Tensorlake Documentation

A sandbox created from a CAS image exposes /dev/kvm, so you can run virtual machines inside it with any KVM-based hypervisor. Snapshot-restore and all other features are supported for sandboxes with nested VMs running inside of them. This guide builds an image with QEMU and an Ubuntu cloud image, boots that cloud image as a VM inside a sandbox, and connects to it over SSH.

Build an Image with QEMU

The Dockerfile installs QEMU, virtme-ng, and a kernel for the nested VM:

Dockerfile

FROM tensorlake/cas/ubuntu-systemd

ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update \
    && apt-get install -y --no-install-recommends \
        virtme-ng qemu-system-x86 linux-image-virtual \
        binutils busybox-static zstd \
    && rm -rf /var/lib/apt/lists/*

tl sbx image create /tmp/nested-virt-guide/Dockerfile --registered-name nested-virt --cas --disk_mb 20480

Create the Sandbox and Check KVM

Create the sandbox with enough CPUs, memory, and disk for the VM, then confirm the KVM device is there. The QEMU packages make /dev/kvm owned by root:kvm, so the commands in this guide run as root:

SANDBOX_ID=$(tl sbx create --image nested-virt --cpus 4 --memory 8192 --disk_mb 30720)
tl sbx exec $SANDBOX_ID --user root -- ls -l /dev/kvm

Boot a VM

vng boots the installed kernel under QEMU with KVM acceleration from the sandbox’s own filesystem, runs a command inside the VM, and shuts it down. The output is the VM’s kernel, not the sandbox’s:

tl sbx exec $SANDBOX_ID --user root -- bash -c 'vng -v -r /boot/vmlinuz-* --exec "uname -a"'

CAS Images

The image format that exposes KVM inside a sandbox.

Snapshot and Clone

Save and restore a sandbox with its running VM.

Live Resize

Give a running sandbox more CPUs and memory for its VMs.

Overview

Guides

Use Cases

Nested Virtualization

Build an Image with QEMU

Create the Sandbox and Check KVM

Boot a VM

See Also

CAS Images

Snapshot and Clone

Live Resize

​Build an Image with QEMU

​Create the Sandbox and Check KVM

​Boot a VM

​See Also

CAS Images

Snapshot and Clone

Live Resize

Build an Image with QEMU

Create the Sandbox and Check KVM

Boot a VM

See Also