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CentOS 8: first impressions and repo related
Okay. So CentOS 8 is out. Building first few development platforms and few database servers out of it last days, there is a little bit to share.
First of all, the kernel is actually faster. It's newer (4.18+) and contain many later optimization that CentOS 7 has, so it's no wonder. I assume it to be on par with UEK5 (4.14+) or even faster at that. AMD support for my home PC is also good despite it complaining about my Ryzen CPU not being extensively tested, but it behaves better than CentOS 7 under Hyper-V, at least I do see a slight improvement in compilation and response times. This is of course most probably due to GCC being newer as well, but a distinctive part of the RPM package building process is not the compilation itself, that goes faster as well. May be related to rpmbuild optimizations though. But I also see some performance improvements on newer MariaDB servers I built on 8 recently, so it's not only GCC and rpmbuild that matter.
Phoronix posted some preliminary tests of the newer system compared to earlier, and it seems that indeed kernel version makes a big difference there: https://www.phoronix.com/scan.php?page=article&item=centos-8-benchmarks&num=2 . I'm pretty set on using CentOS 8 as a base platform from now on.
I also like the base system memory footprint after cleaning the system up. In CentOS 7, it was hard to untie multiple dependencies when cleaning up the system. It had avahi running, it had tuned almost mandatory and so on, resulting in slightly below 200M footprint in most cases. In CentOS 8, and that surprised me first, actually, I managed to remove tuned (which I don't like and don't use) and polkit, and there was no avahi installed by default. After cleaning this and a bit more of stuff, the clean minimalistic system memory footprint was ONLY 80MB. That came as another good surprise. So with CentOS 8 we can actually build tiny, smaller and tidier systems, without putting in too much effort. And yeah, it even boots faster after all the cleanups.
There are also few spoons of tar though in this big honey barrel. First of all, not all development packages (-devel) are present in CentOS 8 repositories. When I started building hosting system patched httpd 2.4.41 and PHP 7.3 package as the first test, I had around eight missing -devel packages on my hands. It boiled down to downloading source RPMs (luckily they were there), building them (fixing .specs for few along the way) and then throwing everything besides -devel away. Self-built -devels install well, and are going okay with the native binary packages. In the end, I was able to build both httpd and php specific versions without having many issues.
What comforts me, is that there are backwards compatibility iptables and network scripts packages included. I was terribly afraid they ditched it in favor of nft and NetworkManager, but I was wrong. Classic network scripts are written to complain about deprecation, but well, who cares (did not even remove the message). They still do their job well without much extra bloatware, and that's all I need around. As it occured, actually some CentOS 7 packages can also be installed into 8 without scratch because major compat dependencies are present, but anyways I heavily recommend against it.
The thing to be wary of is new DNF package manager package removal behavior. By default, when you remove some package having dependencies, it removes all orphan dependencies you have not installed by hand. So imagine you have installed rpm-application-1 that requires rpm-library-2 (which was installed as dependency), and then if you remove rpm-application-1, rpm-library-2 will also be removed if not used by any of the remaining packages. While this looks handy on the first glance, it resulted in my system losing few packages I used like tar when I removed some bloat. So the thing to keep in mind: if you want some package to remain after you remove all other packages dependent on it, yum install it manually and first.
Another thing that grazed me is incompleteness of not only base but third party repositories as well: MariaDB (which has packages actually present, but absent in metadata), EPEL, etc. Seems like everyone in the world was terribly hurried with this one release, and number of launch mistakes here and there is pretty high due to that. Because of that, I'll i.e. build my own packages of some new and older EPEL stuff and won't even bother with adding EPEL to the repo list as I did with 7. During the launchtime (and later on as well, but less pressing), the less third party repositories are there, the less problems are to be encountered.
So, what all this means. This means CentOS 8 is not without issues, but is totally usable, so I'll be posting hosting system packages in my repository for CentOS 8 soon enough. CentOS 7 packages will continue to be there for a good while though.