running!!! It runs in many instances/processes simultaneously.

Router becomes unreachable for several minutes. Sometimes several times a day, sometimes it works in this load sufficiently.

The only workaround for me now is disable this script putting sys.exit(0) at the start (if __name…).

I switched from kresd to unbound without any effect.

Hardware: Turris Omnia
OS: /etc/turris-version 6.2.3

Has anybody similar experiences and solution?

Thank you very much.


1 Like


same issue High CPU usage with Unbound on Omnia

Am also desperately looking for a solution. I have a lot of static DHCP leases, so turning off DHCP clients in reForis is not an option.

Can you please show how exactly you put that sys.exit(0) into the script?

I did several changes:

1. /etc/init.d/resolver - here I changed variable DHCP_SCRIPT not to be the script run:


2. /etc/hotplug.d/dhcp/40-dynamic-domains
exit 0 # at the beginning of the script under #!/bin/sh line

3. /etc/resolver/dhcp_host_domain_ng.py
sys.exit(0) # at the beginning of the script under #!/usr/bin/python3 line

After these modifications is load under 0.10 almost all time.

I know this solution is to be rewritten after update of packages installing these files. Then these modification I have to do again.

It would be nice to disable this script by resolver using a config parameter :slight_smile:

I’m curious if the ouptut provided by dhcp_host_domain_ng.py is actually used. It’s sense is more non-sense. It produces hosts like file from current dhcp leases.

I hope somebody from Turris provides non-workaround solution for us here :slight_smile: Thanks in advance.


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Thanks a lot, I will apply all these workarounds.

It’s really a devastating issue, I am currently using my mobile connection for audio calls as Omnia cannot provide a stable connection on my home line.

Please Turris Team, find a way to fix this issue.

I wonder if it would work to instead uncheck the “DHCP clients in DNS” in reforis/network-settings/dns (as a simpler workaround)

So what exactly would that do? All my devices (about 100) have a static assignment. I don’t want to risk them not being accessible via hostname. Is it safe to uncheck that option? What does it even do?

If you dont use Knot-Resolver(kresd) you can do this

Edit /etc/hotplug.d/dhcp/40-dynamic-domains

and add exit 0 as 2nd line as below.

exit 0
export ACTION
export MACADDR
export IPADDR

python3 /etc/resolver/dhcp_host_domain_ng.py "$@"
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I’m afraid I don’t recall details around the DHCP names.

It seems this was sufficient to fix the issue :+1:

Are there any downsides in keeping it like that? Will this get overridden by a TOS update?

The whole point of the script is to get dynamic names from DHCP to resolve in DNS (name.lan by default), so you’ll certainly lose that. That’s what the reForis checkbox does as well. It does not turn off DHCP but just transport of DHCP names to DNS.

I don’t think any downsides. Not sure but might be overwritten by update.

It just populates a file for Knot-resolver


Hmm shortly after it seemed fixed, it happened again. 100% load on both cores, disrupting the whole network.

I now did all the modifications v.matys mentioned and also did a chmod -x on the scripts.

Any information from turris team on this issue yet?

Did you check what’s causing the high CPU load now that you disabled the call to /etc/resolver/dhcp_host_domain_ng.py? Did you terminate the existing instances of that script after making the changes, e.g., by rebooting your router?

This only happens occasionally, all these processes spawn, consuming all available CPU cycles. This lasts for about a minute or two, then the processes disappear and network is usable again.

I did not terminate any processes by hand, neither did I reboot the router yet.

Well… still happening. And I think I can pin that down to when a device joins my network:

When I connect a new WiFi device
When I wake up my PC from sleep

Then this happens.

Did you terminate these roguie processes in the meantime? If not, please do so by, e.g., restarting the router.

If you then can still reproduce the issue press F5 for a tree view which should show you which parent process it is that calls /etc/resolver/dhcp_host_domain_ng.py.

Ok, I’m an idiot. I made a backup of the file 40-dynamic-domains in the same folder /etc/hotplug.d/dhcp before changing it. So there was still a file with the original content :roll_eyes:

Moved it away now. Let’s see if that helps.

Just updated to 6.2.4 via reForis.

40-dynamic-domains has not been replaced, the exit 0 is still there.

Everything works fine so far, all my local hostnames are resolvable.

Turris Team, please comment on this issue. Is this a bug? Will it be fixed? I would prefer a non-workaround solution which is not subject to potentially break things on updates.