NixOS Installation Guide on a Distant VPS

This guide explains how to install NixOS on a Contabo VPS using BTRFS subvolumes and a proper partition scheme.

Although this guide can be used on any distant machine, it heavily supposes you have access to a Rescue System, i.e. that you can boot an OS on your VPS without using its main drive (e.g. /dev/sda in the current template).

Important Prerequisites

CRITICAL: You MUST start your Contabo VPS in Rescue Mode (available in Contabo's control panel) before beginning this installation. This is necessary because we need to completely reformat /dev/sda, which is impossible while the system is running from it.

It's not possible on your current cloud provider? See alternative methods:

• nixos-anywhere,
• nixos-infect.

Partition Scheme

The installation uses the following partition layout:

• /dev/sda1 (1GB, ext4): Boot partition
• /dev/sda2 (Remaining space, BTRFS): Main system partition with subvolumes:
  • @: Root filesystem
  • @home: User home directories
  • @nix: Nix store
  • @var: Variable data

BTRFS subvolumes provide better snapshot management and more flexible space allocation.

Installation Steps

1. Initial Setup:

   • Boot into Rescue System from Contabo control panel
   • Download and execute the installation script
   • The script will:
     • Create a temporary Nix store
     • Set up build users
     • Install the Nix package manager

2. Disk Partitioning:

   • Completely wipes /dev/sda
   • Creates an MBR partition table
   • Sets up boot and main system partitions
   • Formats partitions with ext4 and BTRFS

3. BTRFS Configuration:

   • Creates optimized subvolumes
   • Mounts all partitions with appropriate options
   • Enables compression (zstd:6)
   • Configures BTRFS-specific optimizations

4. NixOS Installation:

   • Generates initial configuration
   • Installs base system
   • Configures GRUB bootloader

Key Configuration Choices

The installation includes several optimized choices:

• BTRFS Features:

  • Compression enabled (zstd:6)
  • Async discard for better SSD performance
  • Optimized mount options for each subvolume

• Memory Management:

  • /tmp mounted as tmpfs with 4GB size limit
  • Secure tmpfs permissions (mode 1777)
  • zramswap configured for efficient memory compression:
    • zstd compression algorithm
    • Uses 50% of system RAM
    • Provides additional swap space without disk I/O

• System Configuration:

  • GRUB bootloader with OS prober
  • SSH enabled with root login (change this after install!)
  • Firewall configured for SSH access
  • Nix flakes enabled
  • Basic system packages (vim, git)
  • /tmp mounted as tmpfs (4GB, mode 1777)
  • zramswap enabled (zstd compression, 50% of RAM)

Usage

1. Clone this repository locally, and review the configuration.nix and hardware-configuration.nix
2. Boot your VPS into Rescue Mode
3. Execute the installation script:

   curl -O https://raw.githubusercontent.com/clementpoiret/nixos-vps-install-script/main/install.sh
   chmod +x install.sh
   ./install.sh

4. The script will open vi to edit configuration.nix and hardware-configuration.nix. Please find my current minimal config here: configuration.nix, hardware-configuration.nix.
5. Once both files are edited, the script runs nixos-install.

Post-Installation

After installation:

1. Reboot into your new NixOS system
2. Add the nixos-unstable channel: nix-channel --add https://nixos.org/channels/nixos-unstable nixos nix-channel --update
3. Change root password
4. Configure additional users
5. Disable root SSH access
6. Configure your timezone (default is UTC)

Security Notes

The default configuration enables root SSH access to allow initial setup. Make sure to:

• Change the root password immediately
• Create regular user accounts
• Disable root SSH access
• Configure SSH keys
• Review and adjust firewall rules

Contributing

Feel free to submit issues and enhancement requests!