Minecraft Mod Management for NixOS (Packwiz)

Overview

This skill helps manage Minecraft server mods in the NixOS configuration using packwiz as the source of truth. The minecraft-server.nix module automatically parses packwiz .pw.toml files to build the server modpack.

File Locations

•Server Module: /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft/minecraft-server.nix
•
Packwiz Modpack: /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft/modpack/
- •pack.toml - Modpack metadata (Minecraft version, Fabric version)
- •index.toml - Auto-generated index of all mods (managed by packwiz)
- •mods/*.pw.toml - Individual mod metadata files with URLs and hashes
•Update Script: /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft/packwiz-update.sh
•README: /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft/README.md

How It Works

Architecture

The minecraft-server.nix module uses a functional approach to build the modpack:

•Parsing .pw.toml files: The parseModToml function reads each mod's .pw.toml file
•Server-side filtering: Only includes mods where side = "both" or side = "server"
•Hash verification: Supports sha256, sha512, and sha1 hash formats
•Automatic building: Creates a linkFarmFromDrvs with all server mods

nix

# Key components from minecraft-server.nix
parseModToml = tomlFile: let
  tomlContent = builtins.fromTOML (builtins.readFile tomlFile);
  isServerMod = tomlContent.side == "both" || tomlContent.side == "server";
  # ... hash handling ...
in
  if isServerMod
  then pkgs.fetchurl { url = ...; sha512 = ...; name = ...; }
  else null;

# All server mods automatically loaded
serverMods = builtins.filter (mod: mod != null) (
  map (file: parseModToml (modpackPath + "/mods/${file}"))
  (builtins.filter (file: lib.hasSuffix ".pw.toml" file) modFiles)
);

Packwiz Workflow

Packwiz manages mod metadata in .pw.toml files. Each file contains:

•Download URL (typically Modrinth CDN)
•Filename
•Hash (for verification)
•Side (client, server, or both)
•Update information

Common Operations

Prerequisites

All packwiz commands should be run in the modpack directory:

bash

cd /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft/modpack

You can run packwiz via nix-shell:

bash

nix-shell -p packwiz --run "packwiz <command>"
# or enter a shell
nix-shell -p packwiz

Adding a Mod

bash

# Add from Modrinth (recommended)
packwiz modrinth add <mod-slug>

# Example: Add Sodium
packwiz modrinth add sodium

# Non-interactive mode (auto-accept dependencies)
packwiz modrinth add -y sodium

# Add from CurseForge
packwiz curseforge add <mod-name>

Packwiz will:

•Download mod metadata
•Create a .pw.toml file in mods/
•Update index.toml automatically
•Prompt for required dependencies (unless using -y)

Removing a Mod

bash

packwiz remove <mod-name>

# Example
packwiz remove sodium

Updating Mods

Update all mods:

bash

# Using packwiz directly
packwiz update --all

# Using the update script (recommended - has better progress tracking)
cd /home/curtbushko/workspace/github.com/curtbushko/nixos-config/modules/nixos/services/minecraft
./packwiz-update.sh

Update a specific mod:

bash

packwiz update <mod-name>

The packwiz-update.sh script:

•Updates all mods with progress tracking
•Shows which mods updated successfully
•Identifies mods stuck on older Minecraft versions
•Includes delay between updates to avoid rate limiting

•Configurable via environment variables:

bash

DELAY_SECONDS=3 ./packwiz-update.sh
DRY_RUN=true ./packwiz-update.sh  # See what would happen

Listing Mods

bash

# List all mods
packwiz list

# Count mods
packwiz list | wc -l

Refreshing Index

After manually editing .pw.toml files:

bash

packwiz refresh

Changing Minecraft Version

To upgrade to a new Minecraft version (e.g., 1.20.1 → 1.21.1):

1. Update pack.toml:

bash

cd modpack
nano pack.toml
# Change:
# [versions]
# minecraft = "1.21.1"

2. Update all mods for new version:

bash

# Refresh to pick up new Minecraft version
packwiz refresh

# Update all mods (they'll fetch versions for new MC version)
cd ..
./packwiz-update.sh

3. Update server package in minecraft-server.nix:

nix

# Change from:
package = pkgs.fabricServers.fabric-1_20_1;
# To:
package = pkgs.fabricServers.fabric-1_21_1;
# Note: Use underscores, not dots!

