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@0atman
Last active November 15, 2024 13:06
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A rebuild script that commits on a successful build
{
config,
pkgs,
options,
...
}: let
hostname = "oatman-pc"; # to alllow per-machine config
in {
networking.hostName = hostname;
imports = [
/etc/nixos/hardware-configuration.nix
(/home/oatman/dotfiles/nixos + "/${hostname}.nix")
];
}
#!/usr/bin/env bash
#
# I believe there are a few ways to do this:
#
# 1. My current way, using a minimal /etc/nixos/configuration.nix that just imports my config from my home directory (see it in the gist)
# 2. Symlinking to your own configuration.nix in your home directory (I think I tried and abandoned this and links made relative paths weird)
# 3. My new favourite way: as @clot27 says, you can provide nixos-rebuild with a path to the config, allowing it to be entirely inside your dotfies, with zero bootstrapping of files required.
# `nixos-rebuild switch -I nixos-config=path/to/configuration.nix`
# 4. If you uses a flake as your primary config, you can specify a path to `configuration.nix` in it and then `nixos-rebuild switch —flake` path/to/directory
# As I hope was clear from the video, I am new to nixos, and there may be other, better, options, in which case I'd love to know them! (I'll update the gist if so)
# A rebuild script that commits on a successful build
set -e
# Edit your config
$EDITOR configuration.nix
# cd to your config dir
pushd ~/dotfiles/nixos/
# Early return if no changes were detected (thanks @singiamtel!)
if git diff --quiet '*.nix'; then
echo "No changes detected, exiting."
popd
exit 0
fi
# Autoformat your nix files
alejandra . &>/dev/null \
|| ( alejandra . ; echo "formatting failed!" && exit 1)
# Shows your changes
git diff -U0 '*.nix'
echo "NixOS Rebuilding..."
# Rebuild, output simplified errors, log trackebacks
sudo nixos-rebuild switch &>nixos-switch.log || (cat nixos-switch.log | grep --color error && exit 1)
# Get current generation metadata
current=$(nixos-rebuild list-generations | grep current)
# Commit all changes witih the generation metadata
git commit -am "$current"
# Back to where you were
popd
# Notify all OK!
notify-send -e "NixOS Rebuilt OK!" --icon=software-update-available
@taiwithers
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Here's a version that's I edited to work with Home Manager and custom *.nix file locations, I've also added a segment to check for untracked *.nix files since these don't get picked up by git diff
Not sure if ether of those things are useful to anyone else but shrug

@Mjb141
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Mjb141 commented May 25, 2024

Thanks for sharing this script. Now, I won't ruin my system because I messed up my configuration.nix. One improvement that I made when I started using it was to handle the script itself the nix way by storing is a nixos-rebuild.nix file:

{
  config,
  pkgs,
  ...
}: {
  environment.systemPackages = with pkgs; [
    (writeShellScriptBin "nixos-rebuild.sh" ''
    // Script without shebang
        '')
  ];
}

And just importing it in my managed version of configuration.nix. This way, I don't need to think about shebang and my script is also versioned via NixOS using generations too.

Can you link how you've done this? I've imported such a file into my configuration.nix but it's not making the script findable on PATH.

@Lemm1
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Lemm1 commented May 26, 2024

Can you link how you've done this? I've imported such a file into my configuration.nix but it's not making the script findable on PATH.

You need to rebuild the system first use simple nixos-rebuild switch once so script is generated by nix and added to PATH

@Mjb141
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Mjb141 commented May 26, 2024

Yeah all good, got it working shortly afterwards. Added to it with a Home-Manager step as well, very useful script!

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ghost commented Jul 15, 2024

Hi Tris, thanks to you I benefit from NixOS and I recently stumbled to a tool called nh that can be integrated to your workflow, you might want to check it out.

@0atman
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0atman commented Jul 15, 2024

@ArgumentumAdUlgenum yeah! I also recently discovered nh (thanks to the #nix channel on my discord) - and really like it.

