Cfrtjryk

First of all important:

• Debian does not install NetworkManager by default if you run install it on text mode. (I received some answers considering that I did not get how to configure Network Manager)

Well, I am trying to figure out why I just can't restart the networking configuration without a system restart, or doing some commands by hand.

service networking restart 

Does not have any effect as everybody knows.

ifdown ensp0

Says that the interface is not running....

What I'm doing is using the ip command, to remove all the ips one by one, then bringing them all up with ifup. However that is very strange.

So in a way what is the correct form to just restart all the network connections as we do in the ancient versions?

Should I use network-manager in text mode with nmtui? If so, Why is Debian still installing /etc/network/interfaces by default and not nmtui? And why is network/interfaces working when the system is restarted?

If I add:

auto enps0 

Then networking starts to work better. So I start asking, why this is not the default behavior after the installation? How are the interface is brought up by default, if it is not configured to auto start?

Is this more of systemd issue? Or, it is related to the net-tools being deprecated?

And much much more... But the only thing that I really want to know is, how can i just do a simple restart of the network interfaces, after the installation?

NetworkManager's configuration storage is more versatile than you think.

NetworkManager has multiple different plug-ins for configuration storage. RedHat and related distributions use nm-settings-ifcfg-rh which uses (and extends) classic RedHat-style /etc/sysconfig/network-scripts/ifcfg-* and .../route-* files.

Debian and related distributions, on the other hand, use nm-settings-plugin-ifupdown instead: that reads Debian's traditional /etc/network/interfaces file. Unlike RedHat's solution, this is a purely read-only plug-in.

SuSE also has a NetworkManager plugin that reads their traditional configuration style. Like Debian's, it is a read-only plug-in.

There can be more than one configuration storage plug-in in use simultaneously: all the above-mentioned major distributions also use the nm-settings-keyfile plug-in, which reads & writes configuration files in /etc/NetworkManager/system-connections/. This format can cover more cases than the legacy configuration formats, so it is used as an alternate storage format... although it might eventually become the primary format instead.

If you are using NetworkManager and modify the network configuration manually (i.e. not through nmtui, nmcli or any other Network Manager user interface tool), then you should tell it to reread the configuration when you're done:

nmcli connection reload

which can be shortened all the way to

nmcli c r

Once you do that, NetworkManager will automatically restart the network interfaces as necessary - and only the interfaces that actually need restarting. This works regardless of where your network configuration actually lives.

In modern Debian, there are several ways to configure network interfaces:

• traditional ifupdown, which requires service networking restart to reload configuration


• 
  NetworkManager, which uses nmcli c r to reload configuration


• 
  systemd-networkd, which apparently uses systemctl daemon-reload to reload configuration (I've never tried that yet)

In general, you should decide which configuration method to use: usually for the whole system, but you can use multiple methods in a single system if you absolutely have to. Just make sure you use only one method to manage each interface: if two methods each have a different configuration for the same interface, you're going to see odd behaviors.

I tried a fresh Debian install without graphical interface but using the graphical installator i am running Debian 9.6.

Then i edited /etc/network/interfaces and restart the system, to see if the ip was changed. And yes it worked. So it is being used in some way.

Well, i edited it again to try change the ip without restarting the system.
First of all i tried the solutions from the other answer:

#nmcli connection reload

nmcli connection reload The program 'nmcli' is currently not installed. 

You can install it by typing: apt install network-manager 

nmcli: command not found. 

(my comment: well it seems NetworkManager was not installed is that right?) 



#systemctl daemon-reload

(nothing happens ip didnt change) 



#systemctl networking restart 

(the ip did not change but the connection is now broken, until restart for some unknown reason) 

The solution that i found is this (but i think that is not a real solution):

ip address delete theoldip/mask dev enp0s3 

ifdown enp0s3 

ifup enp0s3 

Or just restart the system after editing /etc/network/interfaces