# nix-git

This repository contains my NixOS configuration files with some guidance on how to use them.

See also:
- [TODO.md](./TODO.md)
- [NixOS.md](./NixOS.md)

## Table of Contents

<!-- TOC -->
* [nix-git](#nix-git)
  * [Table of Contents](#table-of-contents)
  * [NixOS installation](#nixos-installation)
    * [Graphical installation](#graphical-installation)
  * [Remote installation: disko and nixos-anywhere](#remote-installation-disko-and-nixos-anywhere)
  * [ARM device: SD image for the Raspberry Pi 3B+](#arm-device-sd-image-for-the-raspberry-pi-3b)
    * [ISO](#iso)
    * [Default configuration](#default-configuration)
    * [Apply modified configuration](#apply-modified-configuration)
  * [ARM device: Vanilla UEFI boot loader for the Raspberry Pi 3B+](#arm-device-vanilla-uefi-boot-loader-for-the-raspberry-pi-3b)
  * [Update, build and switch](#update-build-and-switch)
    * [Update](#update)
    * [Build and switch: Using Colmena](#build-and-switch-using-colmena)
    * [Build and switch: Manually](#build-and-switch-manually)
      * [Option I: Build new config and activate it:](#option-i-build-new-config-and-activate-it)
      * [Option II: Build new config and activate it during next boot:](#option-ii-build-new-config-and-activate-it-during-next-boot)
      * [Option III: Build config and view changes:](#option-iii-build-config-and-view-changes)
  * [niv: Dependency management](#niv-dependency-management)
    * [Add Home Manager with niv](#add-home-manager-with-niv)
    * [Add NUR with niv](#add-nur-with-niv)
  * [Colmena: Deployment and secret management](#colmena-deployment-and-secret-management)
  * [BTRFS swap file](#btrfs-swap-file)
  * [LUKS Parameters](#luks-parameters)
  * [Automount encrypted drive](#automount-encrypted-drive)
  * [Failed services](#failed-services)
  * [Garbage collection](#garbage-collection)
  * [References](#references)
<!-- TOC -->

## NixOS installation

### Graphical installation

For beginners, NixOS can be installed with a graphical installer.

Getting the ISO:

* There is no official torrent as they are not needed due to CDN.
* ISO and checksum are available here: https://nixos.org/download#nixos-iso
* There are unofficial torrents. If the checksum is compared with the one from the official website, these can be used as well: https://github.com/AnimMouse/NixOS-ISO-Torrents/releases

During installation:

* If the installation target is a SSD
  * Trim the whole disk to mark all cells as unused and restore its initial performance
  * `sudo blkdiscard -f /dev/nvmeXXX`
* Select manual partitioning:
  * One 512MB (or larger) Fat32 partition, mounted at `/boot`, "boot" flag enabled
  * Another partition (e.g. BTRFS) covering the rest of the drive, mounted at `/`, encryption enabled

## Remote installation: disko and nixos-anywhere

Install NixOS via SSH everywhere.

There is a separate repository for these steps. Its README can be found here: https://codeberg.org/privacy1st/nixos-anywhere-example/src/template/README.md

## ARM device: SD image for the Raspberry Pi 3B+

### ISO

If you are on an architecture other than aarch64, enable emulation: `boot.binfmt.emulatedSystems = [ "aarch64-linux" ];`.

An ISO for the Raspberry Pi 3B+ can then be built with:

```shell
# If on aarch64
#nix-build '<nixpkgs/nixos>' -A config.system.build.sdImage -I nixos-config=./iso-aarch64.nix
# If not on aarch64
nix-build '<nixpkgs/nixos>' -A config.system.build.sdImage -I nixos-config=./iso-aarch64.nix --argstr system aarch64-linux

ls result/sd-image/*.img
```

**Note** about cross compilation

Alternatively to emulating the aarch64 architecture we could also cross compile from e.g. x86 to it. However, this has one big drawback: The binary cache (https://cache.nixos.org/) won't be used. The reason for this is that packages built with cross compilation are (slightly) different from native built ones. Their checksums don't match.

### Default configuration

When the Raspberry Pi is booted, run `nixos-generate-config` to generate the default `configuration.nix` and `hardware-configuration.nix` files.