HOWEVER, I recently switched my whole setup away from flakes to get back unattended upgrade (and some other reasons) , which means I can't use nh (it requires flakes). However, as there are only 3 main features, according to the readme:

  • Tree of builds with nix-output-monitor
  • Visualization of the upgrade diff with nvd
  • Asking for confirmation before performing activation

... The only one of those features I didn't really have (due to my git diff printing) was the build tree visualising using nom, which is easy enough to add on to this existing script! 😁

For those who want it, the line is

sudo nixos-rebuild --upgrade switch --log-format internal-json |& nom --json

which outputs the log in json, that nom consumes.

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ghost commented Jul 25, 2024

So, I tried to make a flake free configuration and arrived at conclusion flakes makes it far easier to deal with dependencies to other nix projects like home-manager or nixvim.

As far as I know you use Nix to just configure your computer, your dotfiles are managed outside of Nix. If you ever decide to change from this paradigm, you might want to give flakes another chance.

See you later Tris.

@0atman
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0atman commented Jul 25, 2024

Yeah, I actually abandoned not having flakes enabled after a day - so many tools assume you've got a flakes system. The rust flake works very well, for instance. I'm down to use it for links to these other projects - but not core system stuff.

I'm sad though: My dream of unattended upgrades seems dead. By design, flakes don't update their lockfile without user input, right?
The difference between me and many nix folks is that I don't care about reproducibility. I care about stability and bleeding-edge features. Lucky for me, Nixos gives me that!

I did indeed trynixvim for a while, but lazynvim is turnkey, so I'm simply using that. Home Assistant is fine, but I don't think it makes sense for my low-stress life. I want my config to instantly change when I change a config file, not requiring a hm switch - an symlinks work great for that!
Using GNU Stow I run stow . on my dotfiles directory, and with no config, everything's symlinked into my home directory. I get config rollback with git, and given that neither HM or Stow is linked to my nixos system generations... feels like I'm not missing anything?

@taiwithers
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I'm sad though: My dream of unattended upgrades seems dead. By design, flakes don't update their lockfile without user input, right? The difference between me and many nix folks is that I don't care about reproducibility. I care about stability and bleeding-edge features. Lucky for me, Nixos gives me that!

Ditto on the reproducability (I want reproducability in my package set and configs but versions are unimportant to me). It's not quite "unattended", but you could add a nix flake update line into your rebuild script and update lock files that way

@0atman
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0atman commented Jul 25, 2024

Very good point. I could perhaps run that on a cron?

@ryuji-terix
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ryuji-terix commented Jul 26, 2024

@0atman You can create a systemd service with nixos that does it automagically

systemd.services.bleeding_edger = {
  enable = true;
  path = [ pkgs.nix ];
  serviceConfig = {
     ExecStart = "nix flake update";
   }
}

Extra help: https://discourse.nixos.org/t/creating-a-systemd-service-that-runs-a-nix-command/38437

@Lemm1
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Lemm1 commented Jul 26, 2024

I always thought that --update-input flag in system.autoUpgrade basically does nix flake update before schedules update. At least wiki says that it's enough for flake system to get autoupdates: https://nixos.wiki/wiki/Automatic_system_upgrades

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ghost commented Jul 26, 2024

Very good point. I could perhaps run that on a cron?

In my system nix flake update command requires sudo, I'm pretty sure this wasn't always the case though.

I did indeed trynixvim for a while, but lazynvim is turnkey, so I'm simply using that. Home Assistant is fine, but I don't think it makes sense for my low-stress life.

I also experienced the issue of not being able to set things too easily when using home-manager. So I use home-manager to set things like setting universal colorscheme with stylix, and configurations that I don't always mess with, I'm confident I want them in a certain way.

I used to configure my browser with Nix too but I stopped doing that since it was a pain Nix overwriting some of the things I changed between rebuilds every time. Stow is an amazing tool for your use-case though. I feel bad I didn't knew it i before i spent many months running mostly Arch.

so many tools assume you've got a flakes system

A wise man once told "Popularity Matters" in his "The Unreasonable Effectiveness Of Plain Text" video . Flakes, let alone still being labeled as a experimental feature, as far as i know 40% of Nix users use it. Probably has a higher margin on desktop usage.

