Re: [tlug] Upgrading the kernel...?

["Stephen J. Turnbull" <stephen@example.com>]

>>>>> "Dave" == Dave M G <Dave> writes:

    Dave> First, isn't 2.6.17 waaayyyy over on the bleeding edge? I've
    Dave> seen talk of 2.6.16, but this is the first time I've heard
    Dave> of 2.6.17.

No.  First, let's talk about the traditional Linux kernel version
numbering.  I'm not sure what the criterion for major numbering is (#
of Torvalds children?  floor(sqrt(FreeBSD major version))), but if the
major version changes, you're looking at replacing the whole system.
However, it's been "2" since 1997 or so, so I wouldn't worry about it.

The minor version (the "6" in "2.6") tells you about changes in
internal APIs, things like udev or (much older) the proc filesystem.
Minor versions come in two flavors, "odd" (as in, "that's odd, I've
never seen a 'pink screen' kernel oops before") and "even" (as in
"even keel").  There are constraints on what Linus will permit himself
in the odd series, but you should not bet a business on it.  However,
the even series are intended for bugfixes and extensions.  The reason
that extensions are permitted is that you couldn't use them before, so
you can't hurt yourself (in theory) if you refuse to use them now,
because the internal APIs aren't permitted to change within the same
minor version series.

By contrast, "2.7" is the bleeding edge.

The micro version (the "17" in "2.6.17") tells you that bugs have been
fixed and extensions (eg, new drivers added).  "2.6.17" vs. "2.6.18"
is unlikely to give your system even a second of indigestion.

Recently (with the 2.6 series?) a "nano" version has been added.
These are guaranteed to include bugfixes only, I suspect.

    Dave> Second, people in the bug report talk about upgrading Ubuntu
    Dave> Dapper to 2.6.17 like it's no big deal. But I don't get
    Dave> it... aren't a whole bunch of drivers and stuff going to
    Dave> crap out on me?

No.  Those drivers that are build into the kernel are, well, built
into the kernel and will therefore have to be replaced by the version
that comes with the new kernel.  The drivers that are loadable modules
are stored on disk according to kernel version.  If you do "ls
/lib/modules" you will see a list of subdirectories that look like
kernel versions.  That's because they are!

    Dave> I mean, there's a fundamental I don't understand about
    Dave> this. I thought Ubuntu Dapper and a 2.6.15 kernel were bound
    Dave> together. Is it still "Dapper" if I change my kernel?

Yes.  You could use a 1.0 kernel and (to the extent that things
continued to work, which mostly they wouldn't :-) it would still be
recognizably Dapper and not Debian "sid" or Gentoo or FC5.  The Linux
kernel is an amazing accomplishment, and Linus is a certifiable
genius.  Nevertheless, the system around it, including the GNU System
proper as well as the parts that they've shamelessly OEM'ed as "part
of the GNU System" (TeX, perl, Ghostscript, X11, GTK+, GNOME, etc) is
bigger, and entirely responsible for the "look and feel" (only a few
truly WiReD geeks ever talk directly to a kernel).

The reason is this acronym "API" (application programming interface)
that comes up a lot.  Simply put, the API is a set of names for *what
should be done*.  The programs are various implementations, which may
differ internally but should do the same thing.  In open source,
because everybody does their own thing, we all agree on a large number
of APIs to describe the interfaces between our programs.  Because the
APIs don't change within a minor version, you can expect that working
programs will continue to work.

    Dave> Third, aren't I probably going to simply be changing
    Dave> headaches?

"Possibly", yes.  "Probably", no.

    Dave> It was kind of like this before when I went from Fedora to
    Dave> CentOS to Ubuntu. Each one did some things better than the
    Dave> other, but some things worse.

With a few exceptions, that will not be true of the kernel upgrade at
the micro or nano version level.  Things will just get better.  The
upgrade itself is potentially trouble, but once you succeed in doing
that, you will notice very few changes, except that a few things work
better than before.

But I have a date with my daughter ... see ya later. :-)


-- 
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