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NixOS

NixOS installation

Graphical installation

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

Getting the ISO:

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:

# 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/

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

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

passwd

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.

Preparing a micro SD card with an UEFI boot loader:

nix-shell -p parted gptfdisk

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.

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):

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

Server:

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

Update

Update channel and configuration:

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

Option I: Build new config and activate it:

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:

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

Option III: Build config and view changes:

# 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:

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

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:

niv init

Change the tracking branch of nixpkgs from unstable to 23.05:

niv modify nixpkgs --branch nixos-23.05

Add nixpkgs unstable:

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:

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

Use the corresponding branch:

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

niv add nix-community/NUR -n NUR

Colmena: Deployment and secret management

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.

Build config:

colmena build -v

Apply to all non-local nodes:

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

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

Apply to local node:

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

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.

Automount encrypted drive

* Generate and add keyfile to LUKS device

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:

systemctl --failed

Garbage collection

This is automated in base.nix with the nix.gc option.

Run manually for all profiles:

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

Remove leftover EFI entries of removed generations:

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

Run AppImages

# Note how your shell prefix changes.
nix-shell -p appimage-run

# Inside the shell, you can run an AppImage:
appimage-run ~/Downloads/ubports-installer_0.10.0_linux_x86_64.AppImage

General Notes

  • There is controversy about flakes, rather use channels (e.g. with niv)
  • Prins, P., Suresh, J. and Dolstra, E., "Nix fixes dependency hell on all Linux distributions," Archived December 26, 2008, at the Wayback Machine linux.com, December 22, 2008

Nix Pills

It provides a tutorial introduction into the Nix package manager and Nixpkgs package collection, in the form of short chapters called 'pills'.

Papers

Papers about Nix:

System information

nix-info -m

 - system: `"x86_64-linux"`
 - host os: `Linux 6.1.51, NixOS, 23.05 (Stoat), 23.05.3242.da5adce0ffaf`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.13.5`
 - channels(root): `"nixos-23.05"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

Search for packages

Search for options

Search which package owns a file

# Note how your shell prefix changes.
nix-shell -p nix-index

# Either build the index manually (requires >12GB RAM):
nix-index
# Or download weekly build:
mkdir -p ~/.cache/nix-index/ && wget -q -N https://github.com/nix-community/nix-index-database/releases/latest/download/index-x86_64-linux -O ~/.cache/nix-index/files

# Then search for a file
nix-locate --whole-name '/bash'

List files of package

Example for nano:

find $(nix-build '<nixpkgs>' -A nano --no-link)

Excerpt of the result:

/nix/store/jqvxmx65mfinbsm6db9kmcqmphl44xhp-nano-7.2/share/nano
/nix/store/jqvxmx65mfinbsm6db9kmcqmphl44xhp-nano-7.2/share/nano/asm.nanorc
/nix/store/jqvxmx65mfinbsm6db9kmcqmphl44xhp-nano-7.2/share/nano/autoconf.nanorc

Compare two versions of NixOS system profile

Get latest system profile. This is the profile (usually) being active after booting the system:

ls -1 /nix/var/nix/profiles/ | sort -t'-' -n -k2 | tail -n 1
#=> 120

Compare current with previous profile:

# https://stackoverflow.com/a/36641298
prev="$(ls -1 /nix/var/nix/profiles/ | sort -t'-' -n -k2 | tail -n 2 | head -n 1)"
curr="$(ls -1 /nix/var/nix/profiles/ | sort -t'-' -n -k2 | tail -n 1)"
nix --extra-experimental-features nix-command store diff-closures /nix/var/nix/profiles/"${prev}" /nix/var/nix/profiles/"${curr}"

Compare two arbitrary system profiles:

nix --extra-experimental-features nix-command store diff-closures /nix/var/nix/profiles/system-110-link /nix/var/nix/profiles/system-116-link

cpupower: 6.1.47 → 6.1.51
element-desktop: 1.11.38 → 1.11.40, +2218.9 KiB
element-web: 1.11.38 → 1.11.40, -73.1 KiB
exempi: 2.6.3 → 2.6.4
firefox: 116.0.3 → 117.0
firefox-unwrapped: 116.0.3 → 117.0, -292.6 KiB
gnome-shell-extension-openweather: ∅ → 121, +590.5 KiB
hm_fontconfigconf.d10hmfonts.conf: ∅ → ε
initrd: ∅ → ε
initrd-linux: 6.1.47 → 6.1.51
libcap: 2.68 → 2.69
linux: 6.1.47, 6.1.47-modules → 6.1.51, 6.1.51-modules, -11.8 KiB
meld: ∅ → 3.22.0, +3858.5 KiB
net-snmp: 5.9.3 → 5.9.4
nixos-system-yodaTab: 23.05.3085.2ab91c8d65c0 → 23.05.3242.da5adce0ffaf
openjdk: +19.5 KiB
python3.10-pygobject: +27.0 KiB
stage: ∅ → 1-init.sh, +29.5 KiB
tor-browser-bundle-bin: 12.5.2 → 12.5.3, +18.1 KiB
user: +2885.0 KiB

NixOS configuration debugging

Evaluating parts of the configuration.

First, start nix repl:

nix repl --file '<nixpkgs/nixos>' -I nixos-config=hosts/$(hostname)/configuration.nix

Example: config.home-manager

config.home-manager.
# Press `TAB`
#=> config.home-manager.backupFileExtension  config.home-manager.useUserPackages
#=> config.home-manager.extraSpecialArgs     config.home-manager.users
#=> config.home-manager.sharedModules        config.home-manager.verbose
#=> config.home-manager.useGlobalPkgs

Example: The home variable:

config.home-manager.users.yoda.home

Example: The value of one config option

# The following option is set to `"${config.xdg.dataHome}/.histfile";`
# where `config` is the Home Manager configuration.

config.home-manager.users.yoda.programs.zsh.history.path
#=> "/home/yoda/.local/share/.histfile"

Show Nix configuration

nix --extra-experimental-features nix-command show-config

Evaluate NixOS configuration to JSON

See also section "NixOS Configuration Debugging"!

This evaluates configuration.nix (single module):

NIXPKGS_ALLOW_UNFREE=1 nix-instantiate --strict --json --eval -E '
import ./hosts/yodaTab/configuration.nix  {
  config = {};
  pkgs = import <nixpkgs> {};
  lib = import <nixpkgs/lib>;
}
' > evaluated-config.json

Then open evaluated-config.json.

References

Some references to websites that helped me create this repository:

TODOs