Why '-c DEV' option for switch_root?

[Didier Kryn]

     Hi Laurent.

     I actually have a jffs2 filesystem on another part of the flash 
memory, but I decided not to use it for the purpose, for one reason: A 
single stupid bug might make the device non-bootable. Because, even if 
the jffs2 or squashfs is initially mounted read-only, the main reason to 
use it is the possibility to remount it read-write and modify it. You 
see the point? Better work hard in the beginning to work out a good 
stable initramfs which nobody can change/corrupt.

     With the initramfs, you restart always from a clean situation (once 
debugged of course). And the userland in my initramfs has a possibility 
to escape the normal sequence and start an interactive session, which 
allows to debug the environment.

     By the way, you wrote that initramfs is a trap. What is the trap, 
is it initramfs or the need for swhtch_root? Is it different if I 
switch_root from another filesystem?

     Didier

Le 16/12/2013 19:45, Laurent Bercot a écrit :
>
>> But about the usefullness of initramfs, I think you are wrong.
>>  I don't think I could do the job without it.
>
>  Hi Didier,
>
>  Eh, you could. You have some flash to boot the kernel from: you could
> as well have a small squashfs root filesystem on it with a script that
> performs all the initialization work you're currently performing in the
> initramfs.
>  Whether or not that's better or not than initramfs is debatable. I find
> it better - and I think that you'll find it simpler to maintain if you
> try it out - but I realize that my views about this are not shared by 
> many.
> The best approach, as always, is whatever works for you, your team, and
> your users.
>