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From: Reco <recoverym4n@enotuniq.net>
Newsgroups: linux.debian.user
Subject: Re: Still unable to restart networking on Debian 9 text mode only
Date: Fri, 23 Nov 2018 13:50:01 +0100
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	Hi.

On Fri, Nov 23, 2018 at 10:31:28AM -0200, Luciano Andress Martini wrote:
> Good morning,
> 
> IMPORTANT: Network Manager was not being installed automatically by
> the Debian DVD when I do not mark the graphical interface.

An excellent news. Let's hope that Debian continues to behave this way.


> Then I edited /etc/network/interfaces and restart the system, to see
> if the ip was changed. And yes, it worked. So this file is still being
> used in some way - humm that seems to be the correct place to
> configure my interface isn't?

So, in plain English, you have ifupdown installed.


> Well, I edited it again, now to try change the ip but without
> restarting the system - like in all servers real situation, you don't
> want to go after the server. First of all I tried all this solutions:
> 
> #systemctl daemon-reload
> (nothing happens ip didnt change)

And it should not. ifupdown provides networking service, and
"daemon-reload" forces systemd to re-read own config only, not to
restart services.


> #systemctl networking restart
> (the ip did not change and the connection breaks you need to go
> phisicial and ip address shows the same ip configured)

"networking restart" invokes "ifdown" first, and "ifup" next.
And systemd restarts most of the network services by dependency.
The problem is - once they invoke ifdown, there's no network connection
to invoke "ifup", hence you have no network-listening services.

Do it from BMC/ILOM/HMC (it's not a server if it does not have one), or
install screen/tmux and do it from there.


> #nmcli connection reload
> # nmtui

Please leave these Finely Designed Executables™ to a desktop
installation.


> 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

ifdown/ifup combo should be sufficient. Just don't do it via plain ssh
connection.


> But if for example i do it partially, it does not work... for example:
> 
> ip address delete theoldip/mask dev enp0s3
> ifup enp0s3
> The interface is already... blabla

ifup/ifdown have their own special way to track which interface was
touched by them. ifup will rightfully refuse to bring network interface
UP if it considers that it's UP already.

> 
> ifdown enp0s3
> ifup enp0s3
> (a new ip is added to the interface, but now two ips are configured
> and the network is broken again)

You mean, two new IPv6 ips? Can you provide a 'correct' and a 'broken'
example via 'ip a l' please?
And, while we're at it, the contents of /etc/network/interfaces?

> Is that a bug?

Short of the last part everything else can be classified as an
operator's error, or a lack of knowledge.

Reco