nix-los/QUICKREF.md

Quick Reference

Common commands and patterns for your portable NixOS setup.

Deployment

Action	Command
Rebuild NixOS	sudo nixos-rebuild switch --flake .#laptop
Rebuild Home	home-manager switch --flake .#myusername@linux
Both	sudo nixos-rebuild switch --flake .#laptop + home-manager switch --flake .#myusername@linux
Test (no apply)	sudo nixos-rebuild test --flake .#laptop
Activate Home (test)	home-manager build --flake .#myusername@linux
Check validity	nix flake check
Show outputs	nix flake show
Update inputs	nix flake update
Update one input	nix flake update nixpkgs

Secrets

Action	Command
Generate age key	age-keygen -o -f ~/.config/sops/age/keys.txt
Get public key	age-keygen -y ~/.config/sops/age/keys.txt
Edit secrets	sops secrets/secrets.yaml
View secrets	sops -d secrets/secrets.yaml
Re-encrypt after .sops.yaml change	sops -e secrets/secrets.yaml > temp && mv temp secrets/secrets.yaml

Development

Action	Command
Enter dev shell	nix develop
Format Nix files	nixpkgs-fmt .
Check for syntax errors	nix flake check
Evaluate flake	nix eval .#
Get derivation path	nix derivation show .#youruser@linux

Utilities

Action	Command
List installed packages	nix-store -q --requisites /run/current-system
Find broken symlinks	nix store gc --print-roots
Clear old generations	sudo nix-collect-garbage -d
Clear user generations	nix-collect-garbage -d
Check disk usage	du -sh /nix

Files to Edit for Common Tasks

Task	File
Change hostname	hosts/laptop/default.nix (networking.hostName)
Add system packages	nixos/default.nix
Add user packages	home/default.nix
Change shell	nixos/modules/shell.nix (custom.shell.defaultShell)
Enable languages	hosts/laptop/default.nix (custom.development.languages)
Add Git config	home/modules/git.nix
Customize Neovim	home/modules/editor.nix
Add SSH keys	secrets/secrets.yaml (encrypted)
Change username	flake.nix, home/default.nix, nixos/modules/system.nix

Enable Features by Module

# Edit hosts/laptop/default.nix:

# Development tools
custom.development.enable = true;
custom.development.languages = [ "rust" "python" "nodejs" "go" "ruby" ];

# Shell setup
custom.shell.enable = true;
custom.shell.defaultShell = "zsh";  # or bash, fish

# System module
custom.system.enable = true;

Debugging

Problem	Solution
Can't find package	Check nixpkgs: nix search nixpkgs mycpackage
Module import error	Check imports in default.nix: nix flake check
Config won't build	Get detailed error: nix flake show 2>&1 | tail -50
Secrets not decrypting	Verify: sops -d secrets/secrets.yaml
Home-manager conflicts	Backup old config: mv ~/.bashrc ~/.bashrc.bak
Stuck rebuild	Kill and retry: sudo killall nixos-rebuild

Git Workflow

# After making changes:
git add -A
git commit -m "Update: description"
git push

# On another machine:
git pull
sudo nixos-rebuild switch --flake .#laptop

Multi-Machine Example

# Add new host
mkdir -p hosts/workstation
cp hosts/laptop/default.nix hosts/workstation/default.nix

# Add to flake.nix (copy laptop configuration block and update names)

# Deploy to new machine
sudo nixos-rebuild switch --flake .#workstation

One-Liner Installers

# Fresh NixOS to existing machine
git clone <repo> ~/nix-config && cd ~/nix-config && sudo nixos-rebuild switch --flake .#laptop

# Home manager on non-NixOS
curl https://nixos.org/channels/nixos-unstable/latest-nixos-*-linux/default.nix && \
  nix run home-manager -- init --switch --flake .#myusername@linux

# Update everything
nix flake update && sudo nixos-rebuild switch --flake .#laptop && \
  home-manager switch --flake .#myusername@linux

Tips

• ✅ Always commit flake.lock for reproducibility
• ✅ Use lib.mkDefault for overridable settings
• ✅ Keep secrets encrypted with sops
• ✅ Test with test before switch
• ✅ Use --build-on-remote for slower machines
• ✅ Check flake check before rebuilding
• ✅ Keep separate host configs for different machines
• ✅ Use home-manager generations to rollback if needed