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Re: Red Hat user shopping around



On Thu, May 09, 2002 at 01:09:42AM -0500, Glen Lee Edwards wrote:
| Ron writes:
| >
| >> That by itself is good enough for me to try it.  I absolutely dread Red Hat
| >> upgrades.  I don't know why they can't do it so you can just upgrade individual
| >> packages without having to re-install the whole system.  Most of the time when I
| >> upgrade I can guarantee that the box will be down for one to several days.  Ugh!
| >
| >Note, though, that even with Debian, if a package requires, say,
| >perl5.6, and your old stable/Potato box only has perl5, you're
| >going to download a _whole_lot_ of dependant packages.
| 
| I don't have a problem as much with downloading dependencies as I do with
| needing programs that require conflicting libraries.  I'm fortunate in that I
| have an ADSL line that will allow 66+ kB/s downloads, assuming the site I'm
| accessing can handle it.  If the perl dependencies in your example install
| without breaking other dependencies, I'm good to go.

That's the beauty of apt combined with Debian-quality packages.  The
deps Just Work (unless maybe if you run unstable, but that's why it's
called "unstable").

| >A Debian policy-that-I-think-is-a-quirk: there is the the concept 
| >of the meta-package.  mail-transport-agent is an example.  When,
| >for example, you install exim, mail-transport-agent is also 
| >installed.  If you want to install postfix to test it out, apt 
| >will remove exim, since the exim & postfix packages are both 
| >members of the same meta-package.  It won't let me manage 
| >inetd.conf to make sure that 2 different programs are combating
| >for the same port.
| 
| Not sure I'm following what you mean.  Are you trying to get inetd to read
| queries to the port, and based on the query determine which program to open?  I
| don't think you can do that.  Technically it's possible, but based on Internet
| standards my understanding is that specific ports are designed for specific
| programs (protocols).  And trying to get inetd to pick between exim and postfix
| based on the incoming packets I would think would require a complete rewrite of
| inet.

I'll explain with an example :


root@laptop # apt-get --simulate install mail-transport-agent
Reading Package Lists... Done
Building Dependency Tree... Done
Package mail-transport-agent is a virtual package provided by:
  zmailer-ssl 2.99.55-3
  exim-tls 3.35-3
  zmailer 2.99.55-3
  ssmtp 2.50.6
  smail 3.2.0.114-4
  sendmail 8.12.3-4
  postfix-snap 0.0.20020115-5
  postfix 1.1.4-2
  nullmailer 1.00RC5-16
  masqmail 0.1.16-2
  exim 3.35-1
  courier-mta 0.37.3-2
You should explicitly select one to install.
E: Package mail-transport-agent has no installation candidate

root@laptop # dpkg -l exim
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed
|/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad)
||/ Name                               Version                            Description
+++-==================================-==================================-=============================
hi  exim                               3.35-1                             An MTA (Mail Transport Agent)

root@laptop # apt-get --simulate install postfix
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
  postfix-ldap postfix-pcre
The following packages will be REMOVED:
  exim
The following NEW packages will be installed:
  postfix postfix-ldap postfix-pcre
The following held packages will be changed:
  exim
0 packages upgraded, 3 newly installed, 1 to remove and 5  not upgraded.
Remv exim (3.35-1 Debian:testing) [mutt pms mailx ]
Inst postfix-ldap (1.1.4-2 Debian:testing) [mutt pms mailx ]
Inst postfix-pcre (1.1.4-2 Debian:testing) [mutt pms mailx ]
Inst postfix (1.1.4-2 Debian:testing)
Conf postfix-pcre (1.1.4-2 Debian:testing)
Conf postfix (1.1.4-2 Debian:testing)
Conf postfix-ldap (1.1.4-2 Debian:testing)

root@laptop #

I have exim installed.  It "provides" the virtual package
mail-transport-agent.  postfix also provides mail-transport-agent.
Both conflict with mail-transport-agent.  If I try to install one of
them, the other will be removed.

It's supposed to be a feature, and fortunately packages can be removed
without obliterating their config files, and apt stores package files
in /var/cache/apt so it isn't too painful to switch back and forth
(unless your machine thrashes when apt runs).

-D

-- 

One man gives freely, yet gains even more;
another withholds unduly, but comes to poverty.
        Proverbs 11:24
 
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