github.com• Aug 18, 2026• 1 min read
Show HN: K7d – Fork live Kubernetes clusters in GRPO-train AI on infraHey HN, Gary here.Today I want to present k7d which is an Apache 2.0, tight Rust VMM + shim enabling something not possible before: fast forking of live running virtualized multi-node k8s clusters with surviving of in-flight connections.A 3-VM nodes K8s cluster gets forked in 105ms, and a 50x fork of a 3-VM cluster in 4.1s on a 64GB RAM box.I have two goals here:1) enable large scale GRPO/RL training of AI on Kubernetes infra, which IMO is a great playground for reasoning training, besides training a capability that's actually useful. And this requires not only fast episode reset (as you need tens of thousand of multi-turn runs during RL post-training) but also greatly benefits from fast forking so you can do parallel branch exploration, rollback, pruning during RL training. Faithful forks also give you byte-identical starts for the G of GRPO, which gives variance reduction across the group.2) enable
