Steve Litt <slitt@???> writes:

[...]

> If / is formatted ext4, it can be mounted directly by a kernel with ext4
> drivers, no initramfs needed.

The only reason why 'initramfs' is ever needed is because the kernel can
mount the 'real' root filesystem without loading a/ some additional
files first. This is a problem one typically encounters when building 'a
distribution kernel' because that must principally be ready to support
any conceivable hardware combination it could support. Hence, it's
usually configured such that all available anythings are built as
modules. But now, the kernel can't boot on any hardware because it
doesn't have the mass storage device driver for accessing / available
and doesn't know how to handle any kind of filesystem. Hence, all the
kernel modules together with the userspace software for loading modules
on demand are bundled into a second file also loaded by the boot loader
which eiter contains a filesystem the kernel can mount ('initrd') or an
archive file with all the files and related meta-information enabling
construction of a 'live' file system (initramfs).

For a real deployment, this is usually just humbug and can be replaced
with a kernel containing the drivers necessary for mounting a root
filesystem.