Re: Could swap space be shared among different linux distributions?

From: Nico Kadel-Garcia (nkadel_at_comcast.net)
Date: 08/23/05

  • Next message: Paul Colquhoun: "Re: Could swap space be shared among different linux distributions?" 
    Date: Tue, 23 Aug 2005 06:42:27 -0400

    "Peter T. Breuer" <ptb@oboe.it.uc3m.es> wrote in message
    news:95uqt2-s12.ln1@news.it.uc3m.es...
    > Bruce <liubaoliang@gmail.com> wrote:
    >> Is there any way to share /home /var /dev fold between these
    >> distributions?
    >
    > Sure. Every way. What's the problem?
    >
    >> I thought there should be no way.
    >
    > Why would you think that? What happened when you DID it? All you would
    > THINK you would get is mixed up log files and so on, but if that's OK
    > with you, that's OK with you. And you might get unsuited defaults set
    > in your home dir config files, but that's not so likely.

    Oh for cripes sake, ignore Peter. He loves to flaunt his teeny bits of
    knowledge as superior moral values that he's just too cool to tell you, and
    lift his uppity nose at newbies. He's the absolute worst type of Linux geek.

    /dev is where the "devices" go, such as /dev/hda for your first IDE hard
    drive, /dev/hda1 for the first partition on it, /dev/hda2 for the second
    partition, etc. The problem is that different kernels and software setups
    can have slightly different layouts for these things. For example, old Linux
    kernels ususally used /dev/cuaa0 for the first serial port. Current kernels
    use /dev/ttyS0, and trying to manage two such different sets of files in the
    same setup can be an adventure. But /dev/ is small: you don't gain much by
    folding it up this way.

    /var.... is another story. Again, different distributions will have *WILDLY*
    different layouts of material there. For example, if you run RedHat bind
    with chroot enabled, your DNS configuration file is in
    /var/named/chroot/etc/named.conf, with a symlink to it at /etc/named.conf.
    SuSe does it backwards, and flat-out wrong, with the real file at
    /etc/named.conf and symlink to it at /var/named/etc/named.conf. (You should
    never use symlinks from inside a chroot cage to outside it. *NEVER*.) And
    ownership of files will be inconsistent. Web materials for the Apache user
    from one user may not match the "uid" of the httpd user from another
    distribution, but they may both keep their CGI tools at /var/www/cgi-biin.
    Inconsistent ownership will cause serious webserver problems, and adding or
    deleting tools from one distribution may replace those of another.

    Don't do that unless you need to. If you need to, consider sharing a
    separate partition (such as /var-shared) and running symlinks for those
    particular big chunks of stuff that you might want to share (such as, say,
    /var/www/test-web-site).

    > And /dev is usually not a disk partition! It's a fake kernel file
    > system, so there is no need to share it. There wouldn't be any sense in
    > sharing it anyway, since it is never a disk partition of its own even
    > when it is on disk , and it takes up no noticable space in its own
    > right.

    /dev is a directory that contains files, in this case block devices (which
    are also a kind of file in the deep guts of how UNIX and Linux work).
    Nothing fake about it. But some bits of it need to be there, such as
    /dev/hda1, to mount or remount the root partition, so having it on a
    separate partition is just asking for grief and instability. There are
    *bits* of it, such as /dev/shm, that are kernel tricks and that get mounted
    as separate partitions, much like /proc.

    > Now, sharing /proc WOULD be a good idea! :-).

    And for the newbies, Peter is trying to be vaguely funny and failing, /proc
    *IS* a kernel trick that provides hooks to read to or from the kernel. It's
    not actually local disk, and sharing it makes no sense whatsoever since it's
    entirely a kernel information hook.

  • Next message: Paul Colquhoun: "Re: Could swap space be shared among different linux distributions?"

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