Docker Shell Corner Cases

2017-01-18 Ronny Trommer
During work building Docker executables, I ran in an interesting corner case. Fortunately the Docker IRC channel helped me to investigate with special credits to Ravensoul. When you build a container as an executable you can use the ENTRYPOINT for your binary to execute and CMD as a default overwritable argument. In most cases the CMD is the --help argument to provide a useful default behavior in case you just run the container without anything specified. Continue reading

IPv6 and Monitoring

2016-03-19 Ronny Trommer
We are all happy when we are able to get IPv6 connectivity for our new servers. In case the network is provided by someone else and some kernel settings you can get in some tricky situations. With IPv6 there are so many addresses your Laptop and Mobile can have a unique public IPv6 address forever - pretty cool huh? The downside is, it would be pretty easy to trace every connection you ever do back to your device - this really not what you want! Continue reading

Investigate file descriptor issues

2014-11-07 Ronny Trommer
If you run a centralized monitoring system in large environment you can run in some issues regarding file descriptor limits. Linux gives you very detailed information in the kernel control and information center in /proc. The soft and hard limits have effect for file and network sockets, which can end up in a too many files open exception in OpenNMS. The default values for soft and hard limits can be checked with Continue reading