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Multi-Arch Docker Images sind eine tolle Sache: Benutzer Eurer Images ziehen automatisch die für Ihre Architektur passende Version Eures Image – ob AMD64, ARM64 oder ARM32. Normalerweise muss man Docker Images auf der Architektur bauen, auf der sie später auch verwendet werden. Durch die Verwendung des Emulators QEMU ist es jedoch möglich, auf einer AMD64-Architektur für alle anderen Zielplattformen mitzubauen. Kombiniert mit der Auto-Build-Funktion des Docker Hub ist das eine prima Arbeitserleichterung....

If you’re using Jenkins as your Continuous Integration (CI) tool and Docker to build self-contained images of your application, you may ask yourself how to automatically build Docker images during Jenkins’ build job. Here’s how I did it – with Jenkins running in a Docker container itself. So far, I’ve used the official Jenkins Docker image (the one based on Alpine). I’ve tried some of the Docker plugins for Jenkins available out there....

I’m using NGINX in a Docker Container as a front-end HTTP(s) Webserver, performing SSL termination and proxying incoming requests to various other Docker Containers and VMs. Now that I’ve switched my certificates to Let’s Encrypt, I wondered how to integrate EFF’s CertBot (which is recommended by Let’s Encrypt) with my setup. Here’s how I did it. First, I’ve added two new volumes to my web-front-end’s Docker Compose File: version: '2' services: webfrontend: container_name: webfrontend [....

Some years ago, I’ve used TrueCrypt to create encrypted containers for storing sensitive files. However, TrueCrypt is nowadays considered insecure and I’m on macOS Sierra 10.12 now – time for another solution. Luckily, macOS has integrated means for creating encrypted containers and saving sensitive information in it. You don’t need any additional software for this. As far as I know, this solution also works for previous versions of Mac OS X, like Mac OS X 10....

Over the weekend I’ve been looking around for a free service which monitors my websites. My requirement was that I want to be able to monitor both HTTP and HTTPS sites, I need support for authentication and the monitoring service should be able to check if a specific keyword exists within the watched site (instead of just assuming that a HTTP Status Code 200 is okay). Furthermore, I needed notifications in case of downtimes (Email and Pushbullet is fine for me)....

On my MacBook with Mac OS X 10.11 (El Capitan) and Docker 1.12.0, Docker did not read manually set DNS entries from the /etc/hosts file. When I executed “docker push” for example, this resulted in “no such hosts” errors: Put http://shuttle:5000/v1/repositories/webfrontend/: dial tcp: lookup shuttle on 192.168.65.1:53: no such host On Mac OS, Docker is running in a host container itself. Thus, you’ll have to add DNS entries to the container’s /etc/hosts file....

For more than 2.5 years, I’ve now been running FHEM with several HomeMatic sensors and actors. Using the HM-CFG-LAN Configuration Tool as an I/O interface between FHEM and the HomeMatic devices, this setup has been running smoothly most of the time. The configuration was a bit tricky now and then, but it worked. However, OpenHAB seems to become a really good choice. Version 2 is currently available as Beta 3. It features a modern web interface and an easy-to-use extension manager....

Today I changed the accessibility of my blog from HTTP (unencrypted) to HTTPS/SSL. My blog is running WordPress behind an nginx proxy server. However, while the pages themselves loaded successfully from HTTPS, the embedded static resources like JavaScripts, Images, CSS files etc. did not. Here’s how I fixed it. The cause of this issue is that WordPress doesn’t seem to detect the original protocol scheme (HTTPS) correctly when running behind a proxy....

Several months ago, I wrote a blog post about reducing a PDF file’s size. Since then, I’ve used that technique many times. However, you may want to control the DPI (dots per inch) even more specific. Here’s how to do it: gs -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -dCompatibilityLevel=1.7 \ -dDownsampleColorImages=true \ -dDownsampleGrayImages=true \ -dDownsampleMonoImages=true \ -dColorImageResolution=120 \ -dGrayImageResolution=120 \ -dMonoImageResolution=120 \ -sOutputFile=output.pdf input.pdf Hint: This also works on MacOS. Just install GhostScript using Homebrew:...

IPv6 aimed to make Network Address Translation (NAT) obselete as there are so many addresses available that every single device can have its own worldwide unique IPv6 address. However, even with IPv6, using NAT is a very simple way to get your devices behind a Dell SonicWall connected to IPv6 services on the internet. In contrast to going without NAT, all the devices behind your SonicWall will emerge under the SonicWall’s IPv6 address....