Re: systemd network interface configuration (was "Re: systemd woes continue")

[Bob Tracy]

On Thu, Sep 19, 2019 at 09:10:20AM +0200, John Paul Adrian Glaubitz wrote:
> (...)
> So, can you please type "ip a" and check what device name is actually assigned
> to your wired card and if it differs from "eth0", adjust your /etc/network/
> interfaces file?
> 
> If your wired card is actually named "eth0", then the problem is somewhere
> else and we need to proceed in your next mail.

The wired card really *is* "eth0".  "ip a" shows five interfaces in the
current active (correct) environment:

1: lo
2: eth0 (my primary network interface, connected to a pre-CIDR routable
class C network)
3: enx00e04c6881f7 (USB NIC connected to an internal non-routable class
   C network)
4: sit0@NONE (tunnel for IPv6-in-IPv4 traffic)
7: he-ipv6@NONE (a point-to-point IPv4 connection to the IPv6 tunnel broker)

The wireless interface in the "interfaces" file corresponds to a USB
adapter I haven't used with the Alpha in a long time.  I left the
configuration info there as a reminder of how to do that if/when it
becomes necessary :-).

At the risk of providing too much information, the Alpha is serving as a
local IPv6 gateway router.  "/etc/sysctl.conf" has
"net.ipv6.conf.all.forwarding=1" which is appropriate (required) for a
router, because otherwise, "radvd" will "unexpectedly" configure an
additional global IPv6 address for "eth0" which you definitely do not
want.  The only global scope IPv6 addresses are statically assigned to
the "eth0" and "he-ipv6" interfaces.

There remains a bit of strangeness, even if/when the interfaces are
brought up correctly, because of the "gateway" configuration line
associated with the USB interface.  I need to comment that out: multiple
default routes at identical priorities is a legitimate configuration
error in my setup.  At one time, there was a legitimate reason for that
gateway line to be there: no need to go into that level of detail at
present :-).

--Bob

Re: systemd network interface configuration (was "Re: systemd woes continue")

[John Paul Adrian Glaubitz]

Hi Bob!

On 9/19/19 7:09 AM, Bob Tracy wrote:

On Wed, Sep 18, 2019 at 11:46:06AM +0200, John Paul Adrian Glaubitz wrote:

Your permanent bashing of systemd makes answering your mails stressful
for me.


Adrian -- please accept my apology for my rantings...  They contribute
nothing to the conversation, and as you note, irritate the very people
in the best position to render needed assistance.


It's okay. Let's try to tackle your remaining problems.


Going back to a previous message you sent, you suggested looking at a
few systemd network-related services:

(1) systemd-networkd: this is currently showing "disabled" on my system
 (vendor preset: enabled).

(2) resolver-related systemd services such as "resolvconf" and 
"systemd-resolved":
 "resolvconf" is "enabled", but "systemd-resolved" is "disabled"
 (vendor preset: enabled).

None of the services mentioned above have any configuration files other
than the defaults.


Both systemd services here are "systemd-networkd" and "systemd-resolved" and
both are disabled by default. "resolvconf" is not related to systemd.


So, I guess the main question on the table is, what's the best path
forward to ensure network interfaces are brought up and configured
automatically at boot time?  Related to that question: is the use of
"/etc/network/interfaces" deprecated?  That's where my network
configuration details currently exist, and that used to be sufficient,
even after the migration from the old-style init program/scripts to
"systemd".  A sanitized copy of my current "interfaces" file is
attached.

Using /etc/network/interfaces should still work, so the easiest thing
to do would be to check whether your interface names have been renamed.

Looking at your /etc/network/interfaces, I can see that you are using
the modern driver-oriented device names while for your cable connection
you are stuck with eth0.

So, my assumption is that udev is indeed renaming your network interfaces
and while you (or some script) has set the new interface names for your
wireless card in /etc/network/interfaces, you are still using "eth0" for
your wired network card.

So, can you please type "ip a" and check what device name is actually assigned
to your wired card and if it differs from "eth0", adjust your /etc/network/
interfaces file?

If your wired card is actually named "eth0", then the problem is somewhere
else and we need to proceed in your next mail.

Adrian

--
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaub...@debian.org
`. `'   Freie Universitaet Berlin - glaub...@physik.fu-berlin.de
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