Posts
- Dec 21, 2016
New: Sketch Recognition
Two years ago I worked on a subsequence matching algorithm, to solve a difficult data monitoring problem with tight algorithmic time and space complexity requirements. I went back to restart documenting this case. Now, instead of publishing my old results, I decided to make up a new challenge, to test and improve my findings. I created this task around a little web project, in order to show and use it as an interactive example: Sketch Recognition.
Read more - Dec 20, 2016
HowTo: Enlarge a Virtual Drive on VMware vSphere
In the past we had to upgrade our VMware vSphere virtualization server and its virtualization hosts machine VMware ESXi. An old virtual debian machine has had multiple
Read moredist-upgradeiterations in its life and it even survived the VMware upgrades from V4 to V5.5. Back then it was running an important OwnCloud instance and the virtual disk on this machine was eventually running out of free space. That’s when I was confronted with the virtual disk space enlargement. - Dec 19, 2016
Snippet: password generator on Windows
Once given the task to create about a hundred of (unsimilar) Active Directory users on a Windows domain controller, I needed a batch script to create random passwords to my clipboard. The constrains were clear: alphanumeric
Read more[a-zA-Z0-9]with minimum and maximum character count. A double-click is all that’s needed for execution. - Dec 18, 2016
Docker: Domain Controller with Samba
I worked some time in a company environment traditionally build around Microsoft’s Active Directory and I liked the user and group management, even the administration of their privilege setttings. We ran several virtual Debian machines to host webservices, which authenticated their users via LDAP and Kerberos. Luckily as developers, we do not need to purchase any Microsoft product for building or testing. All you need is a Domain Controller docker image.
Read more - Dec 17, 2016
Revisited: IsDriven / IstMobil - a carsharing platform
I would like to take the time and present a website project I’ve worked on together with a couple of good friends up until early 2013. Here, the promising idea was to bundle the most interesting topics of carsharing to one highly interactive website: IsDriven.com
Read more - Dec 16, 2016
Meta: Run local Jekyll blog with docker
- Dec 15, 2016
Meta: Jekyll with tags and categories
Once a decent number of blog posts and pages on a single domain is reached, it becomes necessary to sort and categorize single posts. That way sequential articles can be written or information on a common topic be grouped. Since GitHub Pages do not support custom Jekyll plugins a little manual work is needed.
Read more - Dec 14, 2016
HowTo: Fail2Ban and custom filters
The first time I encountered Fail2Ban, and found it to be a useful tool, was when ransom malware has started to appear on client machines. Now there was a real risk the malware would propagate to the cloud storage platform. Fortunately the active malware Locky would place signature files and unique file extensions for encrypted files. With a tool like Fail2Ban we are able to monitor the webserver traffic for incriminating file uploads by the meta data, e.g. file names.
Read more - Dec 13, 2016
HowTo: Fix out-dated OwnCloud directory cache
When copying user accounts and files from one dedicated OwnCloud instance to another, I faced the problem of an out-dated directory cache. Some files could not be deleted and new files could not be created on the web interface. And the wordpress and apache logs strangely did not gave any indication of a problem. While not being a huge problem, but instead easily fixable, it still gave me some minutes to investigate.
Read more - Dec 12, 2016
HowTo: Let Fail2Ban automatically gather IP information
Fail2Ban allows the server administrator to have his access log files being automatically monitored for malicious behaviour. Often enough it’s interesting to see where the attack comes from geographically. And sometimes this helps identifying bugs with broken client software or wrong user authentication. Since my installation of Fail2Ban was unable to detect the public IP whois information, I tweaked the notification action command to load the missing data.
Read more - Dec 11, 2016
Snippet: easy firewall configuration with iptables
Since Debian, the distribution I feel home at the most, unfortunately has weak capabilities to manage iptables by default, I found the following script to be very useful. It runs at startup, is easily editable and can be extended without much effort.
Read more - Dec 10, 2016
Fork: Paper Page - Paper Flow (WordPress Theme)
In order to give the Paper Page website template a little spin, I decided to implement it as a WordPress theme. That way the content and template management will be easily achieved. And here it is: Paper Flow.
Read more - Dec 9, 2016
HowTo: Use Fail2Ban with apache for security
Fail2Ban is a great tool for linux to monitor log files of various programs and look for malicious attempts from attackers. Once an illicit request or action is registered or it exceeded a threshold in number, the IP address will get banned for a defined period of time, making it harder for an attacker to continue the system penetration. This short tutorial will give you a quick introduction for setting it up.
Read more - Dec 8, 2016
Snippet: Find duplicate files on linux
Once in a while a client comes by and asks for help with their duplicate files on the cloud storage platform. This happens especially often, when users manage their backups on their own without proper introduction or training. Then you’ll face files over files, scattered everywhere on the client’s storage, with uncertain timestamps and no meaningful user logs. That’s when the following shell script might come in handy.
Read more - Dec 7, 2016
HowTo: Change the Java Runtime Environment of Tomcat
When working with Debian the default repositories often only provide software versions of older age. That’s why as of today the Tomcat server will be only distributed with Java 7. And if you are required to use a more recent version of this programming language, you’ll need to tell Tomcat which binary to use.
Read more - Dec 6, 2016
Docker: load-postgis
I’d like to introduce a little container I created, load-postgis. It loads PostgreSQL database backup files from a local directory and restores its content, with special respect to geographic information systems.
Read more - Dec 5, 2016
Update: spatial.election 2.0
When I revisited my old spatial.election uni project, I faced several issues while trying to start it on modern versions of Java, PostgreSQL and Tomcat. I seized the opportunity to give it a major update and fix some old bugs.
Read more - Dec 4, 2016
Snippet: Piping a process I/O with Bash
While I worked on my OpenTTD container, I came to the challenge of wrapping a process for initial and final input and output, and temporarily guarding it from interrupt signals. This is my solution.
Read more - Dec 3, 2016
Docker: openttd
- Dec 2, 2016
Revisited: spatial.election will return in 2017
In less than a year, there will be the next elections for the Bundestag in Germany. Again we will face interesting political outcomes and changing trends on the level of country, state and city, even district. Thanks to the wonders of the World Wide Web, we can acknowledge statistics to almost anything in high definition. In a little web project I did some years ago, I examined political, social and economical data of districts in Germany with regard to spatial properties and the results of the federal election in 2013: spatial.election
Read more - Dec 1, 2016
New: website stub - Simple Page
Taken from a little side project for a client who just wanted a simple website without any heavy requirements, I want to give you the little template engine I created and more importantly the static HTML approach I exercised: Simple Page
Read more - Dec 1, 2016
New: website stub - Paper Page
Another little, personal web project yielded the need for a gimmicky site. Especially on mobile devices the “touch” feature can bring additional aspects to the usability. I liked the idea of turning pages, that’s why I forked botelho/flipboard-layout in 2014. I did some digging, and here it is again: Paper Page.
Read more - Nov 30, 2016
Meta: Self-hosted comments with Isso
Communication on a blog doesn’t inevitably have to be unidirectional. More than once I found solutions to my tech problems in the comments section of a related thread, thanks to popular search engines. Having a static website usually means embedding a third-party commenting service, most often Disqus. But there is an alternative: Isso.
Read more - Nov 29, 2016
Meta: Starting a blog
fishi0x01 encouraged me to start a developer blog. Thanks to him, I shall now be able to write down some thoughts, show difficulties I face during development and explain their solutions. It will also help me to keep track of progression on private projects, as well as announce their improvement and promote upcoming releases.
Read more
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