October 2026 - Users - libvirt List Archives

[FOSDEM] Call for participation: Virtualization and Cloud infrastructure Room at FOSDEM 2027
by Piotr Kliczewski 26 Oct '26

26 Oct '26

We are excited to announce that the call for proposals is now open for the Virtualization and Cloud infrastructure devroom at the upcoming FOSDEM 2027, to be hosted on January 30th (Saturday). This devroom is a collaborative effort, and is organized by dedicated folks from projects such as OpenStack, Xen Project, KubeVirt, QEMU, KVM, and Foreman. We invite everyone involved in these fields to submit your proposals by November 23rd. About the Devroom The Virtualization & IaaS devroom will feature session topics such as open source hypervisors or virtual machine managers such as Xen Project, KVM, bhyve and VirtualBox as well as Infrastructure-as-a-Service projects such as KubeVirt, Apache CloudStack, OpenStack, QEMU and OpenNebula. This devroom will host presentations that focus on topics of shared interest, such as KVM, libvirt, shared storage, virtualized networking, cloud security, clustering and high availability, interfacing with multiple hypervisors, hyperconverged deployments and scaling across hundreds or thousands of servers. Presentations in this devroom will be aimed at developers working on these platforms who are looking to collaborate and improve shared infrastructure or solve common problems. We seek topics that encourage dialog between projects and continued work post-FOSDEM. Important Dates Submission deadline: 23rd of November Acceptance notifications: 1st of December Final schedule announcement: 7th of December Devroom: 30th of January (Saturday) Submit Your Proposal During submission [1] please make sure to select Virtualization and Cloud infrastructure from the Track list. Please provide a meaningful abstract and description of your proposed session. Submission Guidelines We expect more proposals than we can possibly accept, so it is vitally important that you submit your proposal on or before the deadline. Late submissions are unlikely to be considered. All presentation slots are 30 minutes, with 20 minutes planned for presentations, and 10 minutes for Q&A. All presentations will be recorded and made available under Creative Commons licenses. In the Submission notes field, please indicate that you agree that your presentation will be licensed under the CC-By-SA-4.0 or CC-By-4.0 license and that you agree to have your presentation recorded. For example: "If my presentation is accepted for FOSDEM, I hereby agree to license all recordings, slides, and other associated materials under the Creative Commons Attribution Share-Alike 4.0 International License. Sincerely, Piotr Kliczewski and Tal Nisan In the Submission notes field, please also confirm that if your talk is accepted, you will be able to attend FOSDEM and deliver your presentation. We will not consider proposals from prospective speakers who are unsure whether they will be able to secure funds for travel and lodging to attend FOSDEM. (Sadly, we are not able to offer travel funding for prospective speakers.) Code of Conduct Following the release of the updated code of conduct for FOSDEM[2], we'd like to remind all speakers and attendees that all of the presentations and discussions in our devroom are held under the guidelines set in the CoC and we expect attendees, speakers, and volunteers to follow the CoC at all times. If you submit a proposal and it is accepted, you will be required to confirm that you accept the FOSDEM CoC. If you have any questions about the CoC or wish to have one of the devroom organizers review your presentation slides or any other content for CoC compliance, please email us and we will do our best to assist you. Questions? If you have any questions about this devroom, please send your questions to our devroom mailing list. You can also subscribe to the list to receive updates about important dates, session announcements, and to connect with other attendees. See you all at FOSDEM! [1] https://fosdem.org/submit [2] https://fosdem.org/2027/practical/conduct/ <https://fosdem.org/2026/practical/conduct/>

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Default nftables libvirt_network table results in prerouting not working
by fc26wuqa＠studserv.uni-leipzig.de 26 Oct '26

26 Oct '26

Hi, I just set up a new KVM Server, everything seems to work, but prerouting to guests. I created a guest (192.168.121.2) (which I can access via virt-manager), where I want to route my SSH traffic to. Its using the default network. I created a prerouting and postrouting chain in my nftables.conf. 172.18.68.11 is the KVM supervisor, and 192.168.121.0/24 is its guest network. virbr0 is the guest network and bond0 is the supervisor network. When I only load the rules in nftables everything works fine, but when I restart libvirtd then (thus loading the default rules in such as the libvirt_network table) the forwarding failes with ssh: connect to host 172.18.68.11 port 22: Connection refused. When I delete the forward chain in the default libvirt_network rules everything works again. The foward chain consists of """ chain forward { # handle 33 type filter hook forward priority filter; policy accept; counter packets 9 bytes 500 jump guest_cross # handle 36 counter packets 9 bytes 500 jump guest_input # handle 35 counter packets 0 bytes 0 jump guest_output # handle 34 } """ Can someone have a look at my ruleset? https://bin.disroot.org/?5924a197c67e0016#362YmVtB8bjehtLVZb8Qf856VxMJR14UU… (up until table libvirt_network its my nftables.conf, under that its the rules that get loaded in with the libvirtd daemon) Am I doing something wrong, when I create a new prerouting chain?

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[libvirt-users] bridge / ubuntu / no arp reply
by François Chenais 15 Oct '26

15 Oct '26

Hello I'm trying to setup a bridged guest on an ubuntu 13.10 but it doesn't work. (Everything is ok with NAT) Network sniffing shows that arp replies don't come back to the guest. Test 1 ------ Guest : ping host_bridge_ip (ok) Test 2 ------ Guest: ping other_lan_host (KO) other_lan_host - receives arp who-is request - sends arp reply - arp -a shows the guest macaddr => Guest doesn't receive reply Test 3 ------ other_lan_host ping the Guest (KO) - arp -a shows "incomplete" addr - Guest receives nothing On Host ------- network tcpdump on bridge or vnet interfaces shows request but no reply ... Thanks in advance for help or ideas François

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does the 'bandwidth' work?
by lejeczek 09 Oct '26

09 Oct '26

Hi guys. I have a network like so: <network> <name>10_1_1</name> <uuid>864fb78e-0fb0-4c32-bb47-0e5ac68d9491</uuid> <forward mode='bridge'/> <bridge name='nm-bridge1011'/> <bandwidth> <inbound average='610351' peak='620000'/> <outbound average='610351' peak='620000'/> </bandwidth> </network> I'd expect this to limit network to 10Gbs - since this is in kibibytes - I assume these two add to make the max? But when I _iperf3_ in guests then I get speeds near host's native, which are much higher than expected limit. Am I missing something - no <bandwidth> in guests - or there actually might be an issue here? I'm on Centos10 with libvirt-12.8.0-1.el10 thanks, L.

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When libvirt would start dnsmasq?
by lejeczek 08 Oct '26

08 Oct '26

Hi guys. Under what circumstances libvrirt would start _dnsmasq_ on it's own? I certainly did not plan for libvirt to manage dhcp but sometimes I find: -> $ netstat -utapn | grep \:67 udp 0 0 0.0.0.0:67 0.0.0.0:* 19678/dnsmasq -> $ ps -Fp 19678 UID PID PPID C SZ RSS PSR STIME TTY TIME CMD dnsmasq 19678 1 0 2258 1824 8 Oct07 ? 00:00:00 /usr/sbin/dnsmasq --conf-file=/var/lib/libvirt/dnsmasq/default.conf --leasefile-ro --dhcp-script=/usr/libexec/libvirt_leaseshelper which... does fcuk up my main (should be the only) DHCP server. Is it possible to tell libvirt not to do that no matter the circumstances? (or it's not libvirt?) many thanks, L.

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