Storage optimization - Revision history

Cartwatson: rm deprecated link to options: min-free, max-free. Replaced with link to `nix.extraOptions` with correct template

2026-01-23T21:53:48Z

rm deprecated link to options: min-free, max-free. Replaced with link to `nix.extraOptions` with correct template

← Older revision		Revision as of 21:53, 23 January 2026
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	This can result in redownloads (tarballs fetched with <code>import (builtins.fetchTarball ...)</code> for example are not referenced anywhere and removed on GC), but it frees you from runnning GC manually.		This can result in redownloads (tarballs fetched with <code>import (builtins.fetchTarball ...)</code> for example are not referenced anywhere and removed on GC), but it frees you from runnning GC manually.

	It is also possible to automatically run garbage collection whenever there is not enough space left.<ref group="cf.">{{~~nix~~:option\|min-free}} and ~~{{nix:option\|~~max-free}}</ref> For example, to free up to 1GiB whenever there is less than 100MiB left:		It is also possible to automatically run garbage collection whenever there is not enough space left.<ref group="cf.">{{Nixos:option\|nix.extraOptions}}: min-free and max-free</ref> For example, to free up to 1GiB whenever there is less than 100MiB left:

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">

DoggoBit: propose merge with Nix store

2025-06-14T21:34:36Z

propose merge with Nix store

← Older revision		Revision as of 21:34, 14 June 2025
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			{{Merge\|Nix store}}

	A recurring problem with NixOS is lack of space on <code>/</code>. Even if you only occasionally use Nix, it is easy for <code>/nix/store</code> to grow beyond reasonable sizes. What follows are generic notes on how to reduce the growth of the [[Nix store]].		A recurring problem with NixOS is lack of space on <code>/</code>. Even if you only occasionally use Nix, it is easy for <code>/nix/store</code> to grow beyond reasonable sizes. What follows are generic notes on how to reduce the growth of the [[Nix store]].

DoggoBit: /* Garbage collection */ In general a user reading this section will care about removing old NixOS generations first. Thus, I moved the section above the GC roots details

2025-06-06T15:28:48Z

Garbage collection: In general a user reading this section will care about removing old NixOS generations first. Thus, I moved the section above the GC roots details

@@ Line 26: / Line 26: @@
 By default, the Nix store will not remove any entries that are no longer used, thus it can accumulate derivations you might no longer need.<ref group="cf.">[https://nixos.org/nix/manual/#sec-garbage-collection Nix Manual, 11. Garbage Collection]</ref> They can be deleted with {{ic|nix-collect-garbage}} <ref group="cf.">{{man|nix-collect-garbage|sec=1}}</ref> or {{ic|nix-store --gc}}.<ref group="cf.">{{man|nix-store|sec=1}}, under {{ic|OPERATION --GC}}</ref>
 Note that if a result file still exists in the file system, and your Nix configuration has both <code>keep-outputs = true</code> and <code>keep-derivations = true</code>, all the dependencies used to build it will be kept. To see which result files prevent garbage collection, run:
@@ Line 31: / Line 52: @@
 <syntaxhighlight lang="console">
 $ nix-store --gc --print-roots
 ...
 /nix/var/nix/profiles/per-user/root/channels-4-link -> /nix/store/254b6pkhhnjywvj5c0lp2vdai8nz4p0g-user-environment
 /nix/var/nix/profiles/system-398-link -> /nix/store/wmndyzzrbc9fyjw844jmvzwgwgcinq7s-nixos-system-iron-16.0916.09pre.custom
@@ Line 97: / Line 100: @@
 Look for system derivations in particular. Those are created on many occasions, for example when running <code>nixos-rebuild  build-vm</code>
 === Reboot ===
 As you see, the reference in <code>/run/booted-system</code> is a GC root, so it won't be cleared until reboot. If you don't want to reboot, just <code>rm /run/booted-system</code> that link and rerun <code>sudo nix-collect-garbage</code>.

DoggoBit: /* Garbage collection */ Small improvement on phrasing

2025-06-06T15:22:16Z

Garbage collection: Small improvement on phrasing

← Older revision		Revision as of 15:22, 6 June 2025
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	== Garbage collection ==		== Garbage collection ==

