nixos/iso-image: make squashfs compression easily configurable #94660
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worldofpeace
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Aug 4, 2020
xaverdh
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Motivation for this change
(Re)building the ISO image currently takes ~7min on a modern system, mostly due to
squashfscompression of the store.Using
zstdat level 6 instead ofxzdrops this to ~1 minute (at the cost of a somewhat increased size obviously). This is quite relevant, e.g. if you find yourself repeatedly buildingisoimages with small changes.While in theory the compression is already configurable in
nixos/lib/make-squashfs.nix,iso-image.nixdoes not pass this option through in a friendly manner. Change this, so people who prefer fast build times over size can just set:isoImage.squashfsCompression = "zstd -Xcompression-level 6"This is not my personal motivation, but some people may also choose e.g.
zstdfor faster decompression.Things done
Checked that the iso image still builds with these changes as well as with
zstdcompression set as hinted above.