Month: September 2018

Networking with Hetzner

Setting the scene

Recently I found out the hard way that Hetzner frowns upon MAC addresses on their switch ports they don’t know, so they blocked my server.

What happened: The wan interface was a member of the bridge connecting my virtual machines, because from what I knew back then that was the only way to provide the VMs with IPv6 addresses from the Hetzner subnet. So their MAC addresses (52:54:…) went out to the switch. This was so bad that they didn’t even allow me to unlock it temporarily to fix the problem!

What I did: Reboot the server via the robot to shut down. They aren’t started automatically on boot. Then notify Hetzner via the robot that I fixed the problem by reconfiguring the network configuration. They replied very quickly by checking for foreign MAC addresses and, since they found none, unlocked my server. Now I had a chance to reconfigure the network without using their hardware KVM.

The fix

First thing to do, was remove the wan interface from the bridge. That was a remnant from a completely bridged setup from long ago, anyway. Since all IP4 traffic was routed, that wasn’t a problem. IPv6 was a problem, though. The router announcements from radvd worked, but neighbor discovery didn’t, so the VMs didn’t have IPv6 connectivity.

I finally found this article: It boils down to:

  • Give the wan interface a single IPv6 address from your assigned network (netmask /128) to make it a part of it.
  • Assign the bridge the same address, only with a /64 netmask!

The article does it for Debian. Translated to systemd-networkd I ended up with this:

The wan interface

/etc/systemd/network/wan.network

[Match] 
Name=wan <- The interface name is set by an udev rule

[Network] 
Address=2001:db8::2/128 <- /128 is the clue!!!
Gateway=<replace.with.ipv4.gateway>
Gateway=fe80::1 <- This is literal!!!

[Address] 
Address=<your.ipv4.address>
Peer=<the.peer>/32

Create the bridge

[NetDev] 
Name=br0 
Kind=bridge

Do not attach the wan interface to the bridge!

Configure the bridge

[Match] 
Name=br0 

[Network] 
Address=192.168.0.1/24 <- Your private IPv4 VM network
Address=2001:db8::2/64 <- YES, this is the same address as wan!

Don’t be alarmed if br0 is not configured and down on reboot. Once you start a VM using the bridge it will be taken up and have all the right addresses. If you add the IPv6 address manually with ip, you will loose IPv6 connectivity, since the kernel creates a useless default route! You have been warned!

Works like a charm (for now)!

Bold font in KDE konsole

To get a bold font in Konsole, do this:

  • First, create a new Profil
  • Edit the profile to use DejaVu Sans Mono, Size and Style doesn’t matter
  • Save it and close Konsole
  • Edit $HOME/.local/share/konsole/<Profile Name>
  • Add or replace the Font Entry under Appearance with
Font=DejaVu Sans Mono,9,-1,0,75,0,0,0,0,0,Bold
  • Now edit $HOME/.config/konsolerc and add
[Desktop Entry] 
DefaultProfile=<Profile Name>
  • Replace [Favorite Profiles] with
[Favorite Profiles] 
Favorites=

Kill all instances of Konsole, start it and never touch that stuff again!

Archlinux and an AMD-GPU

I finally decided to get rid of my ancient nvidia graphic board and bought a Sapphire Radeon R5 230 with 2GB RAM for 46,40 €uros. The vendor chose GLS as delivery service, so no tracking number. Of course it didn’t arrive at the announced day. I had to ask the vendor and eventually picked it up in a not so close boutique.

Well, once I had it, assembly wasn’t much of a problem. Configuring X was. Took me five hours to get it right!

First, I had to figure out which driver to use, which isn’t as easy as it seems. Turns out to be radeon, not amdgpu. Without any configuration the radeon kernel module is loaded, which is right, by the way, but X can’t figure out what driver to use. By default it uses amdgpu if installed. Well, wrong choice.

Create a configuration with

# X -configure

and change the Driver from amdgpu to radeon. Then remove the vnc module in Section “Module” and the Screens in Section “ServerLayout”. X identifies 2 Devices, one for VGA output, and one for DVI, or so I thought. Actually, the card has another output: HDMI for TV-out, which happens to be the default. Very clever! Disable it by adding this to the kernel command line:

video=HDMI-A-1:d

Now set the option ZaphodHeads to “VGA-0,DVI-0” in both device Sections. That should get you up and running. SDDM still doesn’t work, but startx will. SDDM requires some xrandr magic in Xsetup, which I haven’t figured out yet.

Anyway, it was worth it! No more annoying delays when playing videos while writing text in LibreOffice! In total the system feels much faster now.

You can marvel at the whole config here.