Deploying and Running NetBSD on QEMU/KVM

The NetBSD operating system is renowned for its portability, modular design, and clean codebase; its famous slogan "Of course it runs NetBSD" bears testament to its ability to run across dozens of hardware architectures. In modern Linux infrastructure and virtualization environments (based on KVM), achieving optimal performance with NetBSD requires proper configuration of hardware acceleration, high-throughput paravirtualization drivers (the VirtIO suite), and appropriate serial or graphical console management.

In this technical guide, we walk through setting up NetBSD 10.x on QEMU/KVM—from creating disk images and configuring performance flags to completing installation and essential post-install setup.

1. Preparing the Disk Image (qcow2 Format)

For optimal storage performance and to leverage thin provisioning capabilities, create a virtual disk in qcow2 format:

qemu-img create -f qcow2 netbsd.qcow2 20G

2. Launching the Virtual Machine with Optimized Flags (KVM + VirtIO)

To achieve maximum I/O and CPU throughput, utilize the virtio-net and virtio-blk paravirtualized drivers, which are natively supported in modern NetBSD kernels:

qemu-system-x86_64 \
    -enable-kvm \
    -m 2048 \
    -smp 2 \
    -cpu host \
    -drive file=netbsd.qcow2,if=virtio,format=qcow2,cache=none \
    -cdrom NetBSD-10.0-amd64.iso \
    -boot d \
    -netdev user,id=net0,hostfwd=tcp::2222-:22 \
    -device virtio-net-pci,netdev=net0 \
    -display default

Key architectural flags in this command: * -cpu host and -enable-kvm: Direct pass-through of physical CPU instruction sets without software emulation overhead. * if=virtio and virtio-net-pci: Bypasses emulation layers of legacy IDE or e1000 adapters, utilizing high-speed VirtIO bus communication. * hostfwd=tcp::2222-:22: Forwards host port 2222 to guest SSH port 22 for convenient remote access without requiring network bridge setup.

3. Installation Steps via sysinst

Once the ISO boots, you enter the curses-based NetBSD installer, sysinst:

1. Select language: a: Installation in English.
2. Choose a: Install NetBSD to hard disk.
3. Confirm the detected disk device (typically ld0 for the VirtIO block device).
4. Select partitioning scheme according to your firmware (MBR partitions for standard BIOS or GPT for UEFI).
5. Format the filesystem as FFSv2 with logging support enabled (WAPBL) to prevent lengthy fsck scans upon unexpected shutdowns.
6. Choose the default package set (Full installation) and proceed with extracting installation sets from the install media.

4. Post-Installation & SSH Configuration

Before rebooting, perform these essential steps in the post-install configuration menu:

• Set root password: Choose a strong password for administrative access.
• Add an operational user: Create an unprivileged user and add them to the wheel group for administrative tasks.
• Enable SSH daemon (sshd): If not enabled during install, append to /etc/rc.conf:

sshd=YES

The VirtIO network interface is recognized as vioif0. Configure dynamic IP allocation via DHCP in /etc/rc.conf:

ifconfig_vioif0="dhcp"

5. Final Boot Without Installation Media

After installation completes, shut down the VM, detach the installation media, and boot permanently from disk:

qemu-system-x86_64 \
    -enable-kvm \
    -m 2048 \
    -smp 2 \
    -cpu host \
    -drive file=netbsd.qcow2,if=virtio,format=qcow2,cache=none \
    -netdev user,id=net0,hostfwd=tcp::2222-:22 \
    -device virtio-net-pci,netdev=net0 \
    -nographic

Tip for headless server setups: Passing the -nographic flag along with redirecting NetBSD's console to com0 in /boot.cfg allows full serial console interaction right inside your host Linux shell TTY without any graphic window dependencies.