A slightly modified config can be found in [./hosts/pi3bplus/](./hosts/pi3bplus/)

### Apply modified configuration

The Rapberry Pi 3B+ has only 1GB RAM, which is not enough for `nixos-rebuild`. It is recommended to create and activate a SWAP file first: https://wiki.archlinux.org/title/swap#Swap_file_creation

```shell
nix-channel --list
#=> nixos https://nixos.org/channels/nixos-23.05
nix-channel --update nixos
```

```shell
passwd
```

```shell
nixos-rebuild boot
reboot
```

## ARM device: Vanilla UEFI boot loader for the Raspberry Pi 3B+

**TODO**: The EFI menu was working. But I got many squashfs errors when booting an USB stick with the NixOS installer.

* https://www.eisfunke.com/posts/2023/uefi-boot-on-raspberry-pi-3.html

Preparing a micro SD card with an UEFI boot loader:

```shell
nix-shell -p parted gptfdisk
```
```shell
sudo parted --script /dev/SDX -- \
	mklabel gpt \
	mkpart ESP fat32 2Mib 512MiB \
	set 1 esp on \
	mkpart primary 512MiB 100% \
	print

sudo wipefs --all /dev/SDX1
sudo wipefs --all /dev/SDX2

sudo mkfs.fat -F32 /dev/SDX1

sudo gdisk /dev/SDX
# r
# p
# h
# 1
# N
# 0c
# N
# N
# o
# w
# Y
```

In addition to the SD card, attach an USB stick with NixOS ARM (https://nixos.org/download.html#nixos-iso, https://hydra.nixos.org/job/nixos/release-23.05/nixos.iso_minimal.aarch64-linux, https://hydra.nixos.org/job/nixos/release-23.05/nixos.iso_minimal_new_kernel_no_zfs.aarch64-linux or https://hydra.nixos.org/job/nixos/trunk-combined/nixos.iso_minimal.aarch64-linux) to the Raspberry Pi.

```shell
sudo umount /dev/SDX
sudo dd if=nixos-minimal-XXX-aarch64-linux.iso of=/dev/SDX bs=4M conv=fsync
```

Then install NixOS the way you prefer, but don't touch/modify the partition table!

See https://nixos.wiki/wiki/NixOS_on_ARM/UEFI#Installing

## Update, build and switch

Local (yodaTux):

```shell
niv update && colmena build --on $(hostname) -v && colmena apply-local --sudo
```

Server:

```shell
niv update && colmena build --on @server -v && colmena apply --on @server switch
```

### Update

* Updating NixOS. https://superuser.com/a/1604695

Update channel and configuration:

```shell
sudo nix-channel --update && niv update
```

To apply the updates, continue with "Build and switch".

### Build and switch: Using Colmena

See section "Colmena: Deployment and secret management" to build and apply updates.

### Build and switch: Manually

* https://nixos.wiki/wiki/Nixos-rebuild
* https://discourse.nixos.org/t/how-to-get-this-pending-updates-notification-in-gnome/16344/3
* https://discourse.nixos.org/t/how-to-get-this-pending-updates-notification-in-gnome/16344/6

#### Option I: Build new config and activate it:

```shell
sudo nixos-rebuild -I nixos-config=hosts/$(hostname)/configuration.nix switch
```

To view changes, see section "Compare two versions of NixOS system profile".

#### Option II: Build new config and activate it during next boot:

```shell
sudo nixos-rebuild -I nixos-config=hosts/$(hostname)/configuration.nix boot
```

#### Option III: Build config and view changes:

```shell
# This leaves a symlink named `result` in the current directory.
sudo nixos-rebuild -I nixos-config=hosts/$(hostname)/configuration.nix build
nix --extra-experimental-features nix-command store diff-closures /run/current-system ./result
#=> ...
#=> linux: 6.1.47, 6.1.47-modules → 6.1.51, 6.1.51-modules, -11.8 KiB
```

Depending on if there are large kernel changes, either switch to it directly or wait until next boot:

```shell
sudo ./result/bin/switch-to-configuration switch
# or
sudo ./result/bin/switch-to-configuration boot
```

Note: The Perl script executed by both above commands _should_ create a new bootloader menu entry and mark it as default. However, if I remember correctly, the menu entry was once missing and the configuration change thus not permanent. This might need further testing. See also: https://nixos.wiki/wiki/Nixos-rebuild#Internals

## niv: Dependency management

* https://nix.dev/tutorials/first-steps/towards-reproducibility-pinning-nixpkgs#dependency-management-with-niv

niv:

> Easy dependency management for Nix projects.
>
> Nix is a very powerful tool for building code and setting up environments. niv complements it by making it easy to
> describe and update remote dependencies (URLs, GitHub repos, etc). It is a simple, practical alternative to Nix
> flakes.
>
> https://github.com/nmattia/niv

> Niv is an easy dependency management for Nix projects with package pinning.
>
> https://github.com/mikeroyal/NixOS-Guide

Initialize:

```shell
niv init
```

Change the tracking branch of nixpkgs from unstable to 23.05:

```shell
niv modify nixpkgs --branch nixos-23.05
```

Add nixpkgs unstable:

```shell
niv add NixOS/nixpkgs -n unstable -b nixpkgs-unstable
```

