Install NixOS on Linode

This tutorial is written for people who want to run NixOS on a Linode instance. We assume you are using the KVM hypervisor instead of the older hypervisor, Xen.

In this tutorial, we will show you how to set up NixOS on Linode by setting up disk, installing Nix onto the rescue OS, and use Nix to install NixOS onto your disks.

Create a Linode Instance

Linode uncreatively calls each virtual server a Linode itself. We'll be calling them a Linode instance. Create one of whichever size you prefer and wherever you prefer to locate it. Linode will direct you to the Dashboard tab of the Linode Manager.

Setup Disks

Create Disk Images

On the Dashboard tab, there is an option Create a new disk. You will need to create a single disk.

• label: nixos
• type: ext4
• size: Maximum

Note: The label is arbitrary.

Boot into Finnix

Now that you have the disks created, it's time to boot the Linode instance. Go to the Rescue tab in the Linode Manager, and select Reboot into Rescue Mode, which uses Finnix as an OS.

Now that it's started, connect to it via SSH. In the Remote Access tab of the Linode Manager, there's either Lish via Ajaxterm or Lish via SSH. The SSH option is much more pleasant to use since Ajaxterm disconnects after a couple minutes of idle. Pick one, and connect. If it asks for a password, give your Linode password.

Once in, it'll say Welcome to Finnix! amongst other things.

Note: The Lish shell does not let you scroll back and if you write or paste a line that is longer than the line length, it'll write over the beginning of your line visually. Even if you ssh into it through a terminal that doesn't have these issues, you will get them. Just be glad you only need to use Lish to set up NixOS, not use it.

Repartitioning

With this single disk, we are going to repartition it into four different disks: A disk for grub, a boot disk, a swap disk, and the actual nixos disk. To do this, we will use gdisk. Without a swap disk, the actual installation with run out of memory.

gdisk /dev/sda

To create new partitions, type n and follow the instructions. The following table shows the values you need. When finished, write your changes and exit with w. This will create four devices, /dev/sda1 through /dev/sda4.

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048            4095   1024.0 KiB  EF02A BIOS boot partition
   2            4096         1028095   500.0 MiB   8300  Linux filesystem
   3         1028096         3125247   1024.0 MiB  8200  Linux swap
   4         3125248        50331614B 22.5 GiB    8300  Linux filesystem

A: Note that the BIOS boot partition with `EF02` is mandatory because the direct disk boot approach requires that you set aside this sector for your BIOS. B: The end sector for the final partition is dependent upon the size of the Linode you are creating. This sector is the final sector on the smallest available Linode instance.

After creating, we now need to format them, since gdisk does not actually format them.

mkfs.ext4 -L nixos /dev/sda4
mkfs.ext4 -L boot /dev/sda2
mkswap -L swap /dev/sda3

Mounting

The devices now need to be mounted, and swap turned on.

mount /dev/sda4 /mnt
mkdir /mnt/boot
mount /dev/sda2 /mnt/boot
swapon /dev/sda3

Install Nix

We are going to install Nix into your Rescue System and use that to install NixOS onto your nixos disk. Nix can be used without NixOS, and that is what we are doing here - installing Nix so that it can install NixOS which will come with its own Nix.

Create Temp User

Installing Nix as root does not work. Create a new user so that you can install Nix. This new user will not exist once the process is finished. We will also need a group nixbld and a set of users in that group.

adduser nix

You will need to set a password. It will never be asked for, but you need to have one anyways.

groupadd -r nixbld
for n in $(seq 1 10); do useradd -c "Nix build user $n" \
    -d /var/empty -g nixbld -G nixbld -M -N -r -s "$(which nologin)" \
    nixbld$n; done

Note: If you paste this all in at once, only the adduser command will execute. Do the addusercommand separately from the other commands.

Download and Build

Now, to install Nix itself, we need to set up an environment to install in and then download and run the Nix installer as the nix user. Now do the Nix install:

update-ca-certificates
mkdir /nix
chown -R nix /nix
su - nix
bash <(curl https://nixos.org/nix/install)
exit

Note: Yes, we are piping curl into bash. You'll have to trust that the nixos.org website isn't hacked.

Now that Nix is installed, the rest must be done as root, which the exit puts you back into. From here on, you do not need the nix user at all.

