Author Archives: admin

Arduino development with Eclipse

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The Arduino IDE is great for beginners: It makes it really easy to write simple programs without having to care about compiler options, include paths, language standards or how to actually flash firmware onto the microcontroller. It even comes with a built-in serial monitor which can be a great tool for debugging. Inevitably, as people dive deeper into the world… Read more »

Updating BIOS firmware via iPXE

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These days mainboards usually come with some sort of wizbang tool that allow the user to update the BIOS from a USB drive or straight via network. Except, of course, that one single mainboard that absolutely needs a new BIOS version on a late Friday afternoon. And obviously the manufacturer only provides a flash tool for DOS and the mainboard… Read more »

Migrating a virtual machine from KVM to ESXi

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Migrating a virtual machine from one host to another is usually no big deal if both hosts run the same VMM. But what if one wants to move a VM from a host running a different hypervisor than the target host? In the case of moving a VM from KVM to ESXi that’s just not (easily) possible. However, one can… Read more »

OpenSSH cipher performance

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The achievable speed of copying a file with OpenSSH (e.g. with scp) will depend on quite a few different factors such as CPU speed, CPU architecture, Network throughput, OpenSSH implementation, OS, hard drive speed, etc. But how much of a difference does choosing a different cipher algorithm make? And what’s the fastest OpenSSH cipher algorithm? Turns out, there’s no simple… Read more »

Netbeans’ tomcat log file path

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Spawning a tomcat server instance from within Netbeans is really handy for rapid Java Servlet or JavaServer Pages application development. Since log levels are usually quite verbose during development, logs tend to pile up. So you might want to clean out the log directory from time to time. Or maybe you just want to go through one of those logs… Read more »

Creating a zfs pool on RAM backed block devices

Especially for performance benchmarks it can be quite handy to have a zfs pool that’s not limited by the speed of the underlying hard drives or other block devices (like iSCSI or fibre channel). The Linux kernel has a nice block device driver that let’s you create virtual block devices that are RAM backed. To list the available options, use… Read more »

Change keyboard configuration in console

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To temporarily change a console’s keyboard mapping there’s loadkeys, a little user space program that allows you to alter the kernel’s keyboard mapping. Loading the very handy US International keyboard layout, use To list the currently used keyboard layout or all available keyboard layouts, localectl can be used If localectl is not available, keyboard mapping files are usually found at… Read more »

Convert a JAR file into a Linux executable

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With Java programs it’s quite common to combine several classes into one JAR archive. Java libraries are typically distributed this way as well. On Linux platforms, people are quite used to using command line programs, but sometimes it’s handy to distribute a java program as an executable file that can be run by a simple double-click instead of opening a… Read more »

Command-line deploy vCenter appliance (VCSA) 6.0 on a Linux machine

Up to version 5.5 a vCenter appliance was usually deployed by importing the corresponding ovf template that could be downloaded from the VMware website. That process changed with version 6.0 since there is no longer an ovf template. Instead, VMWare provides and ISO image that contains the necessary data and tools to deploy a vCenter appliance, even directly from the… Read more »

Tunneling browser traffic through an ssh jumpbox

It can be very handy sometimes to tunnel your browser’s traffic through a secure channel, for example when you are on an insecure or unknown network like a hotel, cafe or airport etc. To open up a SOCKS proxy on port 8080, run To configure Firefox to use the proxy go to Edit → Preferences → Advanced → Network →… Read more »