Re: [PATCH] initramfs: Allow rootfs to use tmpfs instead of ramfs

From: H. Peter Anvin
Date: Sun Jul 30 2006 - 14:47:43 EST

Hugh Dickins wrote:
On Sun, 30 Jul 2006, Al Boldi wrote:
Replugs rootfs to use tmpfs instead of ramfs as a Kconfig option.

Why? Looking further down we see what you should have explained here:
+ This option switches rootfs so that it uses tmpfs rather than ramfs
+ for its file storage. This makes rootfs swappable so having a large
+ initrd or initramfs image won't eat up valuable RAM.

Now, I'm far from an expert on initramfs and early userspace, but my
understanding is that the "init" of a (properly designed) initramfs
would pretty much "rm -rf" everything in the initramfs before passing
control to the final "init". So (almost?) no valuable RAM is eaten
up, nor the less valuable swap if you do extend this to tmpfs (unless
something gets left open, which I think should not be the case).

So I'm inclined to say that this patch is simply unnecessary. But
if people who know better think it's a good thing, I've no objection
(though I've not tried it): the Kconfiggery looks more likely to
provoke argument than the tmpfs/ramfs mods.


There is some justification: embedded people would like to load inittmpfs and then continue running.

The main issue -- which I am not sure what effect this patch has -- is that we would really like to move initramfs initialization even earlier in the kernel, so that it can include firmware loading for built-in device drivers, for example.

Thus, if this patch makes it harder to push initramfs initialization earlier, it's probably a bad thing. If not, the author of the patch really needs to explain why it works and why it doesn't add new dependencies to the initialization order.

Saying "this is a trivial patch" and pushing it on the -stable tree doesn't inspire too much confidence, as initialization is subtle.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at