Create a Nix Profile

Next up, create a Nix profile for the root user, remove the default nixpkgs channel, and add the nixos channel.

. ~nix/.nix-profile/etc/profile.d/nix.sh 
nix-channel --remove nixpkgs
nix-channel --add http://nixos.org/channels/nixos-17.09 nixos
nix-channel --update

Optional: Install vim for editing (>= 2048mb linode)

If you want to use vim to edit text instead of nano, install it.

nix-env -i vim_configurable

Note: Because the size of your linode determines the size of the / ramdisk, only a linode larger or equal to 2048 will fit vim.

Install nixos-install packages

Next up, let's actually get the NixOS installation file. Create a configuration file for Nix that is mostly empty, set some shell variables, and then install some packages.

cat <<EOF > /root/configuration.nix
{ fileSystems."/" = {};
  boot.loader.grub.enable = false;
} 
EOF
export NIX_PATH=nixpkgs=/root/.nix-defexpr/channels/nixos:nixos=/root/.nix-defexpr/channels/nixos/nixos
export NIXOS_CONFIG=/root/configuration.nix
nix-env -i -A config.system.build.nixos-install \
           -A config.system.build.nixos-option \
           -A config.system.build.nixos-generate-config \
           -f "<nixos>"

Configure NixOS

Now that you have the NixOS installation packages installed, it's time to build the configuration for your system. If you already have a configuration file that you saved somewhere else, you can put it in /mnt/etc/nixos/configuration.nix directly. If you do so, jump down to Install NixOS!

Generate configuration files

These will generate your configuration files in /mnt/etc/nixos/.

export NIX_PATH=nixpkgs=/root/.nix-defexpr/channels/nixos:nixos=/root/.nix-defexpr/channels/nixos/nixos
nixos-generate-config --root /mnt

Fix hardware-configuration.nix

The hardware scan fails to find the correct setup for us. As such, replace the hardware-configuration.nix file with the following:

imports = 
  [ <nixpkgs/nixos/modules/profiles/qemu-guest.nix>
  ];

Note: The only part that changes is the thing in <> brackets.

Fix Kernel Modules Setting

Make sure in your hardware_configuration.nix, you have the following line. You can add other kernel modules if you want.

boot.initrd.availableKernelModules = [ "virtio_net" "virtio_pci" "virtio_blk" "virtio_scsi" "9p" "9pnet_virtio" "ata_piix" "virtio_pci" ];

The NixOS 2014.12 qemu-guest hardware module is missing the virtio_scsi module.

Make sure GRUB and Linux use serial console for lish

As lish requires output to a serial console, some further changes are required in configuration.nix to ensure that you can use lish to administer nixos.

boot.kernelParams = [ "console=ttyS0" ];
boot.loader.grub.extraConfig = "serial; terminal_input serial; terminal_output serial";

Without the first line, you will never see the Linux kernel load in the lish console, and without the second line you will never see the GRUB menu.

Tell GRUB the boot device

In configuration.nix, uncomment the following line:

boot.loader.grub.device = "/dev/sda";

Longview Service (Optional) To enable Longview metrics:

services.longview.enable = true;
services.longview.apiKey = "01234567-89AB-CDEF-0123456789ABCDEF";

The apiKey value can be found in Longview settings. The Longview service is not yet available in the stable channel.

Other Changes

Do other changes. Get your users set up as you want them. Get databases and what not set up. Set up your ports. Anything you care about really.

Install NixOS!

Whoo! Everything's ready now. Just install nixos with its very own command.

unset NIXOS_CONFIG
nixos-install

Set Root Password

You should set the root password here. If you forget, you can use Linode's "Reset Root Password" option in the Rescue tab after finishing the install.

nixos-install --chroot
(chroot)$ passwd
Enter new UNIX password: ...
                         ...
                         ...
(chroot)$ exit

Shut Down Finnix

The installation is finished. So, Shut down the linode. The last steps before booting the system is creating a configuration profile in the Linode Manager:

• Boot Settings
  • Kernel: Direct Disk
• Block Device Assignment
  • /dev/sda: nixos (or whatever you named it at the beginning)
  • root device: /dev/sda

Change other configuration options to your preference.

Here's is a sample configuration options: