Re: A "magical" HDD formatting question.
Your objective is:
> I have to do so because it is impossible for now to boot from CD/USB.
> And I want to move from ext3 to ext4.
Although pivot_root etc. may be used but that is too fancy...
If I were you, I do the following:
1. boot from internal HDD
2. mount externel HDD and copy your local system there.
3. adjust few parameters in thet copied system so it is bootable and
4. make your boot loader like grub to boot externel HDD.
5. reboot to externel HDD.
6. partition and format internal HDD.
7. install fresh system to internal HDD using debootstrap etc.
But I really think you have independent way to boot system. You may
make mistake and then you need to have ways to recover.
Anyway, save your personal data first.