linux-kernel - Re: [PATCH v10 0/2] dm: boot a mapped device without an initramfs

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Date:   Sat, 03 Nov 2018 10:10:08 +0100
From:   Richard Weinberger <richard@....at>
To:     Helen Koike <helen.koike@...labora.com>, keescook@...omium.org
Cc:     dm-devel@...hat.com, agk@...hat.com, snitzer@...hat.com,
        linux-kernel@...r.kernel.org, enric.balletbo@...labora.com,
        wad@...omium.org, linux-doc@...r.kernel.org, linux-lvm@...hat.com,
        kernel@...labora.com
Subject: Re: [PATCH v10 0/2] dm: boot a mapped device without an initramfs

Helen,

Am Samstag, 3. November 2018, 04:53:39 CET schrieb Helen Koike:
> As mentioned in the discussion from the previous version of this patch, Android
> and Chrome OS do not use initramfs mostly due to boot time and size liability.

Do you have numbers on that?

I understand that using something like dracut with systemd inside is not what you
want from a boot time point of view.
But having an initramfs embedded into the kernel image which contains only a single
static linked binary can be *very* small and fast.
If you invest a little more time, you don't even need a libc, just fire up some
syscalls to setup your dm. I use this technique regularly on deeply embedded systems
to setup non-trivial UBIFS/crypto stuff.

Want I'm trying to say, before adding ad-hoc a feature to the kernel, we should be
very sure that there is no other way to solve this in a sane manner.
We have initramfs support for reasons.

Thanks,
//richard