Disaster proof backup at home

March 23, 2017 Backup, Disaster Recovery, Linux No comments , , , , , , , , , , , , ,

Backup design

This article describes how to build a affordable, disaster proof, multi site backup with commodity hardware.

You never know, when disaster strikes and wipes out all your data. With the upcoming move from Munich to Karlsruhe, I’m really concerned about losing data during the move. To give some background: I use a Synology Diskstation DS1815+ as a central data store. It has currently around 16TB of capacity of which about 9TB are in use.


Power consumption of the J4205-ITX under Linux

March 10, 2017 Hardware, Linux 2 comments , , , , , , , ,

After assembling the J4205-ITX and installing Linux, I was looking forward to testing the power consumption. Goal of the project was to build a low energy consumption VM-hosting server.


Installing Linux on the J4205-ITX

March 8, 2017 Hardware, Linux, Technology 6 comments , , , , , , , , , ,

This article describes how to install Debian Linux on the J4205-ITX based server described in Building a low energy consumption server  for hosting VMs.

The firmware files for the network interface are not shipped with the debian installation


ASRock J4205-ITX – A low energy consumption server for VM hosting

March 7, 2017 Hardware, Linux, Technology 5 comments , , , , , ,

Goal of this project is to build a completely passively cooled, low energy consumption server, which can host VMs. It has 16 Gigabytes of RAM and runs KVM.


Network design for Karlsruhe

March 6, 2017 Hardware, networks, Technology, Ubiquiti No comments , , , , ,

XCore Networks Karlsruhe - VLAN design

Designing a network with Ubiquiti equipment.

As some of you might already know, we are moving back to Karlsruhe. This will be a good opportunity to redesign our internal network. The goal of the redesign is to decrease complexity, increase throughput and to reduce the power requirement for the networking equipment. It would also be a nice side effect, if none of the new equipment had active cooling / fans.

The plan is, to replace all of the “Enterprise Equipment” (Juniper, Cisco, HP) with Ubiquiti equipment.


F5 BigIP iControl: Working with pools

August 14, 2014 F5, networks, Uncategorized No comments , , , , ,

The iControl pool interface is a bit tricky at first. The reason is, that most of the methods support a list of nodes as well as a list of pools as arguments. I think the reason is to reduce roundtrip costs during calls as well as making the interface more atomic. The problem is, that you end up with some ridiculously nested parameters when using Perl.


F5 BigIP iControl: Understanding pool member states.

August 14, 2014 F5, networks 2 comments , , , ,

When you look at a pool member in the web ui, you might have noticed, that a node can be set to two different states:

– Enable (All traffic allowed)
– Disabled (Only persistent or active connections allowed)
– Forced Offline (Only active connectoins allowed)


Unfortunately if you look at the node from an iControl perspective, it’s not quite that obvious. The thing is, that there are actually two different types of state for a pool member:
– Monitor state
– Session state


Controlling F5 BigIP loadbalancer from Perl

August 14, 2014 F5, Technology No comments , , ,

One of my customers recently migrated to F5 LoadBalancers. Those devices are pretty nifty and provide a lot of nice features. One of the nicer ones is the iControl. iControl provides access to the configuration API via SOAP. This means, you can use it from your favorite programming language.

Although the documentation is sufficient, I had quite some experiments to do until I got it running with Perl correctly. Therefore I will document my findings here.


Debian unstable: dist-upgrade just broke my VMWare video driver

July 6, 2014 Linux, Uncategorized No comments , , , , , , ,

After applying an dist-upgrade to my Debian unstable, the vmware-driver for the display suddenly stopped working. It just showed a black screen and then froze. After logging in via SSH and having a look at the X11-Logfile, it turned out, that the driver actually died in an segmentation fault (SIGSEGV).

Thanks to the awesome VMWare AutoProtect Snapshot feature, I could quickly recover to a working system. But the problem still bugged me – so I started investigating.

After ruling out the obvious culprits (The vmware driver itself, libc6, vmware-tools etc.), it turned out, that the real culprit actually was “libxatracker2”. Luckily I still had an older version lying around in /var/cache/apt/archives. After rolling back ( dpkg -i /var/cache/apt/archives/libxatracker2_10.1.2-1_amd64.deb ) everything worked like a charm. Until the problem is permanently resolved, I applied the following hotfix:


Package: libxatracker2
Pin: version: 10.1.2-1
Pin-Priority: 1001

Essential sysadmin skills in 2014

July 3, 2014 DevOps, Linux, Work No comments , , , , , , ,

My list about the stuff every sysadmin needs to know nowadays.