DOKK / manpages / debian 13 / nix-bin / nix-collect-garbage.1.en
nix-collect-garbage(1) General Commands Manual nix-collect-garbage(1)

nix-collect-garbage - delete unreachable store objects

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

The command nix-collect-garbage is mostly an alias of nix-store --gc. 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 and --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 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.

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.

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

•
--delete-old / -d
Delete all old generations of profiles.
This is the equivalent of invoking nix-env --delete-generations old on each found profile.
•
--delete-older-than 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> on each found profile. See the documentation of that command for additional information about the period argument.
•
--max-freed bytes

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}}

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

$ nix-collect-garbage -d