From e19db18b71adcdf4aad9e28c4ed322f98704064f Mon Sep 17 00:00:00 2001 From: Daniel Langbein Date: Mon, 11 Nov 2024 11:48:49 +0100 Subject: [PATCH] fix: nix garbage collection --- NixOS.md | 59 ++++++++++++++++++++++++---------------------- modules/nix-gc.nix | 12 ++++++---- 2 files changed, 39 insertions(+), 32 deletions(-) diff --git a/NixOS.md b/NixOS.md index 636b3e6..560678c 100644 --- a/NixOS.md +++ b/NixOS.md @@ -21,8 +21,8 @@ This document contains general notes about NixOS that are independent of my NixO * [Nix profiles](#nix-profiles) * [Switch to previous system profile](#switch-to-previous-system-profile) * [List system profiles](#list-system-profiles) - * [Garbage collection - Keep most recent X system profiles](#garbage-collection---keep-most-recent-x-system-profiles) - * [Garbage collection - Delete system profiles older than X days](#garbage-collection---delete-system-profiles-older-than-x-days) + * [Deleting generations - Keep most recent X system profiles](#deleting-generations---keep-most-recent-x-system-profiles) + * [Garbage collection - Delete unreachable store objects](#garbage-collection---delete-unreachable-store-objects) * [why-depends: Why is a package/dependency installed](#why-depends-why-is-a-packagedependency-installed) * [Compare two system profiles](#compare-two-system-profiles) * [NixOS configuration debugging](#nixos-configuration-debugging) @@ -448,33 +448,24 @@ sudo reboot ### List system profiles -Not sure why 432 is marked as current. It is the default generation that gets activated on next boot. The currently active generation is, however, 429. - ```shell sudo nix-env --list-generations --profile /nix/var/nix/profiles/system ``` ```console ... - 428 2024-03-06 12:37:56 - 429 2024-03-07 11:27:20 - 430 2024-03-10 12:48:34 - 431 2024-03-11 11:18:57 - 432 2024-03-12 22:19:53 (current) + 282 2024-11-10 12:53:25 + 283 2024-11-11 10:45:46 (current) ``` ```shell ls -l /nix/var/nix/profiles/ ``` ```console -lrwxrwxrwx 1 root root 43 Dez 14 12:21 default -> /nix/var/nix/profiles/per-user/root/profile -drwxr-xr-x 1 root root 16 Sep 1 2023 per-user -lrwxrwxrwx 1 root root 15 Mär 12 22:19 system -> system-432-link -... -lrwxrwxrwx 1 root root 77 Mär 6 12:37 system-428-link -> /nix/store/damngdyial0i96xa46csdqk36j2njavi-nixos-system-yodaTux-23.11pre-git -lrwxrwxrwx 1 root root 77 Mär 7 11:27 system-429-link -> /nix/store/k7c7576sz868gzjci1z6l6nzmdnpd6xr-nixos-system-yodaTux-23.11pre-git -lrwxrwxrwx 1 root root 77 Mär 10 12:48 system-430-link -> /nix/store/7468m7rgk425kb23aq222a498ynfqdkc-nixos-system-yodaTux-23.11pre-git -lrwxrwxrwx 1 root root 77 Mär 11 11:18 system-431-link -> /nix/store/r51yw36ddfxq8hdsz2mm6axpbqvjaigy-nixos-system-yodaTux-23.11pre-git -lrwxrwxrwx 1 root root 77 Mär 12 22:19 system-432-link -> /nix/store/i9pxh3ax6m0yr7xlk7y7c5xdzp74xqi4-nixos-system-yodaTux-23.11pre-git +lrwxrwxrwx 1 root root 43 Dez 26 2023 default -> /nix/var/nix/profiles/per-user/root/profile +drwxr-xr-x 1 root root 16 Aug 15 2023 per-user +lrwxrwxrwx 1 root root 15 Nov 11 10:45 system -> system-283-link +lrwxrwxrwx 1 root root 77 Nov 10 12:53 system-282-link -> /nix/store/jb5krdbbylwwgvxiadiv6fxja2zgc4h3-nixos-system-yodaTab-24.05pre-git +lrwxrwxrwx 1 root root 77 Nov 11 10:45 system-283-link -> /nix/store/jf7ml8jzxrmg9djhfr8szq2f19hxysn5-nixos-system-yodaTab-24.05pre-git ``` The currently running system. This is the currently active generation. By comparing the store path with the above output, we see that it matches generation 429. @@ -483,33 +474,45 @@ The currently running system. This is the currently active generation. By compar