Hi Kolla team, I've been troubleshooting an issue for weeks and would really appreciate your insight. *Environment:* - Kolla-Ansible 2025.1 (Epoxy) all-in-one - Ubuntu 24.04 on VM (nested virtualization) - OpenStack services seem healthy (nova-compute, neutron, etc. all up) *The Problem:* Any attempt to create a VM (even a tiny Cirros test VM) fails with: text libvirt.libvirtError: cannot fork child process: Resource temporarily unavailable *What Works:* - ✅ Can create networks, subnets, routers, keypairs via CLI - ✅ Direct qemu-system-x86_64 -enable-kvm test succeeds - ✅ /dev/kvm exists with correct permissions - ✅ KVM modules loaded (kvm_intel), nested virt enabled (Y) *Resource Limits (all seem fine):* - RAM: 88 GB, vCPUs: 32 - pid_max: 4,194,304 - kernel.threads-max: 722,077 - ulimit -u: 361,038 - Total host threads: ~111k (well below limits) *Container-Specific Checks:* - nova_compute: pids.max=108k, Max processes=unlimited, only 27 PIDs running - nova_libvirt: No explicit PidsLimit (<nil>), logs not showing obvious errors - Libvirt volume only 12KB (no runaway logs) - Host libvirtd is inactive (no conflict) *What I've Tried:* - Recreated networks/routers multiple times - Restarted containers - Verified all endpoints are correctly set to VIP (192.168.58.50) - Checked kernel logs – no relevant errors *Full error from nova-compute log:* text libvirt.libvirtError: cannot fork child process: Resource temporarily unavailable Has anyone encountered this in an all-in-one deployment where all obvious limits are huge but libvirt still refuses to fork? Could it be a cgroup v2 limit I'm missing, or something in the libvirt container configuration? Any pointers would be hugely appreciated. Thanks, Dennis