NixOS / NixOS/nix

Nix >= 2.30 multiuser fails to install on Ubuntu 25.10 (questing) beta/daily

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Description

Platform

  • Linux: Ubuntu 25.10. Tried both with beta1 as well as a daily version as of September 28th, 2025
  • macOS
  • WSL

Additional information

System installed from scratch

Output

Output
./install --daemon < /dev/null
...
[output suppressed, all works so far]
...

~~> Setting up the default profile
installing 'nix-2.31.2'
building '/nix/store/g30g3gcmq5fly1p3qga608wisvhkczjs-user-environment.drv'...
error: cannot read directory "/nix/store/i91hkfq9raq9qznwjrd59mlf1zb7nlpq-nix-2.31.2": Permission denied
error: Cannot build '/nix/store/g30g3gcmq5fly1p3qga608wisvhkczjs-user-environment.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/yrslk7w7pgnrfcdflb3ybmlzf0zf0njy-user-environment

---- oh no! --------------------------------------------------------------------
Oh no, something went wrong. If you can take all the output and open
an issue, we'd love to fix the problem so nobody else has this issue.

:(

We'd love to help if you need it.

You can open an issue at
https://github.com/NixOS/nix/issues/new?labels=installer&template=installer.md

Or get in touch with the community: https://nixos.org/community

Fails with:

  • nix-2.31.2
  • nix-2.30.3

However works without problems with nix-2.29.2.

This issue is similar to https://github.com/NixOS/nix/issues/13252, also a permission error but of different kind. Note that I also tested on 24.04 and didn't have a problem installing 2.31.2.

Checklist


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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the multiuser installer on a fresh Ubuntu 25.10 beta or daily system with Nix 2.30.3 or 2.31.2, and compare it with Nix 2.29.2 and Ubuntu 24.04. Done means the installation completes, including default profile setup, without the permission-denied error reading the Nix store.

Written by the indexing model from the issue text.

Assessment

Tech stack
ubuntu
Domain
operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
35/100

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