[Bug 201486] [NEW] add boot argument to allow legacy change_root removal

[Jeremy Jackson]

Public bug reported:

Binary package hint: initramfs-tools

In Linux 2.6 the change_root method of invoking initrd is considered
"legacy", and might be removed in future.  The new method is pivot_root,
which does not have any special case code paths in kernel for initrd
after it's block device /dev/ram0 is created.  The kernel should be
booted "vmlinux root=/dev/ram0" which will mount the initrd, and execute
/sbin/init.

At present, this is problematic for initrd-tools (Gutsy), since there is
no way to specify the "real" root filesystem that is desired, without
using root= kernel commandline argument.

I propose a new argument be interpreted by initrd-tools /init script, to
allow migration to a fixed "root=/dev/ram0" on all kernels using initrd
to mount the real root device.  There is precedent with rdinit=,
although "rdroot=/dev/sda1" seems counterintuitive.  Alternatives should
be considered that are not confusing.  Perhaps root2=, realroot=, or
some other form.

Parsing the new argument could be conditional on finding
"root=/dev/ram0" in kernel commandline, to make things more precise.

** Affects: initramfs-tools (Ubuntu)
     Importance: Undecided
         Status: New

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add boot argument to allow legacy change_root removal 
https://bugs.launchpad.net/bugs/201486
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