On 20/07/02 08:05AM, Benda Xu wrote:
> >> Could you please remind me why we need a bootstrap-init?  Can we just
> >> exec the Android init when the lxc-guest starts?
> >
> > Yeah sure. Apparently, Android needs to parse its device tree for early
> > mounting partitions, before exec'ing `init`. Plus even before dealing
> > with the dt, we need to mount `/system` and switch root to it.
> > I could create the environment for "using /system as root" w/o the help
> > of `bootstrap-init` but I couldn't deal with the device tree easily. 
> >
> > `bootstrap-init` creates the entire environment for android to boot from
> > scratch and then finally exec's `init`. So I proposed to use it instead
> > of manually setting up the LXC container for system-as-root devices. 
> > That way the setup is clean as we only need a /dev directory and a static
> > `bootstrap-init` binary inside of the LXC rootfs.
> 
> In principle you can choose your way of achieving things.  But
> considering you got stuck in making a functional 'bootstrap-init', I
> have 2 questions.

I would like to clarify first that bootstrap-init works fine, but due to
the nature of build-system it requires, I was having difficulties in
compiling it natively in arm64 Gentoo.
 
> 1. If you need to prepare a proper environment for Android to boot
>    inside the LXC guest, please check out LXC container hooks in
>    lxc.container.conf(5) manpage.  Another init seems an overkill for
>    me.

I was going with this approach initially, but the container configs just
don't seem apt for a process like this. I mean to mount the early
partitions only, I have no clue how I would approach parsing the device
tree using the LXC conf. 

Although I had made some slight edits to the original container hook
scripts, for keeping the rootfs clean after reboots and more. You could
check the modified scripts in [1].

> 2. Why bootstrap-init needs to be written in C++?  Would a shell script
>    enough?

I followed Magisk's approach of booting SAR Android. I thought of
rewriting the entire init but realised that that would be rather
inefficient. Therefore, I stripped all the "Magisk-y" code and put
forward the bare minimum required for functioning.
In theory, we could rewrite it all in shell, but then again, I would not
recommend it as it could be somewhat lengthy. 
Moreover, this setup is scalable and it could be extended later for any 
new boot-scheme Android pulls up.

If required by any situation, I can willingly rewrite it in shell as 
well.

Regards,
Gunwant

[1] https://wantguns.gitlab.io/blog/sharkbait/starting_android_in_gentoo/#install-lxc