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Nothing but Nix

Transform your GitHub Actions runner into a Nix ❄️ powerhouse by ruthlessly slashing pre-installed bloat.

GitHub Actions runners come with meager disk space for Nix - a mere ~20GB. Nothing but Nix brutally purges unnecessary software, giving you 65GB to 130GB for your Nix store! 💪

Usage 🔧

Add this action before installing Nix in your workflow:

jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      id-token: write
    steps:
      - uses: actions/checkout@v4
      - uses: wimpysworld/nothing-but-nix@main
      - name: Install Nix
        uses: DeterminateSystems/nix-installer-action@main
      - name: Run Nix
        run: |
          nix --version
          # Your Nix-powered steps here...

Requirements ️✔️

• Only supports official Ubuntu GitHub Actions runners
• Must run before Nix is installed

The Problem: Making Room for Nix to Thrive 🌱

Standard GitHub Actions runners are stuffed with "bloatware" you'll never use in a Nix workflow:

• 🌍 Web browsers. Lots of them. Gotta have 'em all!
• 🐳 Docker images consuming gigabytes of precious disk space
• 💻 Unnecessary language runtimes (.NET, Ruby, PHP, Java...)
• 📦 Package managers gathering digital dust
• 📚 Documentation no one will ever read

This bloat leaves only ~20GB for your Nix store - barely enough for serious Nix builds! 😞

The Solution: Nothing but Nix ️❄️

Nothing but Nix takes a scorched-earth approach to GitHub Actions runners and mercilessly reclaims disk space using a two-phase attack:

1. Initial Slash: Instantly creates a large /nix volume (~65GB) by claiming free space from /mnt
2. Background Rampage: While your workflow continues, we ruthlessly eliminate unnecessary software to expand your /nix volume up to ~130GB
   • Web browsers? Nope ⛔
   • Docker images? Gone 🗑️
   • Language runtimes? Obliterated 💥
   • Package managers? Annihilated 💣
   • Documentation? Vaporized ️👻

The file system purge is powered by rmz (from the Fast Unix Commands (FUC) project) - a high-performance alternative to rm that makes space reclamation blazing fast! ⚡

• Outperforms standard rm by an order of magnitude
• Parallel-processes deletions for maximum efficiency
• Reclaims disk space in seconds rather than minutes! ️⏱️

The end result? A GitHub Actions runner with 65GB to 130GB of Nix-ready space! 😁

Dynamic Volume Growth

Unlike other solutions, Nothing but Nix grows your /nix volume dynamically:

1. Initial Volume Creation (1-10 seconds): (depending on Hatchet Protocol)

   • Creates a loop device from free space on /mnt
   • Sets up a BTRFS filesystem in RAID0 configuration
   • Mounts with compression and performance tuning
   • Provides a 65GB /nix immediately, even before the purge begins

2. Background Expansion (30-180 seconds): (depending on Hatchet Protocol)

   • Executes purging operations
   • Monitors for newly freed space as bloat is eliminated
   • Dynamically adds an expansion disk to the /nix volume
   • Rebalances the filesystem to incorporate new space

The /nix volume automatically grows during workflow execution 🎩🪄

Choose Your Weapon: The Hatchet Protocol 🪓

Control the level of annihilation 💥 with the hatchet-protocol input:

- uses: wimpysworld/nothing-but-nix@main
  with:
    hatchet-protocol: 'cleave'  # Options: holster, carve, cleave (default), rampage

Protocol Comparison ⚖️

Protocol	/nix	Description	Purge apt	Purge docker	Purge snap	Purged file systems
Holster	~65GB	Keep the hatchet sheathed, use space from /mnt	No	No	No	None
Carve	~85GB	Craft and combine free space from / and /mnt	No	No	No	None
Cleave	~115GB	Make powerful, decisive cuts to large packages	Minimal	Yes	Yes	/opt and /usr/local
Rampage	~130GB	Relentless, brutal elimination of all bloat	Aggressive	Yes	Yes	Muahahaha! 🔥🌎

Choose wisely:

• Holster when you need the runner's tools to remain fully functional
• Carve to preserve functional runner tooling but claim all free space for Nix
• Cleave (default) for a good balance of space and functionality
• Rampage when you need maximum Nix space and don't care what breaks #nix-is-life

Witness The Carnage 🩸

By default, the purging process executes silently in the background while your workflow continues. But if you want to watch the slaughter in real-time:

- uses: wimpysworld/nothing-but-nix@main
  with:
    ️hatchet-protocol: 'cleave'
    witness-carnage: true  # Default: false

Customize Safe Havens 🛡️

Control how much space to spare from the Nix store land grab with custom safe haven sizes:

- uses: wimpysworld/nothing-but-nix@main
  with:
    ️hatchet-protocol: 'cleave'
    root-safe-haven: '3072'   # Reserve 3GB on the / filesystem
    mnt-safe-haven: '2048'    # Reserve 2GB on the /mnt filesystem

These safe havens define how much space (in MB) will be mercifully spared during space reclamation:

• Default root-safe-haven is 2048MB (2GB)
• Default mnt-safe-haven is 1024MB (1GB)

Increase these values if you need more breathing room on your filesystems, or decrease them to show no mercy! 😈

Grant User Ownership of /nix (Nix Permission Edict) 🧑‍⚖️

Some Nix installers or configurations expect the /nix directory to be writable by the current user. By default, /nix is owned by root. If you need user ownership (e.g., for certain Nix installer scripts that don't use sudo for all operations within /nix), you can enable the nix-permission-edict:

- uses: wimpysworld/nothing-but-nix@main
  with:
    nix-permission-edict: true  # Default: false

When nix-permission-edict is set to true, the action will run sudo chown -R "$(id --user)":"$(id --group)" /nix after mounting /nix.

Now go and build something amazing with all that glorious Nix store space! ❄️