Linux: concerns over systemd [OT]

Thu Oct 23 06:55:40 UTC 2014

On Thu, Oct 23, 2014 at 12:28 AM, George Herbert
<george.herbert at gmail.com> wrote:
>
> Ok.  As a highly on- list-topic example of why distrust is called for...
>
> Without referring to the systemd source code*, does anyone know what systemd uses to select between networking subsystems (i.e. NetworkManager, the new standard as of RHEL 7, vs /etc/ sysconfig/network-scripts/, etc.).  NetworkManager is default but disableable and it magically falls back to network-scripts dir, but the fallback is nearly undocumented and the selection behavior appears completely undocumented.

systemctl status NetworkManager.service
systemctl status network.service

I don't think that there's anything magic about it, you have one or
the other enabled.  Adding NM_CONTROLLED=yes/no to
/etc/sysconfig/network-scripts/ifcfg-* gives you per-interface control
over whether NetworkManager or the network scripts are used for
managing the interface.  If neither is enabled you probably end up
with no networking.

> If by some chance you do know this, where did you come by that knowledge?  Hopefully with URLs.

I have access to systems that run systemd and I tried a couple of
things...  Also, I've been managing Red Hat systems for a long time
and have known about this for a while.  But a little bit of googling
and I found this:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Networking_Guide/sec-NetworkManager_and_the_Network_Scripts.html

Unless you're running systemd-networkd, this is really distro-specific
stuff as I expect that most distros will want to preserve some
backward compatibility with "legacy" network configuration.

-- 
Jeff Ollie