Why '-c DEV' option for switch_root?

[Lauri Kasanen]

On Mon, Dec 16, 2013, at 10:05, Laurent Bercot wrote:
> On 2013-12-16 01:08, Rob Landley wrote:
> > The most recent kernel has my initmpfs patches, meaning initramfs
> >  can now be a tmpfs instead of ramfs.
> > [snip blurb]
> 
>   You're listing reasons why initramfs (or initmpfs, if you prefer) is
> more logical than it was before, more convenient, etc. All this may be
> true, but it does not mean initramfs is actually *useful*.
> 
>   I have yet to see a case where initramfs is really needed. Every time
> I've seen a system boot on initramfs, the same goals could have been
> achieved via booting on the real root filesystem and doing work during
> initialization, which implies a lot less code, and is more maintainable,
> and safer (if something fails early on).

I disagree, initramfs (and now enhanced upstream with tmpfs) is very
useful for running in RAM without additional steps. There may not be a
"real root", maybe we booted via PXE or an unsupported SCSI controller,
etc.

Without initramfs you'd have hacks like initrd -> switch to tmpfs ->
more code, more complexity. Without initrd either you'd have even worse
hacks with the kernel itself.

- Lauri

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