	~~The~~ Nix store ~~accumulates~~ entries ~~which~~ are no longer ~~useful~~.<ref group="cf.">[https://nixos.org/nix/manual/#sec-garbage-collection Nix Manual, 11. Garbage Collection]</ref> They can be deleted with {{ic\|nix-collect-garbage}} <ref group="cf.">{{man\|nix-collect-garbage\|sec=1}}</ref> or {{ic\|nix-store --gc}}.<ref group="cf.">{{man\|nix-store\|sec=1}}, under {{ic\|OPERATION --GC}}</ref>		By default, the Nix store will not remove any entries that are no longer used, thus it can accumulate derivations you might no longer need.<ref group="cf.">[https://nixos.org/nix/manual/#sec-garbage-collection Nix Manual, 11. Garbage Collection]</ref> They can be deleted with {{ic\|nix-collect-garbage}} <ref group="cf.">{{man\|nix-collect-garbage\|sec=1}}</ref> or {{ic\|nix-store --gc}}.<ref group="cf.">{{man\|nix-store\|sec=1}}, under {{ic\|OPERATION --GC}}</ref>

	Note that if a result file still exists in the file system, and your Nix configuration has both <code>keep-outputs = true</code> and <code>keep-derivations = true</code>, all the dependencies used to build it will be kept. To see which result files prevent garbage collection, run:		Note that if a result file still exists in the file system, and your Nix configuration has both <code>keep-outputs = true</code> and <code>keep-derivations = true</code>, all the dependencies used to build it will be kept. To see which result files prevent garbage collection, run:

Pigs: Add category nixos and nix

2025-05-18T18:17:43Z

Add category nixos and nix

← Older revision		Revision as of 18:17, 18 May 2025
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	<references group="cf."/>		<references group="cf."/>

			[[Category:NixOS]]
			[[Category:Nix]]

Denperidge: Moving the store: fixed rsync --hard-links argument, merged rsync commands. Moved mount instructions from mounting on /mnt to mounting on /mnt/nix, added mount options

2024-10-05T17:08:05Z

Moving the store: fixed rsync --hard-links argument, merged rsync commands. Moved mount instructions from mounting on /mnt to mounting on /mnt/nix, added mount options

← Older revision		Revision as of 17:08, 5 October 2024
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	# Create a new partition		# Create a new partition
	# Mount this new partition over <code>/mnt</code> <syntaxhighlight lang="console">		# Mount this new partition over <code>/mnt</code> <syntaxhighlight lang="console">
	# mount /dev/disk/by-label/nix /mnt		# mount -o defaults,noatime /dev/disk/by-label/nix /mnt/nix
	</syntaxhighlight>		</syntaxhighlight>
	# Copy everything from <code>/nix</code> to <code>/mnt</code> ''Trailing slashes are important'', in that without them, <code>rsync</code> will create an additional directory of the same name at the destination. <syntaxhighlight lang="console">		# Copy everything from <code>/nix</code> to <code>/mnt</code> ''Trailing slashes are important'', in that without them, <code>rsync</code> will create an additional directory of the same name at the destination. <syntaxhighlight lang="console">
	# rsync --archive --~~hardlinks~~ --acls --one-file-system --verbose /nix/store/ /mnt~~/store~~		# rsync --archive --hard-links --acls --one-file-system --verbose /nix/{store,var} /mnt/nix
	~~# rsync --archive --hardlinks --acls --one-file-system --verbose~~ /nix~~/var/ /mnt/var~~
	</syntaxhighlight>		</syntaxhighlight>
	# Mount the new partition as the new <code>/nix</code> <syntaxhighlight lang="console">		# Mount the new partition as the new <code>/nix</code> <syntaxhighlight lang="console">
	# umount /mnt		# umount /mnt/nix
	# mount /dev/disk/by-label/nix /nix		# mount /dev/disk/by-label/nix /nix
	</syntaxhighlight>		</syntaxhighlight>

Adda0: Fix trailing typo.

2024-07-29T17:43:52Z

Fix trailing typo.

← Older revision		Revision as of 17:43, 29 July 2024
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	== Optimising the store ==		== Optimising the store ==
	Here we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.		Here, we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.
	r
	=== Automatic ===		=== Automatic ===
	To turn on periodic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:		To turn on periodic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:
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	Run		Run
	{{ic\|# nix-store --optimise}}.		{{ic\|# nix-store --optimise}}.
	This is a potentially long operation.		This is a potentially long operation.

