linux-kernel - Re: Mounting NFS root FS

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Date:	Sat, 2 Dec 2006 23:55:28 +0100
From:	Willy Tarreau <w@....eu>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	William Estrada <MrUmunhum@...dial.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Mounting NFS root FS

On Sat, Dec 02, 2006 at 10:56:38PM +0100, Jan Engelhardt wrote:
> 
> >> > I have been trying to make FC5's kernel do a boot with an NFS root file
> >> > system.  I see
> >> > the support is in the kernel(?).  I have tried this:
> >> >
> >> >> root=/dev/nfs nfsroot=10.1.1.12:/tftpboot/NFS/Root_FS
> >> 
> >> This feature is almost deprecated. One is supposed to use initramfs,
> >> /sbin/ip or some DHCP client, and a mount program nowadays.
> >
> >But I think that there are plenty of light terminals still booting like
> >this which will not be able to upgrade anymore then. Even right here,
> >my web server (parisc) boot from the network that way. At least an
> >initramfs would need to be able to cope with the same syntax,
> 
> No problem:
> 
> <<</init<<<
> #!/bin/bash
> 
> for o in `cat /proc/cmdline`; do
>     case "$o" in
>         nfsroot=*)
>             arg="${o##nfsroot=}";
>             ;;
>     esac;
> done;
> 
> ### further parse $arg
> >>>
> 
> simplified example of how this can be accomplished. This is why
> initrds/initramfs are so much more powerful than in-kernel software.

I'm not saying initramfs is not powerful, and indeed your example is
the common way of parsing cmdline for me too. What I'm saying is that
before nfsroot stops being supported, we'll need a working replacement
(and not "### further parse $arg"), if possible within the kernel tree
so that people who used to build kernels to boot such machines will
still be able to build kernels for them, even if this implies using
an initramfs with some tools in it.

The real danger of removing support for in-kernel features like this
is to leave people with no solution at all (because they don't know
how to proceed), and their workarounds are often worse than the
problem that we tried to fix in the first place.

Willy

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