@JustCoderdev
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New functionality implemented: instead of hiding the output of the rebuild script (creating anti-climatic moments) what about using the alternative screen buffer? So when the program is done all the logs go away and you're left with a pleasant 'Rebuild Completed' or not so pleasant 'Rebuild failed'

Final output

 /.dotfiles/nixos $ rebuild-system
Hostname not passed, defaulting to #acer
Analysing changes... Not found
Rebuilding NixOS... Done

[sudo] password for justcode:
NixOS Rebuild Completed!

 /.dotfiles/nixos $

Here the escape codes to enter alt screen buffer

# Enter alt-buff and clear screen
echo -ne "\033[?1049h\033[H"

# Exit alt-buff
echo -ne "\033[?1049l"

And here's the snippet that I use

# Rebuild system
echo -n "Rebuilding NixOS... "
echo -ne "\033[?1049h\033[H" # enter alt-buff and clear
echo "Rebuilding NixOS..."

set +o pipefail # Disable pipafail since we check ourselves
# shellcheck disable=SC2024 #ah the irony
sudo nixos-rebuild switch --show-trace --flake ".#${HOST_SHELL}" 2>&1 | tee .nixos-switch.log
exit_code="${PIPESTATUS[0]}"
set -o pipefail # Re-enable pipefail

# Wait a bit before exiting buffer
echo  -e "\n\033[34mNixOS rebuild completed\033[0m (code: $exit_code)"
echo -ne "\rExit in 3" && sleep 1
echo -ne "\rExit in 2" && sleep 1
echo -ne "\rExit in 1" && sleep 1
echo -ne "\033[?1049l" # exit alt-buff

# Check exit code of nixos-rebuild and act accordingly
if [[ "${exit_code}" == 0 ]]; then
	echo -e "Done\n"
...

@0atman
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0atman commented Aug 13, 2024

Holy carp, that's some deep magic there, thank you! Will experiment

@JustCoderdev
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JustCoderdev commented Aug 14, 2024

@0atman You can test the full version of the script by taking it from my dotfiles. This way you can get a feel if you like it or not [link]

let me know ;)

edit: You might want to disable certain stuff like the automatic host recognition, the flake auto-update (based on the current host), the auto-restore (so that it can properly detect if it's rebuilding with changes after a failed attempt) and the auto-commit (for obvious reasons)

@0atman
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0atman commented Aug 14, 2024

Thank you! Hopefully useful for others too!

@JustCoderdev
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I found out something very useful

You can unlink nixos files without extra permissions and on the next rebuild they will get recreated

This means that when you want to quickly iterate over a configuration (waybar for example) you can remove the nixos link, point it to your configuration folder, modify it and test things out without having to rebuild

When you're done just rebuild and nixos will bake the new config into the next generation

@S1rDev10us
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Isn't the current autoformatting command forgetting to popd on formatting failure?

@0atman
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0atman commented Aug 27, 2024

@S1rDev10us huh, I don't think pushd/popd work in the way I (or maybe you!) think. Perhaps someone smarter than I can explain what happens to the directory stack on an early exit?

A script I just tried that surprised me:

#!/usr/bin/env bash
set -e
pushd ~/Music
pwd
exit 1
# after exit, cwd is back where we started, despite not popd-ing

@JustCoderdev
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@0atman As far I know pushd and popd act only inside of the shell that get's created when you execute the script, like if you had two terminals and you changed directory in one of them. Once the script has terminated it exits to the "outer shell" (bash or zsh) and resume the previous environment

@0atman
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0atman commented Aug 28, 2024

oh of course! it's running in the shebang's process, not hijacking the outer shell 😅

@JustCoderdev
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I have a laptop with only two cores and - since everytime I started a rebuild it would freeze my desktop - I implemented the simplest throttling mechanism to tell nixos-rebuild to use only half of the available cores (snippet below)

# Detect processors
procs="$(nproc)"
if [ -z "${procs:-}" ]; then
	echo "No processors detected! Assuming 2..."
	procs="2"
fi

hprocs="$(( procs / 2 ))"
echo "Detected ${procs} processors, using ${hprocs} of them"

nixos-rebuild switch --max-jobs "${hprocs}" #...

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