	== Garbage collection ==		== Garbage collection ==

Mic92 at 14:17, 27 July 2024

2024-07-27T14:17:34Z

← Older revision		Revision as of 14:17, 27 July 2024
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	== Optimising the store ==		== Optimising the store ==
	Here we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.		Here we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.
			r
	=== Automatic ===		=== Automatic ===
	To turn on periodic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:		To turn on periodic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:
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	</syntaxhighlight>		</syntaxhighlight>
	# Copy everything from <code>/nix</code> to <code>/mnt</code> ''Trailing slashes are important'', in that without them, <code>rsync</code> will create an additional directory of the same name at the destination. <syntaxhighlight lang="console">		# Copy everything from <code>/nix</code> to <code>/mnt</code> ''Trailing slashes are important'', in that without them, <code>rsync</code> will create an additional directory of the same name at the destination. <syntaxhighlight lang="console">
	# rsync --archive --acls --one-file-system --verbose /nix/store/ /mnt/store		# rsync --archive --hardlinks --acls --one-file-system --verbose /nix/store/ /mnt/store
	# rsync --archive --acls --one-file-system --verbose /nix/var/ /mnt/var		# rsync --archive --hardlinks --acls --one-file-system --verbose /nix/var/ /mnt/var
	</syntaxhighlight>		</syntaxhighlight>
	# Mount the new partition as the new <code>/nix</code> <syntaxhighlight lang="console">		# Mount the new partition as the new <code>/nix</code> <syntaxhighlight lang="console">

imported>LucasWagler: Wording in Automatic Optimisation

2024-01-01T23:27:49Z

Wording in Automatic Optimisation

← Older revision		Revision as of 23:27, 1 January 2024
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	=== Automatic ===		=== Automatic ===
	To turn on ~~automatic~~ optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:		To turn on periodic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:
	{{file\|configuration.nix\|nix\|<nowiki>		{{file\|configuration.nix\|nix\|<nowiki>
	nix.optimise.automatic = true;		nix.optimise.automatic = true;
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	</nowiki>}}		</nowiki>}}

	Alternatively, the store can be optimised on ''every'' build. This may slow down builds, as discussed [https://github.com/NixOS/nix/issues/6033 here]. To enable this behavior, set the following option:		Alternatively, the store can be optimised during ''every'' build. This may slow down builds, as discussed [https://github.com/NixOS/nix/issues/6033 here]. To enable this behavior, set the following option:
	{{file\|configuration.nix\|nix\|<nowiki>		{{file\|configuration.nix\|nix\|<nowiki>
	nix.settings.auto-optimise-store = true;		nix.settings.auto-optimise-store = true;

imported>LucasWagler: Rework automatic optimisation to differentiate the two methods.

2024-01-01T23:21:26Z

Rework automatic optimisation to differentiate the two methods.

← Older revision		Revision as of 23:21, 1 January 2024
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	A recurring problem with NixOS is lack of space on <code>/</code>. Even if you only ~~ocasionally~~ use Nix, it is easy for <code>/nix/store</code> to grow beyond reasonable sizes. What follows are generic notes on how to reduce the growth of the ~~{{nix:~~store}}.		A recurring problem with NixOS is lack of space on <code>/</code>. Even if you only occasionally use Nix, it is easy for <code>/nix/store</code> to grow beyond reasonable sizes. What follows are generic notes on how to reduce the growth of the [[Nix store]].

	== Optimising the store ==		== Optimising the store ==
	Here we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.		Here we demonstrate how to configure <code>nix</code> to save space via hardlinking store files.

	==== Automatic ====		=== Automatic ===
	To turn on automatic optimisation ~~for newer derivations~~, ~~add~~ the following option to <code>/etc/nixos/configuration.nix</code>:		To turn on automatic optimisation of the nix store, set the following option in <code>/etc/nixos/configuration.nix</code>:
	{{file\|configuration.nix\|nix\|<nowiki>		{{file\|configuration.nix\|nix\|<nowiki>
	nix.optimise.automatic = true;		nix.optimise.automatic = true;
			nix.optimise.dates = [ "03:45" ]; # Optional; allows customizing optimisation schedule
	</nowiki>}}		</nowiki>}}

	~~{{Tip\|This option only applies to new files: so we recommend manually optimising your nix~~ store ~~in addition to this option~~.}}		Alternatively, the store can be optimised on ''every'' build. This may slow down builds, as discussed [https://github.com/NixOS/nix/issues/6033 here]. To enable this behavior, set the following option:
			{{file\|configuration.nix\|nix\|<nowiki>
			nix.settings.auto-optimise-store = true;
	~~The reason this option is not default to true automatically is~~ discussed ~~here:~~ https://github.com/NixOS/nix/issues/6033		</nowiki>}}

	~~Turning this~~ option ~~on (currently) means that it will try~~ to ~~optimize everytime you build~~, ~~further slowing builds and causing a lot of thrash. If you want to avoid~~ this~~, set up a simple cron job for weekly or just run every once in a while~~.		{{Tip\|This option only applies to new files, so we recommend manually optimising your nix store when first setting this option.}}

	==== Manual ====		=== Manual ===
	Run		Run
	{{ic\|# nix-store --optimise}}		{{ic\|# nix-store --optimise}}.
	This is a potentially long operation.		This is a potentially long operation.