Update to kernel v5.10.84 to fix Docker overlay bugs
It seems that Alpine v3.14 and v3.15 use Linux kernel 5.10.47:
$ docker run -it docker.io/library/alpine:3.14.2 sh / # uname -a Linux f678a560a9eb 5.10.47-linuxkit #1 SMP Sat Jul 3 21:51:47 UTC 2021 x86_64 Linux
As explained in https://github.com/docker/for-linux/issues/1015, there is a significant bug in the kernel with the overlay filesystem that can result in 0-byte files created when using Docker.
Linux 5.10.84 fixes this problem, and I highly recommend upgrading ASAP.