Nix vanity store paths

Published 2025-03-27 on Farid Zakaria's Blog

Nix is great, but it can be a bit dreary continuously looking at the endless /nix/store paths with their varied letters.

Wouldn’t it be great if we can inject a little vanity into our /nix/store paths?

Vanity Addresses

A vanity address is one where we put a desired string (farid) in our /nix/store path like /nix/store/farid8x0yrdpavxxki9vg9spx2xbjb1d-nix-vanity-d915ed2

Why would we want to do this? Because we can! 😏

Let’s start off with a little demo.

Pick any derivation from your /nix/store. In my example, I’m picking a derivation I made /nix/store/cdqs8ir4pzwpl512dp86nk9xhq9bfmcv-vanity-path.drv

Simply run the tool nix-vanity. Let it crunch through a bunch of possible derivations until it emits:

# n.b. write out the discovered derivation to a file with
# the same name.
> nix-vanity -prefix /nix/store/farid \
  /nix/store/cdqs8ir4pzwpl512dp86nk9xhq9bfmcv-vanity-path.drv \
  > vanity-path.drv
time=2025-03-27T20:40:40.941-07:00 level=INFO msg="Loading base derivation" path=/nix/store/cdqs8ir4pzwpl512dp86nk9xhq9bfmcv-vanity-path.drv
time=2025-03-27T20:40:40.941-07:00 level=INFO msg="Calculating input derivation replacements..."
time=2025-03-27T20:40:40.952-07:00 level=INFO msg="Finished calculating input derivation replacements."
time=2025-03-27T20:40:40.952-07:00 level=INFO msg="Starting workers" count=16
⠙ Searching for prefix... (18104594, 292130 drv/s) [1m0s] time=2025-03-27T20:41:41.189-07:00 level=INFO msg="Prefix found!" seed=18131442 output_name=out path=/nix/store/faridj55f0h38jcnsh89sgp2fsbhv3ws-vanity-path
⠹ Searching for prefix... (18131450, 301001 drv/s) [1m0s] time=2025-03-27T20:41:41.189-07:00 level=INFO msg="Successfully found seed" seed=18131442
time=2025-03-27T20:41:41.189-07:00 level=INFO msg="Writing successful derivation to stdout..."
time=2025-03-27T20:41:41.189-07:00 level=INFO msg="All workers finished."

We can now add our modified derivation back to the /nix/store

> nix-store --add vanity-path.drv
/nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv

Finally, let’s realize our modified derivation and validate we have our vanity store path:

> nix-store --realize /nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv
this derivation will be built:
  /nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv
building '/nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv'...
warning: you did not specify '--add-root'; the result might be removed by the garbage collector
/nix/store/faridj55f0h38jcnsh89sgp2fsbhv3ws-vanity-path

Huzzah! /nix/store/faridj55f0h38jcnsh89sgp2fsbhv3ws-vanity-path 💥

Very cool! How does this all work? 🤓

The concept is rather simple. The /nix/store path is calculated from the hash of the derivation.

By injecting a new environment variable VANITY_SEED we can attempt different possible store paths.

> nix derivation show /nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv 
{
  "/nix/store/mw0ay18bx93r5syyscfmdy1s6jgjxk31-vanity-path.drv": {
    "args": [
      "-e",
      "/nix/store/v6x3cs394jgqfbi0a42pam708flxaphh-default-builder.sh"
    ],
    "builder": "/nix/store/8vpg72ik2kgxfj05lc56hkqrdrfl8xi9-bash-5.2p37/bin/bash",
    "env": {
      "VANITY_SEED": "18131442",

Although the idea 💡 was simple, the implementation in code was a bit more arduous.

Thankfully there was a decent starting point with go-nix which I augmented.

You can checkout the command at https://github.com/fzakaria/go-nix/tree/vanity

> go run ./cmd/nix-vanity ...

My next post might go into how exactly the store path is calculated from a derivation file. It was not as straightforward as I had imagined.

Be careful how long of a prefix you pick for your vanity. 🧐

Nix store paths can be any 32 letters from 0123456789abcdfghijklmnpqrsvwxyz (32 possibilities).

That means if I want a single letter for my prefix, it is a 1/32 probability ~ 3% chance.

For two consecutive letters, there are 32 * 32 total possibilities. If I wanted a single entry that would be 1/(32 * 32) ~ 0.098% chance.

This is exponential and can blow up pretty fast as the search space becomes 32^N.

Prefix Length (N)	Expected Attempts	Time @ 300,904 drv/s
1	32	< 1s
2	1,024	< 1s
3	32,768	< 1s
4	1,048,576	3.48 s
5	33,554,432	111.5 s (≈1.86 minutes)
6	1,073,741,824	3,567 s (≈59.45 minutes)
7	34,359,738,368	114,209 s (≈31.72 hours)

I wrote the code in golang with concurrency in mind but even on a machine with 128 cores (AMD Ryzen Threadripper 3990X 64-Core Processor ) it tops out at trying 300904 drv/s.

Either way, for something small like farid (5 letters), it’s kind of nice to jazz up ✨ the store paths.

You could even build a complete /nix/store where every entry is prefixed with a desired vanity string 😈.

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