ls -l /run/current-system ``` ```console -lrwxrwxrwx 1 root root 77 Mär 9 12:44 /run/current-system -> /nix/store/k7c7576sz868gzjci1z6l6nzmdnpd6xr-nixos-system-yodaTux-23.11pre-git +lrwxrwxrwx 1 root root 77 Nov 11 10:46 /run/current-system -> /nix/store/jf7ml8jzxrmg9djhfr8szq2f19hxysn5-nixos-system-yodaTab-24.05pre-git ``` -### Garbage collection - Keep most recent X system profiles +### Deleting generations - Keep most recent X system profiles -A NixOS config example is given in [base.nix](modules/base.nix). +https://nix.dev/manual/nix/2.18/command-ref/nix-env/delete-generations + +> Periodically deleting old generations is important to make garbage collection effective. The is because profiles are also garbage collection roots. + +A NixOS config example is given in [nix-gc.nix](modules/nix-gc.nix). ```shell sudo nix-env --delete-generations +7 --profile /nix/var/nix/profiles/system ``` -TODO: Should we run `sudo nix-collect-garbage --delete-old` after the above? +After deleting some generations, it is still necessary to collect garbage in order to free up your system. See below. -### Garbage collection - Delete system profiles older than X days +### Garbage collection - Delete unreachable store objects + +https://nix.dev/manual/nix/2.18/command-ref/nix-collect-garbage + +> `nix-collect-garbage` deletes all unreachable store objects in the Nix store to clean up your system. * https://nixos.org/manual/nix/stable/package-management/garbage-collection.html * https://discourse.nixos.org/t/why-doesnt-nix-collect-garbage-remove-old-generations-from-efi-menu/17592/4 -A NixOS config example is given in [base.nix](modules/base.nix). - -Run manually for all profiles: +First delete unreachable store objects: ```shell -sudo nix-collect-garbage --delete-older-than 14d +# Delete unreachable store objects +sudo nix-collect-garbage + +# Deletes all except the currently active generation prior to deleting unreachable store objects +#sudo nix-collect-garbage --delete-old +# Deletes all generations older than 14d prior to deleting unreachable store objects +#sudo nix-collect-garbage --delete-older-than 14d ``` -Remove leftover EFI entries of removed generations: +Then remove leftover EFI entries of deleted generations: ```shell sudo /run/current-system/bin/switch-to-configuration boot diff --git a/modules/nix-gc.nix b/modules/nix-gc.nix index a9c8e7b..93c3454 100644 --- a/modules/nix-gc.nix +++ b/modules/nix-gc.nix @@ -1,10 +1,11 @@ { config, pkgs, ... }: { - # Keep only the 7 most recent system generations. + # Delete all system generations except the 7 most recent ones. + # Then delete all unreachable store objects. # # Based on https://github.com/NixOS/nixpkgs/blob/nixos-23.11/nixos/modules/services/misc/nix-gc.nix - # - # Alternatively: Delete generations older than 7 days + + # Alternative: Delete generations older than 7 days and then delete unreachable store objects # https://nixos.wiki/wiki/Storage_optimization#Automation #nix.gc = { # automatic = true; @@ -29,8 +30,10 @@ }; }; + # View generated systemd service config with: + # cat "$(systemctl show -P FragmentPath nix-gc-7.service)" | grep ExecStart systemd.services."nix-gc-7" = { - description = "Keep only the most recent 7 system generations"; + description = "rm old system generations and unreachable store objects"; conflicts = [ "shutdown.target" "sleep.target" ]; before = [ "shutdown.target" "sleep.target" ]; @@ -45,6 +48,7 @@ script = '' ${config.nix.package.out}/bin/nix-env --delete-generations +7 --profile /nix/var/nix/profiles/system + ${config.nix.package.out}/bin/nix-collect-garbage ''; }; }