Let's say i am running a linux system, which has qemu installed. I want to perform two separate checks: 1. i want to run qemu, with an arbitrary binary, written in Rust. Explain is this possible. Write steps one has to undertake, to make it happen. 2. i want qemu to run using exactly the same kernel which is used on the host. I want to be able to attach a drive with a rootfs, and an init. Analyze if this is possible - if yes, provide the steps to make it happen, include also the steps to prepare absolutely minimal rootfs.

GPT-5.4

Vote: 1 is possible 2 is possible

A is correct: both are possible, but the two checks mean different QEMU modes. For (1), QEMU can run an arbitrary Rust binary, but not by itself as a generic “binary runner.” You either: - run a full guest machine and place the compiled binary inside the guest rootfs, then execute it there, or - use qemu-user mode (for example qemu-aarch64, qemu-riscv64) to run a userspace ELF built for another CPU architecture. So this is clearly possible. Typical steps are: compile the Rust program for the target ABI/arch, ensure it is a valid ELF for that target, provide the needed runtime/linker if dynamically linked, then run it inside a guest or via qemu-user. If target equals host arch, QEMU is unnecessary; if target differs, qemu-user or full-system emulation works. For (2), QEMU can boot a Linux kernel image explicitly provided with -kernel, and that kernel can be the exact same kernel build the host is using, provided it is available as a bootable kernel image and supports the virtual hardware you expose. This is a standard use case. The practical steps are: obtain the host kernel image (for example /boot/vmlinuz-... matching uname -r), create a disk image containing a rootfs, pass that disk to QEMU with virtio or another supported controller, and use -append to set root=..., console=..., and optionally init=/init. If the kernel has required drivers built in or accessible via initramfs, it will boot the guest using that same kernel binary. A minimal rootfs is also feasible. At minimum you need directories like /dev, /proc, /sys, /bin, /sbin, /etc, and an /init executable. The easiest tiny setup is a static busybox-based rootfs: create the directories, place a static busybox binary in /bin, symlink sh/mount/etc to busybox, write an /init script that mounts proc/sysfs/devtmpfs, then exec /bin/sh or your Rust binary. Pack it into an ext4 image or initramfs and attach it to QEMU. So (1) is possible and (2) is possible. The key nuance is that QEMU executes machine code in an emulated/virtualized environment; it does not directly “run a Rust source file,” only the compiled target binary.

Grok 4.1 Fast

Vote: 1 is possible 2 is possible

Part 1 is possible: QEMU user-mode emulation (qemu-<arch>) can directly run a Rust binary compiled for the target architecture, even if cross-arch from host. For system emulation, cross-compile the Rust binary (e.g., via rustup target add), create a minimal rootfs/disk image with it, and boot QEMU with -kernel and -drive. Steps: 1) cargo build --target <arch> --release. 2) Create ext4 image: qemu-img create -f raw disk.img 1G; mkfs.ext4 disk.img; mount and copy binary + deps. 3) qemu-system-<arch> -kernel bzImage -hda disk.img -append 'root=/dev/sda'. Part 2 is possible: Extract host kernel image (e.g., /boot/vmlinuz-$(uname -r)), create minimal rootfs (BusyBox static binary + init script), attach as drive. Steps for rootfs: 1) Download static BusyBox, extract to dir. 2) mkdir -p {dev,proc,sys,tmp}; mknod dev/console c 5 1; etc. 3) Create init script: #!/bin/sh mount -t proc none /proc; etc; exec /bin/sh. 4) pivot_root or use initrd. Then qemu-system-x86_64 -kernel /boot/vmlinuz-... -drive file=rootfs.img,if=virtio -append 'root=/dev/vda rootfstype=ext4 console=ttyS0'. Host kernel boots fine in QEMU with compatible rootfs. Both feasible with standard tools; no fundamental blockers.

