2020-07-23 00:17:48 +03:00
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# Garbage Collection
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`nix-env` operations such as upgrades (`-u`) and uninstall (`-e`) never
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actually delete packages from the system. All they do (as shown above)
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is to create a new user environment that no longer contains symlinks to
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the “deleted” packages.
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Of course, since disk space is not infinite, unused packages should be
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removed at some point. You can do this by running the Nix garbage
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collector. It will remove from the Nix store any package not used
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(directly or indirectly) by any generation of any profile.
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Note however that as long as old generations reference a package, it
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will not be deleted. After all, we wouldn’t be able to do a rollback
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otherwise. So in order for garbage collection to be effective, you
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should also delete (some) old generations. Of course, this should only
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be done if you are certain that you will not need to roll back.
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To delete all old (non-current) generations of your current profile:
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-env --delete-generations old
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```
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2020-07-23 00:17:48 +03:00
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Instead of `old` you can also specify a list of generations, e.g.,
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-env --delete-generations 10 11 14
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```
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2020-07-23 00:17:48 +03:00
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To delete all generations older than a specified number of days (except
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the current generation), use the `d` suffix. For example,
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-env --delete-generations 14d
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```
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2020-07-23 00:17:48 +03:00
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deletes all generations older than two weeks.
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After removing appropriate old generations you can run the garbage
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collector as follows:
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-store --gc
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```
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2020-07-23 00:17:48 +03:00
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The behaviour of the gargage collector is affected by the
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`keep-derivations` (default: true) and `keep-outputs` (default: false)
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options in the Nix configuration file. The defaults will ensure that all
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derivations that are build-time dependencies of garbage collector roots
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will be kept and that all output paths that are runtime dependencies
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will be kept as well. All other derivations or paths will be collected.
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(This is usually what you want, but while you are developing it may make
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sense to keep outputs to ensure that rebuild times are quick.) If you
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are feeling uncertain, you can also first view what files would be
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deleted:
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-store --gc --print-dead
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```
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2020-07-23 00:17:48 +03:00
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Likewise, the option `--print-live` will show the paths that *won’t* be
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deleted.
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There is also a convenient little utility `nix-collect-garbage`, which
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when invoked with the `-d` (`--delete-old`) switch deletes all old
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generations of all profiles in `/nix/var/nix/profiles`. So
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2020-07-31 16:43:25 +03:00
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```console
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$ nix-collect-garbage -d
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```
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2020-07-23 00:17:48 +03:00
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is a quick and easy way to clean up your system.
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