nixos/make-ext4-fs: increase fudge factor from 1.03 to 1.10 #91214
Conversation
Turns out, on smaller images (~800MiB uncompressed sdcard image size), the current fudge factor is way too small to even get the system to the phase where it can resize itself. I first tried with 1.05, but it wasn't enough.
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I’ve noticed this too. The smaller the system is, the larger fudge factor you need. I wish we could get rid of the fudge factor altogether. I think it might be better as a constant reserved space instead of a multiplier. /cc @samueldr |
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We probably need a fixed offset, and a factor - but I assume it also depends on the type/amount of files you add. It's a bummer we can't just ask for the real size it needs to get some space. I'm not really in favour of making the formula more complicated, by adding more empirically determined numbers, but I'm also not sure if there's any upper limits we're almost hitting, for which we need to be that conservative. |
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I believe the actual solution would be to make use of a tool that is made to create a filesystem with a tool that is better suited for the task of making a filesystem with predefined contents. This, in turn, does not need fudge factor. It knows about ext4 in intricate levels enough that it builds the filesystem from the inside out, finishing with the structures, leaving enough free space so things just work. (If you're a specific individual whom I shared a fudge factor thing with yesterday, using So, for this PR, I 👍 it, it's okay for now to bump up the fudge factor, but anything more involved should prefer switching to a tool made for the task, which in addition brings us reproducible filesystem images for free. |
This contains two more PRs currently staged for nixpkgs: - nixos/make-ext4-fs: increase fudge factor from 1.03 to 1.10 NixOS/nixpkgs#91214 - extlinux-conf-builder: allow a custom FDT to be specified NixOS/nixpkgs#91195 The former one is needed to have the initial sd image be big enough to be able to resize itself, the latter to circumvent u-boot not properly detecting our board, and trying to load the wrong FDT.
Turns out, on smaller images (~800MiB uncompressed sdcard image size),
the current fudge factor is way too small to even get the system to the
phase where it can resize itself.
I first tried with 1.05, but it wasn't enough.
Motivation for this change
Things done
sandboxinnix.confon non-NixOS linux)nix-shell -p nixpkgs-review --run "nixpkgs-review wip"./result/bin/)nix path-info -Sbefore and after)cc @NixOS/exotic-platform-maintainers