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    SubjectRe: udev and devfs - The final word
    Linus, what Andries is saying is that if you export a directory (say
    /home) the process of exporting it somehow uses the /dev device number so
    if the server reboots and gets a different device number for the partition
    that /home is on the clients won't see it as the same export, breaking the
    NFS requirement that a server can be rebooted.

    I don't agree with him becouse if the NFS server does include /dev info in
    what it shows to the outside world it's already broken.

    David Lang


    On Sun, 4 Jan 2004, Linus Torvalds wrote:

    > Date: Sun, 4 Jan 2004 18:52:56 -0800 (PST)
    > From: Linus Torvalds <torvalds@osdl.org>
    > To: Andries Brouwer <aebr@win.tue.nl>
    > Cc: Rob Love <rml@ximian.com>, rob@landley.net,
    > Pascal Schmidt <der.eremit@email.de>, linux-kernel@vger.kernel.org,
    > Greg KH <greg@kroah.com>
    > Subject: Re: udev and devfs - The final word
    >
    >
    >
    > On Sun, 4 Jan 2004, Andries Brouwer wrote:
    > >
    > > Surprise! Are you leaving POSIX? Or ditching NFS?
    > > Or demanding that NFS servers must never reboot?
    >
    > Ok, Andries, time for you to take a deep breath, and calm down. Because
    > your arguments are getting ridiculous in the extreme.
    >
    > A NFS server is sure as hell not going to export _its_ dynamic /dev to its
    > clients. That would be not just stupid, but crazy. Next you tell me that
    > you were using devfs and exporting that over NFS.
    >
    > A NFS server is going to export something _totally_ different than its own
    > /dev directory - it needs to be _client_-specific anyway. That's true with
    > stable numbers too, btw - ever tried to mount a Solaris /dev on a Linux
    > client? No workee.
    >
    > > A common Unix idiom is testing for the identity
    > > of two files by comparing st_ino and st_dev.
    > > A broken idiom?
    >
    > No. It still works. Even if the device numbers change across reboots.
    >
    > Why? Becuase that _program_ sure as hell isn't running across a reboot.
    >
    > And again, this is not something we haven't seen before. Have you ever
    > looked at the "st_dev" values? Try once - look at what it returns for a
    > NFS-mounted filesystem. Ponder. Notice how it already is NOT stable across
    > reboots.
    >
    > In other words, the stuff you're complaining about is all stuff that
    > nobody has _ever_ been able to rely on, and that has nothign to do with
    > udev or anythign else. It all just shows how 100% right I am for saying
    > that you cannot rely on stable numbers.
    >
    > So I repeat: calm down, and think it through.
    >
    > Linus
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