Re: recommended way to find out whether one is "within" the initramfs?

[Christoph Anton Mitterer <calestyo@scientia.net>]

Hey Romain.

Thanks for your ideas:

On Wed, 2021-10-06 at 18:49 +0200, Romain Perier wrote:
> Quickly, few ideas (perhaps not the perfect ones):
> 1. Check for what is currently mounted as "/" ? (which technically
> should differ between initramfs or real rootfs)

That sounds like a pretty nice idea.
I guess for the iniramfs it would be always:
  none / rootfs
?
Or maybe the "none" could be anything in theory.


> 2. Check if your binaries are running inside a klibc or busybox
> context (both are supported via an initramfs) ?
> 3. Check if systemd is running ? (so you have started userspace
> processes part of your real rootfs)
> 

These two seem IMO a bit less "stable"... people might not use systemd
(at least in derivates) and checking for the binaries sounds a bit
ugly.



So maybe I do a combination and check for several indicators:
/scripts, /conf/initramfs.conf (which seems to be always there, update-
initramfs fails if the main initramfs.conf is missing or empty) and the
fs-type of the / fs.


Thanks,
Chris.