Yubikey two factor authentication for ssh

March 8, 2019    Tags: yubikey  2fa  ssh  yubico


After my successfull sudo test I was interested in 2fa for ssh. As a systemadministrator you are always scared about secure login just for you/your team.

Also ssh 2fa via yubikey is pretty straight forward. It needs some more work than just the sudo case but here we go.

Yubikey for sudo 2 Factor Auth

Dec. 7, 2018    Tags: yubikey  2fa


Some days ago I thought about testing two factor authentication (2FA) with Yubikey. Yubikey is a hardware security key which can do a lot.

How to test 2FA on a local machine if you don’t want to log you out or destroy anything important? I decided to implement 2FA for sudo command with yubikeys U2F feature. Be aware: This does not work for ssh.

handle kvm static ip adresses

Nov. 27, 2018    Tags: virsh  kvm

I did a lot of work with libvirt and kvm and for some hosts I wanted to have a fixed IP address but not configured on the host itself. I wanted to get it from dhcp.

Minikube increase disk size

Sept. 10, 2018    Tags: minikube  docker  testing  kubernetes


I did some more research and development with kubernetes and minikube. During some tests where the diskspace of one node got bigger than 16GB and I saw a message about DiskPressure in the logs, I figured out that minikube has a default disksize of something around 16GB.

Check if a file was changed in a bash script

Aug. 3, 2018    Tags: letsencrypt  unix  debian  bash

I’m using letsencrypt for most of my servers. One of these servers is behind a firewall without any direct internet connection. Therefore I’m not able to use letsencrypt or dehydrated directly on that server. I’m copying the certificate to a specific location as a normal ssh user and on that host itself I have to check if the certificate was changed to reload the webserver.

Puppet could not retrieve catalog...

July 28, 2018    Tags: puppet

Some days ago I got an error on one of my puppet agents which I can’t really explain. Everytime I executed my puppet agent (puppet agent -t -d) I got the following error:

Could not retrieve catalog from remote server: \ Could not intern from text/pson: "\xC2" on US-ASCII

pm-suspend on Ubuntu

Nov. 2, 2017    Tags: pm-utils  pm-suspend

After upgrade to Ubuntu 16.04 I recognized that pm-utils are not used anymore to suspend/resume my notebook. The change was already done with Ubuntu 15.04, but I haven’t recognized it before, because everything was working like expected. I recognized it these days after I changed my windowmanager to i3wm.

Since Ubuntu 15.04 they don’t use the pm-utils like pm-suspend any more. They use now systemctl commands to suspend if the lid is closed. Therefore my screenlock was not working any more and I had to adapt some things to get the i3 screenlocker i3lock ...

How to use grafana scripted dashboards

Oct. 17, 2017    Tags: prometheus  dashboard  grafana

I’m using prometheus to collect metrics of java applications or unix systems. On top I configured grafana just to have a nice an shiny view and to get the possibility to add dashboards and to save my graphs somehow. Grafana is pretty nice to add graphs in a fast way to new dashboards, but what happens if you have, like I have, a lot of metrics which change or new hosts are getting added. That’ something you don’t want to do by hand. Therefore grafana implemented the “scripted dashboards”. I figured out, that the documentation of these dashboards ...