RFC: Kill off addRamDisk

[Olaf Hering]

 On Mon, Aug 01, David Gibson wrote:

> > Can the $O/usr/initramfs_data.cpio.gz file linked later into the vmlinux
> > file? I see an '.init.ramfs' section there, perhaps you want to replace
> > the addRamdisk binary with an addRamdisk shell script which calls
> > objcopy. But this way we lose the overlay feature.
> 
> I'm not sure what you mean by "the overlay feature".

The initrd content passed via the bootloader is extracted over the
in-kernel cpio image.
initramfs_data.cpio.gz contains per default /dev, /dev/console and
/root. Thats enough to run udevstart to fill /dev with other required
/sys/class/{mem,tty}/ device nodes. Maybe it will work also with an empty
rootfs, if nothing fails when the stdin/stdout device node is missing.

> > A simple 'find . | cpio -H newc --create | gzip -9 > tmp_initrd.gz'
> > would not work anymore as unprivileged user because mknod cant be done
> > that way.
> 
> How does the method used to combine the vmlinux and initrd have any
> bearing on what we can do when generating the initrd?

an user process cant run 'mknod ./dev/console'. I see a panic() in
init/main.c if /dev/console is missing.