[CentOS] CentOS and typical usage

Mon Dec 14 19:12:18 UTC 2015
Jonathan Billings <billings at negate.org>

On Sun, Dec 13, 2015 at 04:39:05PM +0000, Timothy Murphy wrote:
> Alice Wonder wrote:
> > Just that it is not
> > difficult to use, there are some advantages - 
> Why don't you say what the advantages are,
> instead of launching into a philosophical discussion of "market share".

So, while the parallel startup can sometimes produce a faster startup,
I believe it is more a side effect from the proper management of
service dependencies.  In SysV init, you either had hard-coded
sequential startup of some parts of the OS (in the shell script that
started init and mounted all the filesystems, ran fsck, whatever) and
then the increasibly difficult to manage SysV init scripts, which were
ordered by the chkconfig numbers.  There's no explicit dependencies,
you had to basically modify those numbers if you knew they needed to
start before some other number, and if the packaged init script had a
number that just didn't work out, then you're stuck maintaining that
script for the rest of time.

Upstart tried to fix this, and it probably would have been what we're
all using instead of systemd if their development process wasn't
broken.  But even when we had Upstart in CentOS6, no one wanted to use
it, they all used SysV init scripts.

As a sysadmin, I like systemd because I can finally manage the order
in which services start up and keep my sanity.  Don't like how the
packaged unit does something?  Its easy to override a setting or write
your own, and you don't have to worry about the package overwriting
it because its a separate file in /etc.

As a packager, I like systemd because I can write one service unit
file, and know that I don't have to worry about the ordering of
services, and I even get some cross-distribution portability.

Jonathan Billings <billings at negate.org>