Custom image build shows stock buildhost and build time for kernel

I’m building a custom image to test a patch. However facing something a bit strange, my custom build looks a lot like the stock kernel.

root@bpi:~# cat /proc/version
Linux version 5.15.134 (builder@buildhost) (aarch64-openwrt-linux-musl-gcc (OpenWrt GCC 12.3.0 r23497-6637af95aa) 12.3.0, GNU ld (GNU Binutils) 2.40.0) #0 SMP Mon Oct 9 21:45:35 2023

I basically followed the guide at [https://openwrt.org/docs/guide-developer/toolchain/beginners-build-guide](https://Quick image building guide), downloaded the stock .config for my router and manually patched a couple of files. Then used the sysupgrade image/procedure to deploy.

  1. This is expected as OpenWRT does some reproducible build magic and sets a defined builder, buildhost and build time
    Or
  2. I messed up something and my router is using an old kernel

I unpacked the sysupgrade image and indeed file dates & times are all set at Mon Oct 9 21:45:35 2023 despite my build being done at a later date.

Releases are set to the release date from epoch.

cat ~/buildroot/openwrt/version.date

You can override this by setting your own build date from epoch date +%s > version.date.