The Kernel Newbie Corner: “initrd” and “initramfs”–Some Unfinished Business

“So What Do We Know So Far?

“Let’s recap what we discussed last week, just to set the
stage:

* Both the initramfs and initrd features are examples of what
are called “early userspace,” which gives us the opportunity to
create minimal root filesystems with enough kernel modules to allow
the boot process to continue, to the point where the kernel can
eventually mount the real root filesystem.

* To clarify the terminology, I use the phrase “initramfs” to
describe the root filesystem that is internal to the kernel, while
“initrd” is used to refer to the external root filesystem
represented by the “initrd” files in the /boot directory, and which
is passed to the booting kernel by the bootloader.

* The initrd files used to be a filesystem format so they needed
to be mounted in order to examine their contents. These days,
they’re almost always gzipped cpio-format files so, with the right
permissions, you can uncompress them and examine their contents
more conveniently.”

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