After configuring and building the kernel using make, why don't I have
initrd-<version>.img, but only got a huge
vmlinux binary (~150MB)?
The compressed images are under
If you still don't have the image, check if
Also, the kernel config allows you to choose the compression method, so the actual file name and compression algorithm may differ if you changed that kernel setting.
As others already mentioned, initrds are not generated by the linux compilation process, but by other tools. Note that unless, for some reason, you need external files (e.g. you need modules or udev to identify or mount