Moving towards NetworkManager

[Josef Wolf]

Hello folks,

Currently, I am configuring network setup myself via automated scripting.
This setup (for laptops) is based on wpa_supplicant and ifplugd to switch
and reconfigure networks.

I have checked network-manager about six years ago, but for some reasons it
did not fit. I don't remember the details, though..

Motivated by this thread
(https://lists.ubuntu.com/archives/ubuntu-users/2016-July/286270.html),
I'd like to take another try on that. After all, people claim NM has matured
since then.

So I deactivated network setup in my configuration scripts and did a fresh
install on a laptop, just to see what NM would do by default.

I have (not yet) entered any WiFi-Keys for now.

Here's what I see:

0. First of all, NM is not available on the server install CD. So I need a
   working network to install NM. Somewhat ugly this bootstrap situation. I
   decide to ignore this for now.

1. When the system is booted without ethernet-cable connected, it hangs for
   about 6 minutes. After this time this routing information is added:

  Dest            Router          Genmask         Flags Metric Ref    Use Iface
  0.0.0.0         0.0.0.0         0.0.0.0         U     1002   0        0 enp0s25
  169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 enp0s25

  If I plug the ethernet cable later, the routing table won't be updated. I
  need to manually do an ifdown/ifup cycle to get a working routing table:

  Dest            Router          Genmask         Flags Metric Ref    Use Iface
  0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 enp0s25
  169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 enp0s25
  192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 enp0s25

  with my previous setup, I used ifplugd to change network configurations when
  a cable is plugged. Won't NM take care of that?

2. I invoke the "manage connections" menu from the system tray and create an
   ethernet connection. I check the "all users" and "connect automatically"
   checkboxes. The config is saved in /etc/NetworkManager/system-connections.
   But unplug/plug still won't have any effect on the routing table. Ifplugd
   did a much better job regarding to "managing the network".

3. Then I go to the menu in the system tray, choose a wifi-AP and enter the
   wifi-passphrase. But the wifi won't come up.

4. I choose "Manage connections" and choose the same AP as before. I change it
   to be used by all users. But the "save" button stayes greyed out, so I cant
   save it.

5. I choose the same AP via system tray again. I am asked for the passprase
   again. Was it not saved the first time? This time a message is displayed
   that the wifi is now connected.

6. I check the routing table: both interfaces (ether and wifi) have routes. I
   unplug ether. The routing table won't be adjusted and consequently, network
   stops working because ether routes take precedence.

7. I need to manually "ifdown". After that, networks starts working.

8. I plug in ether again. I'd expect wifi to go down in favour of ether, just
   as my ifplugd setup did it. But nothing happens.

9. I reboot the system, ether disconnected. My ifplugd-based setup would fall
   back to wifi immedeately. NM waits 6 minutes again.

10. I check the routing table, and indeed, both interfaces are active. But
    this time wifi takes precedence. I switch off the wifi-router, and voilla:
    networking stops working. Unplugging/plugging ether don't help.

I'm wondering why they call it networkMANAGER?

What does this piece of software ACTUALLY manage?

What am I missing here?

-- 
Josef Wolf
jw at raven.inka.de