Using pi-sbx microVM sandboxes without nested virtualization

pi-sbx keeps Pi on the host and runs its built-in shell and filesystem tools inside a Docker SBX microVM. Workspace changes remain visible on the host.

PVM (Pagetable-based Virtual Machine) lets us run these microVMs inside an x86_64 Linux VM without exposed VMX/SVM or nested virtualization. It still provides the /dev/kvm interface used by SBX.

First, install and boot the PVM host kernel from Porting PVM to Linux 7.2, including its pti=off boot setting. You also need an SBX-compatible PVM guest kernel, saved as vmlinux below.

Install SBX

curl -fsSL https://get.docker.com | sudo REPO_ONLY=1 sh
sudo apt-get install docker-sbx
sudo usermod -aG kvm "$USER"
sudo usermod -aG docker $USER
newgrp kvm
sbx login

Replace the guest kernel

From the directory containing your SBX-compatible PVM guest vmlinux:

wget https://github.com/kholia/linux-builds/raw/refs/heads/master/pvm-host-kernel-debs.zip

wget https://github.com/kholia/linux-builds/raw/refs/heads/master/pvm-full-guest-kernel.zip

unzip pvm-host-kernel-debs.zip

unzip pvm-full-guest-kernel.zip

sudo apt install ./*.deb  # install pvm host kernel and then reboot the host *manually*

sudo cp vmlinux /usr/libexec/nerdbox-kernel-x86_64

sbx daemon restart

Note: Package upgrades can replace this kernel; reinstall it after upgrading SBX.

Install Pi and use the sandbox

Install Pi and the extension:

curl -fsSL https://pi.dev/install.sh | sh
pi install git:github.com/ChristianMoesl/pi-sbx

The extension requires SBX 0.48.0 or newer, plus Node.js, Bash, sh, rg, and file in the sandbox image. Create the sandbox and start Pi from its mounted workspace:

mkdir -p "$HOME/sbx-debug"
sbx --debug create --name sbx-default-test shell "$HOME/sbx-debug"
sbx exec sbx-default-test -- uname -r
cd "$HOME/sbx-debug"

$ sbx run --name sbx-default-test
agent@sbx-default-test:sbx-debug$ uname -a
Linux sbx-default-test-2 7.3.0-gad6ecb3610e2 #1 SMP PREEMPT_DYNAMIC...

cd "$HOME/sbx-debug"

pi

Check that uname -r reports your PVM guest kernel. Pi discovers the sandbox from the workspace mount; its footer should show sbx: sbx-default-test. Use /sbx inside Pi to select or reconnect to it.