installing nixos on oracle free tier

don't care about the writeup? skip to the installation instructions

always free

at the time of writing this oracle cloud offers a suprisingly generous always free tier. you get:

• AMD: 2 VMs with 1/8 OCPU and 1GB RAM each
• Arm (Ampere A1): 24GB RAM and 4 OCPU, which can be split across 1-4 VMs

in total that is 26GB of RAM and 4.25 OCPUs - completely free! (assuming you can get a spot. as you might expect, this offering is extremely popular.)

that's awesome - what's the catch?

there's no real catch - but one major limitation is that nixos isn't available as a default image.

not to worry though - i've written a few simple scripts that lets you install nixos from just about any other os that has a bash shell.

installation

step 1

ssh into your vm and run the following command:

curl -sSL https://salad.newty.dev/guides/oracle/kexec.sh | sudo bash

this will download and run a script that installs a nixos installation environment matching your vm's architecture, then reboots into it using kexec.

step 2

ssh back into your machine, this time as the root user. run the following commands:

curl -sSL https://salad.newty.dev/guides/oracle/install.sh -o install.sh
bash install.sh "<ssh key>" "<swap size>"

replace <ssh key> with your public ssh key and <swap size> with the swap size you'd like (e.g. 1G or 512M).

this script will:

• partition and format the disk
• configure and install a minimal nixos system
• setup networking and ssh access
• enable your specified ssh key
• reboot into your fresh nixos installation

conclusion

once you've followed the steps above, you'll have a fully functional nixos installation running on oracle cloud.

from here, you can configure it just like any other nixos system.

appendix: script contents

just for transparency, here are all of the files installed to your virtual machine when running the scripts:

kexec.sh

#!/bin/bash

ARCH=$(uname -m)

echo "Detected architecture: $ARCH"

case $ARCH in
    aarch64)
        INSTALLER="https://github.com/nix-community/nixos-images/releases/download/nixos-unstable/nixos-kexec-installer-noninteractive-aarch64-linux.tar.gz"
        ;;
    x86_64)
        INSTALLER="https://github.com/nix-community/nixos-images/releases/download/nixos-unstable/nixos-kexec-installer-noninteractive-x86_64-linux.tar.gz"
        ;;
esac

sudo bash -c "
    curl -L '$INSTALLER' | tar -xzf- -C /root
    /root/kexec/run
"

install.sh

#!/bin/bash

# check if ssh key and swap size are provided
if [ $# -lt 2 ]; then
    echo "Usage: $0 '<ssh-public-key>' '<swap-size>'"
    echo "Example: $0 'ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGm... user@host' '1G'"
    echo "Swap size examples: 1G, 2G, 512M"
    exit 1
fi

SSH_KEY="$1"
SWAP_SIZE="$2"

# --- partition ---

# see: https://mdleom.com/blog/2021/03/09/nixos-oracle/
# uses 1G swap by default
fdisk /dev/sda << EOF
g
n
1

+512M
n
2

-${SWAP_SIZE}
n
3


t
1
uefi
p
w
EOF

fdisk -l /dev/sda

# --- format ---
mkfs.fat -F 32 -n boot /dev/sda1
mkfs.ext4 -L nixos /dev/sda2
mkswap -L swap /dev/sda3

# --- mount ---
mkdir -p /mnt
mount /dev/disk/by-label/nixos /mnt
mkdir -p /mnt/boot
mount /dev/disk/by-label/boot /mnt/boot
swapon /dev/sda3

# --- configuration ---
nix-channel --add https://nixos.org/channels/nixos-unstable nixpkgs
nix-channel --update

nixos-generate-config --root /mnt
curl -L https://salad.newty.dev/guides/oracle/configuration.nix -o /mnt/etc/nixos/configuration.nix
sed -i "s|<ssh key>|$SSH_KEY|g" /mnt/etc/nixos/configuration.nix

# --- installation ---
nixos-install
reboot

configuration.nix

{
  pkgs,
  ...
}:

{
  imports = [
    ./hardware-configuration.nix
  ];

  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  networking.hostName = "nixos";
  networking.networkmanager.enable = true;

  time.timeZone = "Europe/London";

  users.users.newt = {
    isNormalUser = true;
    extraGroups = [ "wheel" ];
  };

  environment.systemPackages = with pkgs; [
    curl
    git
  ];

  services.openssh.enable = true;
  users.users.root.openssh.authorizedKeys.keys = [
    "<ssh key>"
  ];

  system.stateVersion = "25.11";
}