Dennis HilkLinux Fix LabDE

NixOS & Configuration

The Nix command requires a disabled experimental feature

Nix rejects flakes or the modern CLI before evaluation. Check the active binary and settings scope, then enable only the features the workflow needs.

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On this page
  1. Symptoms & scope
  2. Possible causes
  3. Diagnose safely
  4. Evidence-guided next steps
  5. References & review
  6. Related problems

Symptoms & scope

  • The command says experimental Nix feature flakes or nix-command is disabled.
  • A privileged invocation behaves differently from the user's shell.

Relevant environment

Nix installations using feature-gated nix-command and flakes; defaults vary by installation.

Recognizable messages (synthetic examples)
error: experimental Nix feature 'flakes' is disabled; add '--extra-experimental-features flakes' to enable it

The failure precedes evaluation of the flake's outputs.

error: experimental Nix feature 'nix-command' is disabled; add '--extra-experimental-features nix-command' to enable it

This can fail even before flakes are involved.

Possible causes

These are possible explanations, not a confirmed diagnosis. Several independent faults can coexist.

  • The required feature may not be enabled in the configuration read by that command.
  • Another Nix executable or a different user configuration can produce different effective settings.

Diagnose safely

Run one command at a time in the relevant session. Read the explanation first. Uppercase placeholders need your own values; tools and privileges vary by distribution. These commands are displayed here and never executed by the website.

Check 1

Reads the Nix version without building or evaluating a flake; run in the failing shell.

nix --version

Interpret the result: Compare the actual executable version with the installed manual. A tutorial's feature assumptions may not match this installation.

Check 2

Reads usual global and user settings; a missing user file is normal, and included files may require separate inspection.

rg -n 'experimental-features|include' /etc/nix/nix.conf ~/.config/nix/nix.conf

Interpret the result: Check whether nix-command and flakes are present in the relevant scope. Root commands do not necessarily read the user's file.

Evidence-guided next steps

Enable the required feature for one command

If this is an occasional flake workflow, add --extra-experimental-features 'nix-command flakes' to that Nix command where supported. This makes the requirement explicit without a permanent settings edit.

Precautions: Experimental interfaces can change. A feature flag does not make an arbitrary flake trusted; inspect its source before building.

Recovery / rollback: Remove the per-command flag to restore the original invocation; no persistent feature state was changed.

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Declare the needed features persistently

If flakes are an intended part of the NixOS configuration, declare nix.settings.experimental-features with the needed nix-command and flakes values, preserving other intentionally enabled features. Build and activate through the existing working workflow.

Precautions: Do not edit generated /etc/nix/nix.conf as the long-term NixOS source. Keep a route that can rebuild the configuration after reverting.

Recovery / rollback: Restore the prior declarative feature list and generation or remove the user-level setting you added.

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References & review

This guide was prepared from primary project or distribution sources and reviewed on the date shown. This is an editorial source check, not evidence that a fix was reproduced on your hardware. Diagnostic log examples are synthetic fixtures. Version-dependent details must be checked against your installed release.