[lug] Thoughts on upgrading to CentOS 7

[Rob Nagler]

On Wed, Mar 28, 2018 at 10:56 AM, Steve Litt wrote:

> Yeah, that's what I was saying. Once a distro has systemd, swapping in
> runit or s6 becomes extremely difficult. I'm not sure what other
> context one could view it from.
>

Firstly, I have to say I appreciate people like you. We wouldn't have such
stable distros without you! It's very important for people to dig into the
distros to try to keep them honest and robust.

Secondly, my focus is different. My problems have nothing to do with the
distro per se other than it is much harder to upgrade from CentOS 6 to 7
than I (naively) thought it should be. I don't think systemd made it that
much harder other than it being buggier than I would have liked.

Back to your statement, which is sort of a question...

There are distro providers and distro users. I'm a distro user. A distro
provider can change out packages more easily than distro users, because
they are experts in their distro and the general concept of building
distros. As a distro user, I am buying into a lot of policy decisions such
as "we like systemd and gnome." A distro user is going to find it hard to
switch out many policy decisions. My job as a distro user is picking the
right distro. You asked me that earlier in this thread, and you are correct
that maybe I should have considered a different distro since the change
from CentOS 6 to 7 has caused me much more work than I (naively and
incorrectly) anticipated. My bad for not being a more discriminating distro
user/chooser, but I don't have the urge to pop and swap runit for systemd.
Or that somebody decided that users should start at 1000 and users below
1000 now don't get home directories (used to be 500). That's a policy
decision, which has ramifications for useradd. I'm not going to switch out
useradd or even change that magic number. Rather, I will just bump all my
UIDs, because they are located in one file, which generates the useradd
commands. However, the fact is that I had to deal with this non-obvious
change from CentOS 6 to 7.

Imagine that installing Emacs not only disables Vim, but makes so many
> changes to the surrounding software that Vim installation becomes a
> long series of workarounds instead of apt-get install vim.


Well, that's the first sensible thing anybody has said in this thread:
emacs should disable vim. Love it! ;-)

I don't think this is a fair comparison. It would be like saying a distro
should let you plop in a different kernel. Red Hat init scripts are not
compatible with Ubuntu scripts. I don't like that, but that is how it
always was, just like Sys V init scripts were not compatible with BSD
scripts. I was at Sun when we made that change, and it wasn't a lot of fun.
(And, if I remember, there was a lot of fire breathing about that, too.)


> If the criteria is "possible", the entire discussion is moot. Given
> enough resources, I could transform CPM into Linux. The point is it
> would take a very knowledgeable person a day to switch Red Hat to
> runit. It would take a very motivated average Linux power user a month.
> These timings have a chilling effect on switching. I call that a poison
> pill.
>

At the user level, you can transform unit files to init scripts and vice
versa. Have the existence proof of this. :) That actually is very easy. For
me, the hard part is debugging the weirdnesses of how containers work,
which today (for example) was not a very good day. :(  I'm about to create
an existence proof for uncontainerizing a number of applications, which
were already multi-tenant (so why did I think containers were a good idea?
:).

Rob
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