Protecting nix-shell dependencies from garbage collection?

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1

I have been looking for a way to keep packages used in my shell.nix from being garbage collected. Most online sources (1 2 3) point to using something along the lines of the following command:

nix-instantiate shell.nix --indirect --add-root ./.nix-gc-roots/shell.drv

and having keep-outputs = true in shell.nix, however I have not been able to get it to work. What I step I am missing?

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2

Direnv is the easiest that I know of with the additional benefit of it getting activated.
However be aware that aliases and functions in shellhooks don’t work automatically:
https://github.com/nix-community/nix-direnv/issues/245

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3

I am rather new to Nix and have not dipped my toes into flakes yet. My research leads me to believe that they aren’t necessary to accomplishing my goals, has that changed?

4

Direnv and shellhooks aren’t related to Flakes.
You can use shellhooks in a shell.nix file as well.

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5

Thanks for the tip! For most of my packages, direnv seems to be working. However, the following packages are still being garbage collected:

/nix/store/3mzd4jjvixjjkldnz3mjk7dpbjvl52hg-perl5.36.0-Any-URI-Escape-0.01
/nix/store/byb33msjlx9yaz603irlwkbzyj214bd6-perl5.36.0-YAML-PP-0.026
/nix/store/ihsm38jgs74qxpli4j7q6v1yv83zljq1-gcc-9.5.0-lib
/nix/store/ik9rhgnkagg9x9fb0hhhd3j0pacrcf66-kf5gpgmepp-16.08.3
/nix/store/jnc7klg39rdcravhm9f3jwg1xnfv81c0-xerces-c-3.2.4
/nix/store/pa7ad0v5hs8amap6j09dh72cwc36l0sv-python3-3.11.3
/nix/store/zayrihc2i9a2kl0mcmhqd9yn4xhc97ff-xsd-4.0.0
This is my shell.nix 
{ pkgs ? import <nixos> {} }: pkgs.mkShell {
	packages = with pkgs; [
		bison
		boost
		cmake
		curl
		cyrus_sasl
		docbook_xml_dtd_45
		docbook-xsl-ns
		flex
		gperf
		intltool
		libsForQt5.accounts-qt
		libsForQt5.kf5gpgmepp
		libsForQt5.phonon
		libsForQt5.qcoro
		libsForQt5.qgpgme
		libsForQt5.qtkeychain
		libsForQt5.signond
		libgcrypt
		libical
		perl
		perl536Packages.AnyURIEscape
		perl536Packages.IOSocketSSL
		perl536Packages.YAMLPP
		pkg-config
		polkit
		python311
		qrencode
		qt5.qtbase
		qt5.qtnetworkauth
		qt5.qttools
		qt5.qtquickcontrols2
		qt5.qtwayland
		qt5.qtwebengine
		qt5.qtxmlpatterns
		qt5.qtx11extras
		util-linux
		wayland
		wayland-protocols
		xapian
		xercesc
		xsd
		xorg.libXdmcp
		xz
	];
}

Is there any reason why it wouldn’t work for these?

6

I honestly don’t know and would’ve to test how it behaves on my machine but that would have to wait until after the weekend.

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