Schlomo Schapiro

Today I realized that for me it easier to create a small package than to copy a single file. The example is glabels-schlomo , a Debian package I created just now to store extra gLabels templates for the label sheets that I use at home. The motivation was that I spend half an hour looking through old backups to find a template definition that I had not copied over when I reinstalled my Desktop. Creating the package took another half an hour and now I can be sure that I won't forget to copy that file again. And I will also have the template definition at work in case I need to print a sheet of labels there. If you also feel that packaging is better than copying then feel free to use this package as a template for you own stuff. It contains a Makefile and uses git-dch to automatically build a DEB release from the git commits.

How many log levels do you know? How many log levels are actually useful? At Relax and Recover we had an interesting discussion about the use of the WARNING log level. I suddenly realized that in a world of automation, I need only two log levels: ERROR and everthing else. ERROR means that I as a human should take action. Everything else is irrelevant for me. So far for the user side. As a programmer the choice of log level is sometimes much more difficult. As a programmer I might not want to decide for the user if some problem is an ERROR or not. The obvious solution is to issue a WARNING in an attempt to shed the responsibility of making a decision. But in an automated world that does not help me as an admin to run the software better. WARNINGS for most cases only create extra manual work because somebody needs to go and check some log file and decide if there actually is a problem. I would rather have the software make that decision and I would be happy to fix or readjus...

Last week I attended the Multikonferenz Software Engineering & Management 2015 in Dresden hosted by the Gesellschaft für Informatik : My topic was Test Driven Development, but I had to rework my original talk to fit into 20 minutes and to be much less technical. As a result I created a completely new  fast paced talk which draws a story line from DevOps over Test Driven Infrastructure Development into Risk Mitigation: SE 2015 DevOps Risk Mitigation - Test Driven Infrastructure from Schlomo Schapiro The conference is very different from the tech conferences I usually attend. First, I really was the only person in a T-Shirt :-/. Second, I apparently was invited as the "practitioner" while everybody else was there to talk about academic research, mostly in the form of a bachelor or master thesis. As much as the topics where interesting, as little was there anything even remotely related to my "practical" work :-( I still find it interesting to bet...

After many years of abstinence I went back to visit the CeBIT today. And actually enjoyed it a lot. It is funny to see how everything is new but nothing changed. From the oversized booths of the big players like IBM and Microsoft to the tiny stalls of Asian bank note counting machine vendors. From the large and somewhat empty government-IT-oriented booths to meeting old acquaintances and friends. But there are also several notably new things to see: For example Huawei shows itself being an important global player with a huge booth next to IBM. I managed only to visit a third of the exhibition but it was more than I could absorb in a single day. Nevertheless, my missing was accomplished with giving a talk about “ Open Source, Agile and DevOps at ImmobilienScout24 ”. The talk is much more high-level than my usual talks and tries to give a walk through overview. There were about 60-80 people attending my talk and the questions showed that the topic was relevant for the audience...

Relax and Recover  is the leading Open Source solution for automated Linux disaster recovery. It was once the pride of my work and is now totally irrelevant at my current job at ImmobilienScout24 . Why? Simply because at ImmobilienScout24 we invest our time into automating the setup of our servers instead of investing into the ability to automatically recover a manually configured system. Sounds simple but this is actually a large amount of work and not done in a few days. However, if you persist and manage to achieve the goal the rewards are much bigger: Don't be afraid of troubles, based on our automation we can be sure to reinstall our servers in a very short time. The following idea can help to bridge the gap if you cannot simply automate all your systems but still want to have a simplified backup and disaster recovery solution: Inject a layer of automation under the running system. The provisioning and configuration of the automation layer should be of cour...

