[Beowulf] [AMD64] Gentoo or Fedora

[Michael Jinks]

On Fri, Aug 31, 2007 at 01:28:43PM -0400, Mark Hahn wrote:
> >track down -- that it's not precisely correct to think of Gentoo as a
> >distribution.  Rather, it's a set of tools and a software index which
> >provide the opportunity to create one's own distribution.  The article
> 
> I'm being pedantic, I know, but I would disagree.  whether you build,
> configure, assemble it yourself does not really make it your distro.
> the distro, to me, is defined by the set of overall config choices - 
> does it use sysv-type init scripts, does it use /etc/defaults or sysconfig?

I agree that the difference between /etc/defaults, /etc/sysconfig, and
/etc/conf.d matters almost not at all to me, so long as I can remember
where I need to look on a particular system.  It's all got to go
someplace...

> what major version of glibc/etc does it use?

On my laptop, I'm using glibc-2.5, because that's the default for this
release of Gentoo.  If I wanted to change that, I have the option of
going back as far as 2.2.5, or forward up to 2.6.1.  Or, I could install
multiple versions side-by-side, if some package required a different
version but I didn't feel like rebuilding the whole system.  I've also
used Gentoo on embedded systems that replaced glibc with ulibc.

Would running multiple versions of glibc be painless?  I don't know,
I'm not eager to try it where something as fundamental as glibc is
concerned, but at least the possibility is accounted for.  I can say
first-hand that running multiple releases of Sun's JDK or Berkeley DB
is a well-supported proposition; so much so that at first I didn't
realize I was doing it.  Package dependencies were just taken care of at
install time.

> so centos isn't really 
> a distro, just a version or RHEL.  similarly, taking a RH-ish install
> and recompiling everything from SRPM doesn't really change the status 
> either...

I'm not specifically interested in the question of what is or is not a
"distribution"; rather, that language is useful to the extent that it
describes how Gentoo is qualitatively different from most other efforts
to simplify the process of creating a usable system.  If Gentoo just
forced the user to do the equivalent of building from SRPMs, that
wouldn't be much of a distinction, and I'd still be using Red Hat for
everything.  For me, the most important difference is not that Gentoo
makes it possible to replace large hunks of the system -- it's always
possible, even on "proprietary" Unix, if you know what you're doing --
but that they do as much as they can to make it easy.  Yes, Gentoo does
foist some choices onto the user.  They reinvented the SysV init
structure, for example.  But the "meta-ness" refers to the fact that
Gentoo is less a specific collection of packages and more a defined
strategy for automating system builds.

> >to (potentially very many) similar systems.  For some large networks,
> >the advantages that Gentoo allows in terms of control and system usage
> 
> I'm curious to hear the advantages.  I assume, for instance, that most
> installation will run customized kernels, rather than the distro one,
> but wouldn't normally recompile basic tools like 'ls' (but over time 
> might well have their own gcc, openssh, etc)

Maybe I shouldn't have used that word "advantage", since fine control
over the system isn't what all users need, and a lot of people aren't
ever going to care about departing from (say) their distributor's choice
of gcc version.  But Gentoo's approach means that if you do want to
replace gcc, rebuilding the whole system to account for a changed ABI is
an automated process instead of a manual one.  If you want to use gcc-3
for some things and gcc-4 for others, that's possible too, without
sacrificing package management.

More often, I'll find that some package needs a particular build-time
option in an upstream dependency.  Red Hat accounts for that by building
everything "Christmas tree"-style, with support for every DBMS and
graphics library switched on in every package where they matter.  On
Gentoo, it's possible to take that approach, but it's also easy to be
more minimalistic.  If I realize later that I should have had some
compile-time option switched on, I can change one file under /etc (with
the option of making the change global to the system, or specific to a
particular package and any of its dependencies), and then tell Portage
to rebuild whatever needs rebuilding while I go get coffee.

Since it's come up: while I was initially drawn to Gentoo partially
because of claims of boosted performance due to optimized builds, I never
got around to investigating the claims, and my subjective experience has
been that, if Gentoo builds a faster box than Red Hat (or Mandriva), the
differences aren't especially noticeable.  Disk I/O is disk I/O...  What
keeps me on Gentoo is a packaging structure that provides more
flexibility than I've seen anywhere else, and which wouldn't be possible
if the distributors didn't assume that the user had the option of
building everything from scratch.

-j