How to deploy a NixOS VM via virt-installer

Launching the VM instance

1. Launch a new machine via virt-install, using the Ignition file with your customizations.

   source .env
   virt-install --connect="qemu:///session" --name="${VM_NAME}" --vcpus="${VCPUS}" --memory="${RAM_MB}" \
       --os-variant="nixos-21.05" --import --graphics=none \
       --disk="size=${DISK_GB},path=$HOME/.local/share/libvirt/images/${VM_NAME}-disk1.qcow2" \
       --network="model=virtio,bridge=virbr0,mac=${MAC_ADDR}" \
       --cdrom=${ISO} --livecd

2. Select boot option for serial console

   You may not see the Boot menu. If this is the case press ESC ENTER or ESC and enter 'boot-serial' to directly boot.

   ┌──────────────────────────────────────────────────────────────────────────────┐
   │                                    NixOS                                     │
   ├──────────────────────────────────────────────────────────────────────────────┤
   │ NixOS 21.11.336824.ccb90fb9e11 Installer                                     │
   │ NixOS 21.11.336824.ccb90fb9e11 Installer (nomodeset)                         │
   │ NixOS 21.11.336824.ccb90fb9e11 Installer (copytoram)                         │
   │ NixOS 21.11.336824.ccb90fb9e11 Installer (debug)                             │
   │*NixOS 21.11.336824.ccb90fb9e11 Installer (serial console=ttyS0,115200n8)*    │
   │ Memtest86+                                                                   │
   └──────────────────────────────────────────────────────────────────────────────┘
   

3. enable ssh access

   # generate ss keys
   ssh-keygen -t ed25519 -a 100 -f /home/nixos/.ssh/id_ed25519 -P ''
   
   # install some tools
   nix-env -f '<nixpkgs>' -iA vim
   
   # print ip address
   ip addr | grep 'state UP' --after-context=2 | sed -r -n -e 's/.*inet ([^/]*).*/\1/p'
   
   # set nixos password
   passwd

4. connect via ssh to VM

   replace with the actual ip address.

   ssh nixos@<IP-ADDR>

Installing NixOS from liveCD

1. Partitioning and formatting (MBR)

   # create root partition and 4 GiB swap space
   sudo parted /dev/vda -- mklabel msdos
   sudo parted /dev/vda -- mkpart primary 1MiB -4GiB
   sudo parted /dev/vda -- mkpart primary linux-swap -4GiB 100%
   
   # format partitions
   sudo mkfs.ext4 -L nixos /dev/vda1
   sudo mkswap -L swap /dev/vda2

2. Installing

   # activate swap device
   sudo swapon /dev/sda2
   
   # mount rootfs
   sudo mount /dev/disk/by-label/nixos /mnt
   
   # generate nixos config
   sudo nixos-generate-config --root /mnt
   
   # edit config file
   sudo vim /mnt/etc/nixos/configuration.nix
   
   # do the installation
   sudo nixos-install --no-root-password
   
   # reboot
   sudo reboot

Further readings

• NixOS Manual
• Nix Expression Language
• Creating guests with virt-install