Apache HTTPD 2.4 has a very useful new feature for large deployments: Replacing the remote IP of a request from a request header , e.g. set by a load balancer or reverse proxy. Users of Apache HTTPD 2.2 as found on RHEL6 can now use the backport found on  https://github.com/ImmobilienScout24/mod_remoteip-httpd22 . I pulled this backport together from various sources found on the Internet and "it seems to work". Working with C code ( which I did not do for 14 years !) tought me again the value of test driven development and modern programming languages. Unfortunately I still can't explain a change like this without a lot of thinking: You can easily build an RPM from the code on GitHub. The commit history shows the steps I had to undertake to get there.  Configuration is as simple as this: LoadModule remoteip_module modules/mod_remoteip.so RemoteIPHeader X-Forwarded-For RemoteIPInternalProxy 10.100.15.33 with the result that a reverse proxy on 10.100.15.33 can s...

2 years ago I wrote about creating a repository for DEB packages with the help of reprepro . And since then I suffer from the complexity of the process and cumbersome reprepro usage: Complicated to add support for new Ubuntu version which happens every 6 months Need to specifically handle new architectures I actually don't need most of the features that reprepro supports, e.g. managing multiple repos in one or package staging This week I realized that for there is a much simpler solution for my needs: apt-ftparchive . This tool creates a trivial repo with just enough information to make apt happy. For my purposes that is enough. All what I want from a DEB repo is actually Work well with 50-500 packages Easy to add new Debian/Ubuntu/Raspbian versions or architectures Simple enough for me to understand GPG signatures It turns out that the trivial repo format is enough for that, it makes it even simpler to add new distro versions because the repo does not contain a...

The guest session  is a very important feature of Ubuntu Linux . It makes it very simple to give other people temporary computer or Internet access without compromising the permanent users of the computer. Unfortunately the separation is not perfect, the guest user can actually modify critical configuration settings on the computer and even access the files of the other users, if they don't take precautions. The following scripts and files help to lock down the guest session so that no harm can be done. How It Works The guest session is actually a feature of the LightDM Display Manager that is used in Ubuntu and in Xubuntu . The guest session is enabled by default. When a user chooses a guest session the following happens: LightDM uses the  /usr/sbin/guest-account script to setup a temporary guest account. The home directory is created in memory (via tmpfs ) and can occupy at most half the RAM of the computer. Optionally, /etc/guest-session/prefs.sh is i...

A site to site VPN is the standard solution for connecting several physical data center locations. Going to the Cloud, the first idea that comes to mind is to also connect the Cloud "data center" with a site VPN to the existing physical data centers. All Cloud providers offer such a feature. But is such a VPN infrastructure also a "good idea"? Will it help us or hinder us in the future? I actually believe that for having many data centers a site VPN infrastructure is a dangerous tool. On the good side it is very convenient to have and to set up and it simplifies a lot of things. On the other side it is also very easy to build a world-wide mesh of dependencies where a VPN failure can severly inhibit data center operations or even take down services. It also lures everybody into creating undocumented backend connection between services. The core problem is in my opinion one of scale. Having a small number (3 to 5) of locations is fundamentally different from h...

I recently got myself a new printer, the HP Officejet Pro X476dw . A very nice and powerful machine, it can not only print double sided but also scan, copy and send faxes. And of course it has very good Linux support, thanks to the HP Linux Printing and Imaging Open Source project. On my Ubuntu 14.10 desktop everything is already included to use the printer. However, the first printouts where very disappointing. They looked coarse and ugly, much worse than prints from my old HP LaserJet 6 printer. After overcoming the initial shock I realized that only prints from my Ubuntu desktop where bad while prints over Google Cloud Print where crisp and good looking. So obviously something has to be wrong with the printer drive on Ubuntu! After some debugging I was able to trace this down to the fact that by default CUPS converts the print job to 300 dpi PostScript before giving it to the hp driver, as it shows in the CUPS logs: D [Job 261] Printer make and model: HP HP Officej...