### Add Home Manager with niv

Home Manager:

> [Home Manager] allows declarative configuration of user specific (non-global) packages and dotfiles.
>
> To avoid breaking users' configurations, Home Manager is released in branches corresponding to NixOS releases (
> e.g. `release-23.05`).
>
> Home Manager provides both the channel-based setup and the flake-based one.
>
> https://github.com/nix-community/home-manager

Check your channel:

```shell
sudo nix-channel --list
#=> nixos https://nixos.org/channels/nixos-23.05
```

Use the corresponding branch:

```shell
niv add nix-community/home-manager -n home-manager -b release-23.05
```

### Add NUR with niv

> The Nix User Repository (NUR) is community-driven meta repository for Nix packages.
> 
> ... packages are built from source and are not reviewed by any Nixpkgs member.
> 
> https://github.com/nix-community/NUR

```shell
niv add nix-community/NUR -n NUR
```

## Colmena: Deployment and secret management

* https://github.com/zhaofengli/colmena#colmena

> Colmena is a simple, stateless NixOS deployment tool modeled after NixOps and morph, written in Rust.

Alternative: Deployment with Morph: https://xeiaso.net/blog/morph-setup-2021-04-25

Configuration is done inside [hive.nix](hive.nix).

Build config:

```shell
colmena build -v
```

Apply to all non-local nodes:

```shell
colmena apply --on @server switch
#colmena apply --on @server boot

#colmena apply --on @yodaTab switch
#colmena apply --on @yodaTab boot
```

Apply to local node:

```shell
colmena apply-local --sudo switch
#colmena apply-local --sudo boot
```

Filtering:
- You can filter hosts by tags with `--on @tag-a,@tag-b`.
- You can use globs in tag matching as well: `colmena apply --on '@infra-*'`

## BTRFS swap file

* Detailed instructions: https://nixos.wiki/wiki/Btrfs#Swap_file
* https://wiki.archlinux.org/title/btrfs#Swap_file

Summary:

* Create subvolume `@swap` directly below top-level subvolume.
* Mount at `/swap`
* Create swapfile: `sudo btrfs filesystem mkswapfile --size 8g --uuid clear /swap/swapfile`
* Regenerate hardware-configuration: `sudo nixos-generate-config --dir hosts/$(hostname)`
* Add `swapDevices = [ { device = "/swap/swapfile"; } ];` to hardware configuration and run `nixos-rebuild switch` (see above).

## LUKS Parameters

**Warning**: NixOS has a hardcoded timeout of 10 seconds when opening encrypted drives during boot. Please choose `--iter-time` <= `5000`.

* https://github.com/NixOS/nixpkgs/blob/ed2ccd4d1748e52d5d28c440d5be4b25a4f21c08/nixos/modules/system/boot/luksroot.nix#L498
* https://github.com/NixOS/nixpkgs/blob/ed2ccd4d1748e52d5d28c440d5be4b25a4f21c08/nixos/modules/system/boot/luksroot.nix#L30
* https://github.com/NixOS/nixpkgs/blob/ed2ccd4d1748e52d5d28c440d5be4b25a4f21c08/nixos/modules/system/boot/luksroot.nix#L36C7-L36C7

## Automount encrypted drive

~~* Generate and add keyfile to LUKS device~~
* Use the same password for all attached LUKS devices to be only prompted once while booting
  * Discussion: https://discourse.nixos.org/t/how-to-unlock-some-luks-devices-with-a-keyfile-on-a-first-luks-device/18949/11
  * Related NixOS config option: https://github.com/NixOS/nixpkgs/blob/ed2ccd4d1748e52d5d28c440d5be4b25a4f21c08/nixos/modules/system/boot/luksroot.nix#L570-L584
* luksOpen and mount drive, e.g. to `/mnt/data1`
* Re-generate hardware configuration:

```shell
sudo nixos-generate-config --dir hosts/$(hostname)
```

* If it is an SSD, enable `boot.initrd.luks.devices.<name>.allowDiscards`

## Failed services

If there are e.g. file conflicts due to preexisting dotfiles, the Home Manager user service might fail. To list all failed services, run:

```shell
systemctl --failed
```

## Garbage collection

* https://nixos.org/manual/nix/stable/package-management/garbage-collection.html
* https://discourse.nixos.org/t/why-doesnt-nix-collect-garbage-remove-old-generations-from-efi-menu/17592/4

This is automated in [base.nix](modules/base.nix) with the `nix.gc` option.

Run manually for all profiles:

```shell
sudo nix-collect-garbage --delete-older-than 14d
```

Remove leftover EFI entries of removed generations:

```shell
sudo /run/current-system/bin/switch-to-configuration boot
```