[CentOS] What are the differences between systemd and non-systemd Linux distros?

Fri Oct 19 13:12:08 UTC 2018
Warren Young <warren at etr-usa.com>

On Oct 19, 2018, at 5:07 AM, Simon Matter <simon.matter at invoca.ch> wrote:
> - the upgrade path from EL6 to EL7 is completely broken.

Under what conditions would you actually use it?

As we can see from the repeated attempts to get a reliable in-place upgrade process working, the community doesn’t seem to have much interest in the idea:


I believe this is because in-place upgrade is antithetical to the idea of a “stable” Linux distro in the first place.  Once something’s configured and running, you just want it to keep doing so.

In my world, OS upgrades are generally paired with new hardware or VMs.

I did just this on an Ubuntu VM recently, which does have an in-place upgrade system.  I’d been ignoring its motd offers of upgrade for years, on purpose, and only upgraded it from 14.04 LTS to 18.04 LTS when I needed to rebuild the VM anyway.

That’s why I was on an LTS release in the first place: to give me the years of stability that let me batch the changes up into a single big-bang upgrade.  CentOS is even better in this regard, with version lifetimes up around 10 years, rather than 5 for Ubuntu LTS.  One of the reasons I chose to upgrade it recently was because Ubuntu 14.04 is about to fall out of support, so it was time to move.

I believe a lot of the antipathy toward systemd is that people want “LTS” to be forever.  That’s not going to happen until the rest of the world stops changing.  That would be a very sad thing: it’s basically a wish for stagnation.

If upgrading via separate hardware or a new VM is difficult, it calls into question the usefulness of your backup and restore strategy.

Another advantage of this style of upgrade is that you have the prior box online and ready to fall back to if the manual upgrade fails.  If an in-place upgrade fails, you’ve just lost the primary.