Since ImmobilienScout24 decided to migrate to a public cloud I have been busy looking at various cloud offerings in detail. Amazon Web Services  (AWS) has a special feature which is interesting: Amazon Linux is a fully supported, "RHEL like", RPM-based Linux distribution. While not beeing a true Red Hat Enterprise Linux clone like CentOS or Scientific Linux (which is the standard OS for the ImmobilienScout24 data centers), it is derived from some Fedora version and comes with a nice choice of current software. To me it feels like "RHEL +" because so far all our internal stuff worked well but a lot of software packages are much newer than on RHEL 6 or RHEL 7. The 2014.09 release  updated a lot of components to very recent versions. On the other hand, we also found packages missing from Amazon Linux, most notably desktop-file-utils . This package is required to install Oracle Java RPMs . I found a thread about this on the AWS Forums and added a request fo...

Update:  Read my (German) conference report on heise developer . Last week I was at the DevOps Days Berlin 2014 . This time at the Kalkscheune , a much better location than the Urania from last year. With 250 people the conference was not too full and the location was also well equipped to handle this amount. Proving DevOps to be more about people and culture, most talks where not so technical but emphasized the need to take along all the people on the journey to DevOps. An technical bonus was the talk by Simon Eskildsen about " Docker at Shopify " which was the first time that I heard about a successful Docker implementation in production. Always good to know is the difference between effective and efficient as explained by Alex Schwartz in " DevOps means effectiveness first ". DevOps is actually a way to optimize for effectiveness before optimizing for efficience. Microsoft and SAP gave talks about DevOps in their world - quite impressive to see DevOps...

One full week of Python power is almost more than one can take, but I missing it would be even worse. This was my first EuroPython and with 1200 participants a big upgrade compared to the previous 2 PyCon.DE events in which I participated. The location ( Berlin Congress Center ) deserves kudos, along with the perfect organization. The Wifi worked really well (except for a WAN problem on Tuesday which was fixed quickly) and everybody loved the catering. They even had kosher, helal and vegan food (preordered), which is highly unusual for German conferences. Most amazing was the video crew who managed to upload all videos in about one hour after a talk was given. I managed to give three talks: DevOps Risk Mitigation How we use Test Driven Infrastructure at ImmobilienScout24 as part of our general automation to reduce the risk of giving everybody access everywhere. ( Access Slides or Watch Video ) YAML Reader Lightning Talk about the yamlreader Python library, which provide...

iPXE is a lesser known Open Source  PXE boot loader which offers many interesting features: boot from a web server via HTTP and HTTPS boot from remote block device over  iSCSI , FC , FCoE , AoE SAN boot from VLAN , WiFi, WAN, Infiniband control the boot process with a script user interaction with menus and login prompts display images and splash screens replaces NIC firmware or chain load via PXE Talk & Article Since iPXE plays a role in the ImmobilienScout24 boot automation I gave a talk about it at the LinuxTag 2014 . The talk is half an hour long and gives a quick introduction into iPXE. It covers build, configuration & scripting and shows how to develop boot scripts in iPXE with a very short feedback cycle. Download the  slides to the talk  and the  audio recording  as a podcast. At the conference the German Linux Magazin became interested in the topic and asked me to write an article about iPXE: Der vielseitige N...

I do a lot of pair working and many times I connect a large TV or projector to my laptop for others to see what I am doing. Unfortunately the display resolution of my laptop never matches that of the other display, and Linux tends to choose 1024x768 as the highest compatible resolution. This is of course totally useless for doing any real work. My preferred solution for this problem is to use X scaling to bridge the resolution gap between the different screens. Since none of the regular display configuration tools support scaling, I ended up typing this line very often: xrandr --output LVDS1 --mode 1600x900 --output HDMI3 --mode 1920x1080 --scale-from 1600x900 Eventually I got fed up and decided to automate the process, the result is automirror , a little Bash script that automatically configures all attached displays in a mirror configuration. automirror is available on  https://github.com/schlomo/automirror . Typical Use Cases Connecting a Full HD 1920x1080 disp...