• What Is Nix?
  • The Operating System
  • The Language
  • The Package Manager
• Update Commands
• Rollback Command
• Fresh Install
  • Mismatched-Hash
  • Post-Setup
• Lost Bootloader
• Useful NixOS Resources:

Nix refers to the holy trinity: An operating system, a programming language, and a package manager.

• NixOS is a Linux distribution that's configured directly from these dotfiles, and can be rolled back upon a system breaking config change. This allows fearless tinkering!
• NixOS isn't FHS compliant, and cannot execute random binaries. However, there are workarounds for these two issues.

• NixLang is a functional programming language which means it's pure and immutable. There is no state in a functional programming language.

• By far the best of the three is Nix the package manager. It allows declarative, rather than imperative, package management. This provides repoducibility among many systems, including even MacOS!
• An interesting (although not very useful for many) result that comes from this declarative structure is the fact that a system configured in this declarative way can survive bit rot.
• Nix shells allow you to temporarily download packages for one time uses. The package manager will then garbage collect (at your discretion) and remove these packages. No longer do you have to worry about bloat accumulating from packages you forgot to remove!

• nix flake update
• sudo nixos-rebuild switch --flake .#default
• home-manager switch --flake .#axelcool1234

• sudo nixos-rebuild switch --flake .#default --rollback

Firstly... DON'T PANIC! This will be an easy transition - even if we only have the terminal (I'm assuming we start in the base home directory).

1. Execute sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos
2. Execute sudo nix-channel --list and ensure you only have the unstable branch as a channel. Call sudo nix-channel --remove [name] if that's not the case.
3. Execute sudo nix-channel --add https://github.com/nix-community/home-manager/archive/master.tar.gz home-manager
4. Execute sudo nix-channel --update

• This website has more information about installing home-manager (you shouldn't need this, but just in case!): https://nix-community.github.io/home-manager/index.xhtml#sec-install-standalone
• To ensure it has been installed correctly, try "man home-configuration.nix" - this might only work after step 5.

5. Execute nix-shell -p home-manager git
6. Clone this repository - git clone https://github.com/axelcool1234/.dotfiles.git
7. Execute cp /etc/nixos/hardware-configuration.nix .dotfiles/hosts/Legion-Laptop/hardware-configuration.nix
8. Execute cd .dotfiles
9. Execute nix flake update (you may need to temporarily enable experimental features for the command)
10. Execute sudo nixos-rebuild switch --flake .#default
11. Execute home-manager switch --flake .#axelcool1234

If home-manager fails to install due to a mismatch in a hash, that means we need to update that hash. If you don't know where the mismatched hash is, I recommend:

1. Execute nix-shell -p ripgrep
2. Execute rg and then part of the name of the derivation with the mismatched hash. You should be able to find where it's located.
3. Change the sha256 of the derivation with the sha256 the home-manager error outputted.
4. Try to execute home-manager switch --flake .#axelcool1234 again.

Once this is all done, we can execute reboot and get into our system. It should be just as how you remembered it! Remember to commit and push these .dotfiles, since you called nix flake update! You may need to do the post-setup steps to be able to properly commit and push these changes.

We need to make sure our github is configured with an SSH key so we can actually develop! Arguably, this step should be set up using something like sops Nix. At some point I'll have to learn how to use that - or some other secret management system for Nix.

1. Execute ssh-keygen
2. Execute cat and wherever the result of the ssh-keygen was stored. We want the .pub file to be outputted, so we can copy it.
3. Paste the copied SSH key on github by going to Settings -> "SSH and GPG Keys" -> "New SSH Key" and then save the new SSH key
4. Execute cd .dotfiles
5. Execute git remote set-url origin [email protected]:axelcool1234/.dotfiles.git
6. Execute git fetch

You can now commit and push changes to the .dotfiles to GitHub!

Has your bootloader been wiped? Try this:

1. Boot up a live installation USB (as long as it's Linux this solution should work)
2. Execute lsblk -o +LABEL and identify your Linux root partition (the one with the most space) and the boot partition (should be something like 512 MB)
3. Execute sudo mount /dev/[linux root partition] /mnt
4. Execute sudo mount /dev/[linux boot partition] /mnt/boot
5. cd to /mnt
6. Execute cd /home/axelcool1234/.dotfiles
7. Execute sudo nixos-install --flake .#default

Your bootloader should've been reinstalled. Now, when you reboot, GRUB (or whatever bootloader being used at the time) should start up. Make sure to execute nixos-switch once you've booted into NixOS so that GRUB can be reconfigured.

For more information, I learned how to do this from this discussion.

• https://mynixos.com/
  • Great for browsing options from NixOS and Home-manager
• https://search.nixos.org/packages
  • Great for searching for available packages
• https://noogle.dev/
  • Great for searching the NixLang library