65 lines
1.8 KiB
Markdown
65 lines
1.8 KiB
Markdown
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# Cleaning the Nix Store {#sec-nix-gc}
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Nix has a purely functional model, meaning that packages are never
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upgraded in place. Instead new versions of packages end up in a
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different location in the Nix store (`/nix/store`). You should
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periodically run Nix's *garbage collector* to remove old, unreferenced
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packages. This is easy:
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```ShellSession
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$ nix-collect-garbage
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```
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Alternatively, you can use a systemd unit that does the same in the
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background:
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```ShellSession
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# systemctl start nix-gc.service
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```
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You can tell NixOS in `configuration.nix` to run this unit automatically
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at certain points in time, for instance, every night at 03:15:
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```nix
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{
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nix.gc.automatic = true;
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nix.gc.dates = "03:15";
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}
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```
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The commands above do not remove garbage collector roots, such as old
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system configurations. Thus they do not remove the ability to roll back
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to previous configurations. The following command deletes old roots,
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removing the ability to roll back to them:
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```ShellSession
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$ nix-collect-garbage -d
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```
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You can also do this for specific profiles, e.g.
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```ShellSession
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$ nix-env -p /nix/var/nix/profiles/per-user/eelco/profile --delete-generations old
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```
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Note that NixOS system configurations are stored in the profile
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`/nix/var/nix/profiles/system`.
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Another way to reclaim disk space (often as much as 40% of the size of
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the Nix store) is to run Nix's store optimiser, which seeks out
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identical files in the store and replaces them with hard links to a
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single copy.
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```ShellSession
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$ nix-store --optimise
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```
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Since this command needs to read the entire Nix store, it can take quite
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a while to finish.
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## NixOS Boot Entries {#sect-nixos-gc-boot-entries}
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If your `/boot` partition runs out of space, after clearing old profiles
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you must rebuild your system with `nixos-rebuild boot` or `nixos-rebuild
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switch` to update the `/boot` partition and clear space.
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