Re: Way to switch easily (Was: Re: Egcs, gcc, and Debian)
On Aug 18, Galen Hazelwood wrote
> Jean Pierre LeJacq wrote:
>
> > This isn't scalable. Our situation here is that we require several
> > versions of packages like gcc available simultaneously. Different
> > users will use different versions.
> >
> > The current Debian /etc/alternatives approach doesn't work either.
> >
> > The solution I like the best is to use the /opt directory layout.
> >
> > /opt/gcc-2.7.0
> > /opt/gcc-2.7.2
>
> As I understand it, /opt is a ghetto for commercial packages which can't
> know in advance anything about the structure of the linux box they've
> been installed on. I don't think that's appropriate in this case.
That may be what many people portray it as, but I can tell you that it
can also be used *very effectively* as Jean Pierre suggests.
I use it on our Solaris boxes as a way to bring, for instance, a new
copy of perl on-line without disruption. You see, we have apps done
in perl that *must be running*, and yet depend on perl modules that
can only be installed after Perl is installed.
So, I can bring up the new perl (under /opt/perl-5.004_02) while the
existing one (/opt/perl-5.004) is still running. When I have
everything done on the new one, I change a symlink in /usr/bin or
/usr/local/bin, and everyone starts running the new one. After the
next time I reboot, I can zap the old installation.
Even Debian's package system doesn't give me this security, even if
I'm running dpkg by hand.
> I really don't see any good solution to this one. I'm going to
> release egcs with binaries "egcc", "eg++", etc., and those who want
> to change things can go into /usr/bin/ themselves and move things
> around.
Why not use the update-alternatives functionality?
People will be able to either use them under their installed names, or
use them as gcc, and all they need to do is change one symlink and run
update-alternatives to change back and forth. The only comments
against update-alternatives seem to stem from ignorance of how it
works.
Or maybe I'm the ignorant one---wouldn't be the first time.
Mike.
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