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sd-image: Slims the ext4 filesystem even more. 

This is to try and squeeze more lost space from the image, so that hydra
starts building it again.

The fsck previous to the resize2fs is required so resize2fs works.

The one afterwards is a sanity check.

Using `-M` from resize2fs will not give much saved space due to a known
(in the manual) issue.

```
[samueldr@aarch64:~/nixpkgs]$ ls -lh result-*/*/*.img
-r--r--r-- 1 root root 2.2G Jan  1  1970 result-original/sd-image/nixos-sd-image-18.09.git.a7fd431-aarch64-linux.img
-r--r--r-- 1 root root 2.1G Jan  1  1970 result-M/sd-image/nixos-sd-image-18.09.git.a7fd431-aarch64-linux.img
-r--r--r-- 1 root root 1.9G Jan  1  1970 result-slimmed/sd-image/nixos-sd-image-18.09.git.a7fd431-aarch64-linux.img
```

```
[samueldr@aarch64:~/nixpkgs]$ nix path-info -S ./result-original
/nix/store/c8k9n78gylx293rjh762fr05a069kxp2-nixos-sd-image-18.09.git.a7fd431-aarch64-linux.img   3844125000

[samueldr@aarch64:~/nixpkgs]$ nix path-info -S ./result-slimmed
/nix/store/962238skj5mnzhrsmjy23dyzmxk77sp4-nixos-sd-image-18.09.git.a7fd431-aarch64-linux.img   3447473208
```
This commit is contained in:
Samuel Dionne-Riel 2018-11-28 22:10:15 -05:00
parent 80738ed9dc
commit 61bdaad9a9
1 changed files with 19 additions and 0 deletions
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19
nixos/lib/make-ext4-fs.nix
View File

@ -94,5 +94,24 @@ pkgs.stdenv.mkDerivation {
cat errorlog
return 1
fi
(
# Resizes **snugly** to its actual limits (or closer to)
free=$(dumpe2fs $out | grep '^Free blocks:')
blocksize=$(dumpe2fs $out | grep '^Block size:')
blocks=$(dumpe2fs $out | grep '^Block count:')
blocks=$((''${blocks##*:})) # format the number.
blocksize=$((''${blocksize##*:})) # format the number.
# System can't boot with 0 blocks free.
# Add 16MiB of free space
fudge=$(( 16 * 1024 * 1024 / blocksize ))
size=$(( blocks - ''${free##*:} + fudge ))
echo "Resizing from $blocks blocks to $size blocks. (~ $((size*blocksize/1024/1024))MiB)"
EXT2FS_NO_MTAB_OK=yes resize2fs $out -f $size
)
# And a final fsck, because of the previous truncating.
fsck.ext4 -n -f $out
'';
}