[CentOS] C7 systemd and network configuration

Tue Apr 21 15:31:59 UTC 2015
Jonathan Billings <billings at negate.org>

On Tue, Apr 21, 2015 at 09:46:51AM -0500, Johnny Hughes wrote:
> I have decided it is likely better to bite the bullet and learn how to
> use and configure Network Manager if you are going to do anything other
> than very simple things with your network .. at least on CentOS-7 or
> higher (ie, Fedora > 18, etc.).

A lot of the problems I had with NetworkManager was that even though
NM started fairly early in C6, often the network wouldn't be up by the
time later-starting services started (since NM didn't block on
network), and anything that needs to do a DNS resolution or some sort
of initial sync on start would fail.  Even worse, if you had both the
'network' and 'NetworkManager' services started, the network would be
brought up with the 'network' service, then NM would start, and
sometime mid-boot the network would drop then be re-started as NM took
over.  So it'd be a form of russian roulette as to which service would
not have a network during boot.

In C7, services have dependencies on the network-online.target, which
fixes a lot of the issues I mentioned above.  One of the nicer things
of having actual service dependencies.

Jonathan Billings <billings at negate.org>