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add outputs.manifest for diagnosing image size problems

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This commit is contained in:
Daniel Barlow 2022-09-27 22:07:18 +01:00
parent 5e573cef09
commit 2e13f1372e
3 changed files with 22 additions and 3 deletions
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10
README.md
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@ -114,6 +114,16 @@ Assuming you have nixpkgs checked out in a peer directory of this one,
NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH ./run-tests.sh
## Diagnosing unexpectedly large images
Sometimes you can add a package and it causes the image size to balloon
because it has dependencies on other things you didn't know about. Build the
`outputs.manifest` attribute, which is a json representation of the
filesystem, and you can run `nix-store --query` on it:
NIX_PATH=nixpkgs=../nixpkgs:$NIX_PATH NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nix-build -I liminix-config=path/to/your/configuration.nix --arg device "import ./devices/qemu.nix" -A outputs.manifest -o manifest
nix-store -q --tree manifest
## Articles of interest

10
THOUGHTS.txt
View file

@ -186,7 +186,7 @@ creates the interface instead of using an existing unconfigured one
5) write a test for udhcp
6) squashfs size is ~ 14MB for a configuration with not much in it,
DONE 6) squashfs size is ~ 14MB for a configuration with not much in it,
look for obvious wastes of space
7) some of the pppoe config should be moved into a ppp service
@ -207,7 +207,13 @@ is that specified or fluke?
19) syslogd - use busybox or s6?
20) The option currently called defaultPackages needs a better name as
DONE 20) The option currently called defaultPackages needs a better name as
it doesn't have the same semantics as nixos
environment.defaultPackages. maybe call it packagesInProfile or
packagesOnPath. or defaultProfile.packages
Tue Sep 27 22:00:36 BST 2022
Found the cause of huge image size: rp-pppoe ships with scripts that
reference build-time packages, so we have x86-64 glibc in there

5
default.nix
View file

@ -4,7 +4,7 @@
let
overlay = import ./overlay.nix;
nixpkgs = import <nixpkgs> ( device.system // {overlays = [overlay]; });
inherit (nixpkgs.pkgs) callPackage liminix;
inherit (nixpkgs.pkgs) callPackage writeText liminix;
config = (import ./merge-modules.nix) [
./modules/base.nix
({ lib, ... } : { config = { inherit (device) kernel; }; })
@ -24,6 +24,9 @@ in {
ln -s ${squashfs} squashfs
ln -s ${kernel.vmlinux} vmlinux
'';
# this exists so that you can run "nix-store -q --tree" on it and find
# out what's in the image, which is nice if it's unexpectedly huge
manifest = writeText "manifest.json" (builtins.toJSON config.filesystem.contents);
};
# this is just here as a convenience, so that we can get a
# cross-compiling nix-shell for any package we're customizing