linux-kernel - Re: [bug] /etc/profile: line 30: /dev/null: Permission denied (Was: Re: [PATCH] Remove broken by design and by implementation devtmpfs maintenance disaster)

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Date:	Thu, 17 Sep 2009 22:58:44 -0700
From:	Greg KH <greg@...ah.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Kay Sievers <kay.sievers@...y.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [bug] /etc/profile: line 30: /dev/null: Permission denied
	(Was: Re: [PATCH] Remove broken by design and by implementation
	devtmpfs maintenance disaster)

On Thu, Sep 17, 2009 at 10:31:13PM +0200, Ingo Molnar wrote:
> 
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > On Thu, 17 Sep 2009, Kay Sievers wrote:
> > 
> > > On Thu, Sep 17, 2009 at 20:53, Ingo Molnar <mingo@...e.hu> wrote:
> > > > I've reproduced a bug with the following .config options:
> > > >
> > > > ??CONFIG_DEVTMPFS=y
> > > > ??CONFIG_DEVTMPFS_MOUNT=y
> > > >
> > > > /dev/null and /dev/zero are not read/writable to ordinary users, 
> > > > breaking normal bootup and login:
> > > 
> > > Udev should run long before some ordinary/non-root user can login, 
> > > and apply the permissions as it always does. It's known to work on 
> > > Fedora, SUSE, Ubuntu. What kind of system/environment/setup is that 
> > > where you see this?
> > 
> > I don't know if this is what Ingo does, but I have a few machines 
> > where I don't run the distro-supplied 'initrd' at all, because it's 
> > easier to boot without it. The Fedora initrd doesn't allow me to 
> > sanely set root filesystem parameters without totally rewriting the 
> > initrd image, which I'm not interested in, for example (they'll take 
> > effect for the root initrd, not the final root).
> 
> Correct: i'm booting raw bzImages, with /dev copied to the real /dev. To 
> this box udev is mostly an annoyance that slows down my bootup ;-)

I use non-initrd systems as well, and this option works for me on Gentoo
and SUSE machines.

As you are using a very old udev, and the boot infrastructure for udev
in older Fedora releases was a bit "odd" in places, I would recommend
not using these options on that machine.  If we need to reword the
Kconfig help option to make it a bit more clear, do you have a
suggestion on what we should change?

> Furthermore, this is a really old image, Fedora Core 6, where udev does 
> not get updated anymore. I still boot new kernels on it though, and it 
> worked fine up to now.

It should continue to work if you don't select this option, right?  The
default is "N" :)

thanks,

greg k-h
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