christoph ender

about me

I'm a freelancer working on IT operations, networking and development. I've been doing a great variety of projects, from the development of web shops over private banking frontends up to the development of a complete clinical trial project system. Over many years, I've been using and gained experience in the following technologies:

technical experience

• Operations
  Monitoring utilizing icinga[web]2, high availability with VRRP/keepalived, loadbalancing, centralized logging using Grafana Loki and Promtail, network planning and implementation scaling all the way from on-premise-LANs to entire cloud-based infrastructures utilizing OCI, AWS, Hetzner or other cloud providers.
• Networking
  IPv4/IPv6, Wireguard, OpenVPN, IPSec via StrongSwan and various hardware implementations, DHCP using legacy ISC DHCP or new ISC Kea DHCP, radvd, DNS using bind/unbound or others.
• E-Mail
  Implementing full fledged high-availability SMTP-/IMAP-Servers using postfix, dovecot with dsync-based replication, Amavis, SpamAsassin, DKIM, DMARC, SPF, PostSRSd and Sieve.
• Languages
  JavaScript, Java, C, PHP, Visual Basic .NET, Perl, SQL.
• Databases
  Oracle 11g/19c, PostgreSQL, MySQL/MariaDB, InfluxDB.
• Systems
  Linux – Debian, RedHat, Oracle linux – on Intel and various ARM-based systems – Raspi etc., macOS, Windows and Windows Server.
• Markup Languages
  HTML, XML, CSS, XSLT, XSL-FO, XSD, SVG, Markdown.
• Other Technologies
  Docker / Containerization, traefik, ansible, Node.js, btrfs, zfs, LVM, LUKS, SSH, Grafana, Loki along with Promtail, Syslog, Apache, Kemp Loadmasters, CalDAV- and CardDAV-systems using DAViCal, jQuery, CMake, Ant, Apache Tomcat, Servlets, JDBC, JUnit, Cocoon, JMX, FOP, Samba, TeX/LaTeX, EWS, OpenAuth, NTP, nfs, Bitwarden, OpenID, Procmail, imapsync, Dynamic DNS, GnuPG.
• Shells
  bash, Powershell, zsh.
• Version control
  git, svn, cvs.
• Basic knowledge
  C++, C#, Shopware, M4, nginx, Informix, MQTT, nroff/troff

professional experience

• terminland
  Terminland is the leading provider for online-scheduling systems in Germany. I'm supporting them by working on database, network and loadbalancing operations as well as in development.
• pegasus spiele
  Pegasus Spiele is a german game publishing and distribution company where I've been working on online shop functionality and IT operational management, from backup systems over Postfix-based newsletter systems to ecommerce-related data synchronization since 2000.
• easyclin
  Over several years from 1999 to 2013 I've implemented a validated clincal trial management system for Synapcon Ltd. along with the entire IT operational management, from Postfix-based company mail server to a fail-safe server environment in two separate data centers.
• tu darmstadt and deutsche telekom
  I've been doing research for the foundations of a recommendation system for TU Darmstadt and Deutsche Telekom AG in 2009.
• dresdner bank
  In 2002 and 2003, as well as from 2005 to 2006 I've been supporting the Dresdner Bank AG – now Commerzbank AG – in the implementation of a private banking frontend.

other projects

• fizmo
  fizmo is an interpreter for Z-Machine programs. This virtual machine is able to run old, text-based games, as well as modern interactive fiction.
• sherlock-holm.es
  I'm interested in typography, fonts, layout and things related, resulting in a typeset version of the Sherlock Holmes canon at sherlock-holm.es.