Nix Meddle - bind-mount + unshare = safe hacking in your nix-path

The idea

you have that one configfile which is just a link to your nix store (e.g. vim config, etc.). Now for some reason after thw latest rebuild there is a small mistake in that configfile and you wanna change it quickly to see if you can fix it.

Usually you would change the Nix configfile, nixos/homemanager/... rebuild, test, realise it’s still wrong, repeat until fixed. This is especially annoying if the only “quick” solution is to rebuild your whole config - which can take ages.

With nix-meddle you can make a nix path “writable”. run the program and select a path from the nix store.
The nix path will be copied to ~/.local/share/meddle/${DATE}_${derivation_name} and it shows the 2 commands used to first unshare (a.k.a. make it possible to bind-mount without root) and then mount the directory into the nix store.
Meddle and test around as you wish, and after ctrl-c (exiting the unshare), the bind mount will be gone.

State of the project

I’ve hacked together a more or less working version of nix meddle after having thought about it for over a year.

It’s not pretty at all and you’ll even have to manually copy paste 2 commands it shows you. But I thought maybe that’s already enough for someone else, too :slight_smile:


Given it’s very prototypical state it only works with flakes :frowning:
But with flakes it’s really easy to use :slight_smile:

nix run github:Melkor333/nix-meddle

Follow the questions and if everything goes well, copy & paste the 2 commands. Be aware: the commands must be pasted separately, because otherwise the second command is ignored (the first command starts a subshell)
[Not requiring to paste these commands is an open TODO]

Edit: I never again write an article on my phone. My phone keyboard is so broken!