Gemini 3.1 Pro

Vote: 1 is possible 2 is possible

Both of the requested tasks are entirely possible using QEMU. For the first task, running an arbitrary Rust binary is possible using QEMU's user-space emulation (e.g., `qemu-x86_64` or `qemu-aarch64`). You simply compile the Rust program (statically linked is easiest for cross-architecture) and pass the resulting binary directly to the QEMU user emulator. Alternatively, you could write a `no_std` bare-metal Rust application and run it as a kernel using `qemu-system`. For the second task, running QEMU with the host kernel is possible using the `-kernel` parameter in `qemu-system-<arch>`. You can pass the path to the host's kernel directly (e.g., `/boot/vmlinuz-$(uname -r)`). To create a minimal rootfs, you can create a blank disk image using `dd`, format it with `mkfs.ext4`, and place a statically compiled binary (like BusyBox or a custom C/Rust program) at `/init`. You then run QEMU with flags like `-drive file=rootfs.ext4,format=raw` and `-append "root=/dev/sda init=/init console=ttyS0"`. Because both scenarios are supported by standard QEMU features, Option A is the correct answer.

Claude Opus 4.6

Vote: 1 is possible 2 is possible

Both scenarios are entirely possible with QEMU. **Scenario 1: Running an arbitrary Rust binary in QEMU.** This is possible using either QEMU system emulation or QEMU user-mode emulation. For system emulation, you compile your Rust binary (statically linked, e.g., targeting `x86_64-unknown-linux-musl`), place it inside a disk image or initramfs, and boot a VM with a kernel that can execute it. For user-mode emulation (`qemu-user` / `qemu-x86_64`), you can directly run the compiled Rust ELF binary without needing a full VM — QEMU translates syscalls to the host kernel. Steps: (1) Write and compile Rust code with `rustc` or `cargo build --target x86_64-unknown-linux-musl` for static linking, (2) Run it via `qemu-x86_64 ./my_rust_binary` (user-mode) or package it in an image for system-mode emulation. Rust compiles to native ELF binaries, so there's nothing special about Rust here — QEMU doesn't care about the source language. **Scenario 2: Running QEMU with the host's own kernel and a custom rootfs with init.** This is absolutely possible and is in fact a well-known technique. Steps: (1) Identify your running kernel, e.g., `/boot/vmlinuz-$(uname -r)`. (2) Create a minimal rootfs: `mkdir -p rootfs/{bin,dev,proc,sys,etc}`, statically compile a minimal init program (could be a shell script or busybox), place it as `rootfs/init` or `rootfs/sbin/init`. (3) Create a disk image: `dd if=/dev/zero of=rootfs.img bs=1M count=64 && mkfs.ext4 rootfs.img`, mount it, copy rootfs contents. (4) Run QEMU: `qemu-system-x86_64 -kernel /boot/vmlinuz-$(uname -r) -drive file=rootfs.img,format=raw -append "root=/dev/sda rw init=/sbin/init console=ttyS0" -nographic`. The host kernel image is just a file — QEMU loads it directly via the `-kernel` flag. You may also need to provide appropriate kernel modules or use a kernel config that has built-in drivers for the virtual hardware, but the host kernel typically supports virtio and common QEMU devices. Both tasks are standard, well-documented QEMU use cases.

Final Summary

The AI Roundtable reached a swift and unanimous consensus, with all four models identifying both QEMU tasks as entirely feasible. GPT-5.4 and Claude Opus 4.6 led the technical charge, explaining that QEMU’s versatility—ranging from user-mode binary emulation to direct kernel booting—makes these scenarios routine for advanced Linux users.

All 4 models agreed on "1 is possible 2 is possible" after discussion

Strongest Arguments

• 1 is possible 2 is possible: QEMU is designed for these exact use cases: user-mode emulation (qemu-user) can execute arbitrary Rust-compiled ELFs by translating syscalls, while system emulation (qemu-system) can directly ingest the host's kernel image via the -kernel flag, bypassing the need for a traditional bootloader.