4. Check for mods without 1.21.1 versions: The packwiz-update.sh script will report mods stuck on older versions. You may need to:

•Find alternative mods
•Wait for mod updates
•Use compatibility layers (e.g., Sinytra Connector for NeoForge mods)

Understanding .pw.toml Files

Example mod file (mods/sodium.pw.toml):

toml

name = "Sodium"
filename = "sodium-fabric-0.6.5+mc1.21.1.jar"
side = "both"

[download]
url = "https://cdn.modrinth.com/data/AANobbMI/versions/abc123/sodium-fabric-0.6.5+mc1.21.1.jar"
hash-format = "sha512"
hash = "abc123..."

[update]
[update.modrinth]
mod-id = "AANobbMI"
version = "abc123"

Key fields:

•side - Determines if mod loads on server: "both", "server", or "client"
•download.url - Direct download URL (usually Modrinth CDN)
•download.hash-format - Hash type (sha256, sha512, or sha1)
•download.hash - Hash for verification
•update.modrinth.mod-id - Used by packwiz to check for updates

Client Modpack

The packwiz modpack can be shared with clients:

Option 1: Packwiz Installer (Recommended) Clients run packwiz-installer in their .minecraft directory to auto-download all client-compatible mods.

Option 2: Export to modpack format

bash

cd modpack
packwiz modrinth export     # Creates .mrpack file
packwiz curseforge export   # Creates .zip for CurseForge

Troubleshooting

Mod not found for Minecraft version

Some mods may not support the target version yet:

bash

# Search for alternatives
packwiz modrinth search <name>

# Check mod page manually
# https://modrinth.com/mod/<slug>

Dependencies

Packwiz prompts for dependencies automatically:

code

Mod X requires dependency Y. Install? [Y/n]

Use -y flag to auto-accept: packwiz modrinth add -y <mod>

Side Configuration

If a mod should be server-only but packwiz marks it as "both":

•Edit the .pw.toml file manually
•Change side = "both" to side = "server"
•Run packwiz refresh

NixOS Build Integration

When you rebuild NixOS:

•The module reads all .pw.toml files in modpack/mods/
•Filters for server-compatible mods (side = "both" or side = "server")
•Downloads and verifies each mod using hashes
•Creates symlink farm for the Minecraft server

No manual hash management needed - packwiz handles all hashes automatically!

Resource Packs and Datapacks

These are still manually configured in minecraft-server.nix:

Resource packs (lines 54-115):

nix

resourcepacks = pkgs.linkFarmFromDrvs "resourcepacks" [
  (pkgs.fetchurl { url = "..."; sha512 = "..."; name = "..."; })
];

Datapacks (lines 118-125):

nix

datapacks = pkgs.linkFarmFromDrvs "datapacks" [
  (pkgs.fetchurl { url = "..."; sha512 = "..."; name = "..."; })
];

These can be found on Modrinth but aren't managed by packwiz in this configuration.

Critical Checklist

When working with Minecraft server mods:

•✓ Always work in the modpack/ directory for packwiz commands
•✓ Use packwiz modrinth add to add mods (not manual editing)
•✓ Use packwiz-update.sh for bulk updates with progress tracking
•✓ Check side field in .pw.toml - client-only mods won't load on server
•✓ Update pack.toml Minecraft version before migrating versions
•✓ Update server package in minecraft-server.nix to match Minecraft version
•✓ Let packwiz handle all dependencies automatically
•✓ Don't manually edit index.toml (auto-generated)
•✓ NixOS rebuild will automatically pick up packwiz changes

Quick Reference

bash

# Navigate to modpack
cd /home/curtbushko/.../nixos-config/modules/nixos/services/minecraft/modpack

# Add mod
nix-shell -p packwiz --run "packwiz modrinth add <slug>"

# Remove mod
nix-shell -p packwiz --run "packwiz remove <name>"

# Update all mods
cd .. && ./packwiz-update.sh

# List mods
nix-shell -p packwiz --run "packwiz list"

# Change Minecraft version
# 1. Edit modpack/pack.toml
# 2. Run ./packwiz-update.sh
# 3. Update minecraft-server.nix server package

Minecraft Mods

Minecraft Mod Management for NixOS (Packwiz)

Overview

File Locations

How It Works

Architecture

Packwiz Workflow

Common Operations

Prerequisites

Adding a Mod

Removing a Mod

Updating Mods

Listing Mods

Refreshing Index

Changing Minecraft Version

Understanding .pw.toml Files

Client Modpack

Troubleshooting

Mod not found for Minecraft version

Dependencies

Side Configuration

NixOS Build Integration

Resource Packs and Datapacks

Critical Checklist

Quick Reference

Resources