# Name

`nix-collect-garbage` - delete unreachable [store objects]

# Synopsis

`nix-collect-garbage` [`--delete-old`] [`-d`] [`--delete-older-than` *period*] [`--max-freed` *bytes*] [`--dry-run`]

# Description

The command `nix-collect-garbage` is mostly an alias of [`nix-store --gc`](@docroot@/command-ref/nix-store/gc.md).
That is, it deletes all unreachable [store objects] in the Nix store to clean up your system.

However, it provides two additional options,
[`--delete-old`](#opt-delete-old) and [`--delete-older-than`](#opt-delete-older-than),
which also delete old [profiles], allowing potentially more [store objects] to be deleted because profiles are also garbage collection roots.
These options are the equivalent of running
[`nix-env --delete-generations`](@docroot@/command-ref/nix-env/delete-generations.md)
with various augments on multiple profiles,
prior to running `nix-collect-garbage` (or just `nix-store --gc`) without any flags.

> **Note**
>
> Deleting previous configurations makes rollbacks to them impossible.

These flags should be used with care, because they potentially delete generations of profiles used by other users on the system.

## Locations searched for profiles

`nix-collect-garbage` cannot know about all profiles; that information doesn't exist.
Instead, it looks in a few locations, and acts on all profiles it finds there:

1. The default profile locations as specified in the [profiles] section of the manual.

2. > **NOTE**
   >
   > Not stable; subject to change
   >
   > Do not rely on this functionality; it just exists for migration purposes and may change in the future.
   > These deprecated paths remain a private implementation detail of Nix.

   `$NIX_STATE_DIR/profiles` and `$NIX_STATE_DIR/profiles/per-user`.

   With the exception of `$NIX_STATE_DIR/profiles/per-user/root` and `$NIX_STATE_DIR/profiles/default`, these directories are no longer used by other commands.
   `nix-collect-garbage` looks there anyways in order to clean up profiles from older versions of Nix.

# Options

These options are for deleting old [profiles] prior to deleting unreachable [store objects].

- <span id="opt-delete-old">[`--delete-old`](#opt-delete-old)</span> / `-d`

  Delete all old generations of profiles.

  This is the equivalent of invoking [`nix-env --delete-generations old`](@docroot@/command-ref/nix-env/delete-generations.md#generations-old) on each found profile.

- <span id="opt-delete-older-than">[`--delete-older-than`](#opt-delete-older-than)</span> *period*

  Delete all generations of profiles older than the specified amount (except for the generations that were active at that point in time).
  *period* is a value such as `30d`, which would mean 30 days.

  This is the equivalent of invoking [`nix-env --delete-generations <period>`](@docroot@/command-ref/nix-env/delete-generations.md#generations-time) on each found profile.
  See the documentation of that command for additional information about the *period* argument.

  - <span id="opt-max-freed">[`--max-freed`](#opt-max-freed)</span> *bytes*

<!-- duplication from https://github.com/NixOS/nix/blob/442a2623e48357ff72c77bb11cf2cf06d94d2f90/doc/manual/source/command-ref/nix-store/gc.md?plain=1#L39-L44 -->

  Keep deleting paths until at least *bytes* bytes have been deleted,
  then stop. The argument *bytes* can be followed by the
  multiplicative suffix `K`, `M`, `G` or `T`, denoting KiB, MiB, GiB
  or TiB units.
  
{{#include ./opt-common.md}}

{{#include ./env-common.md}}

# Example

To delete from the Nix store everything that is not used by the current
generations of each profile, do

```console
$ nix-collect-garbage -d
```