Category Archive: gotchas

Feb 11

Docker: Could not find container for entity id

I had an instance where the docker filesystem ran out of space. After cleaning up with docker rm and docker rmi, I got:

I followed iwidanalage‘s suggestion from “Creating fail with Could not find container for entity id after upgrading to 1.9.0 · Issue #17691 · docker/docker”

After this, it worked.

Sep 21

F5 LTM Monitoring and Wildfly

TL;DR The F5 BigPipe LTM uses HTTP/0.9 to send its HTTP monitoring requests by default. Wildfly 9.0 does not like this; moving to a monitor request of HTTP/1.1 fixed the problem. Caution: LTM 10.2.x and 11.x do not append a CR/LF to the end unless you are using Basic Authentication. This is contrary to previous …

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Sep 18

OBS for Videos

I recently discovered a really interesting tool for producing videos of screen captures, optionally with webcam inserts. It’s called Open Broadcaster Software and it works on Linux, Windows, and there is a beta version for Apple OSX. It seems that it was originally intended for streaming to websites, but it has a lot more features …

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Sep 07

Troubleshooting MicroSD Card Problems

The Computer employs Troubleshooters, whose job is to go out, find trouble, and shoot it. — Paranoia While re-imaging the MicroSD cards for my cluster, I ran into a few issues — nothing insurmountable, but I figured that I would share them to help others….. MicroSD cards generally come with an adapter to allow them …

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Apr 19

Docker Containers: Smaller is not always better

Generally smaller Docker containers are preferred to larger ones. However, a smaller container is not always as performant as a larger one. By using a (slightly) larger container, performance improved over 30x. TL;DR The grep included in busybox is painfully slow. When doing using grep to process lots of data, add a (real) grep to …

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Apr 12

Docker Commandline Arguments are Context Sensitive

TL;DR: Position of the commandline arguments matter. `-v` before `run` means something totally different than `-v` *after* `run`. More details below the link.

Apr 07

Cron the Eater of (CPU) Time

Note: This behaviour was observed on a Pi B+; it was not observed on a Pi 2. I happened to have top up while doing the bonded Nic test and noticed that the load was awfully high. Then the following popped up: Cron pretty much has the CPU pegged. Once I saw this, I wondered …

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Apr 06

Why it’s Important to use TLS with Docker Swarm

There is nothing wrong with your docker host. Do not attempt to adjust the picture. We are controlling transmission. If we wish to make it louder, we will bring up the volume. If we wish to make it softer, we will tune it to a whisper. We will control the horizontal. We will control the …

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Jan 13

It’s a Trap: Losing Faith in Protex

Protex snippet match does not behave as expected.

Jan 12

Part of what makes Open Source analysis “interesting”

You unlock this door with the key of imagination. Beyond it is another dimension: a dimension of sound, a dimension of sight, a dimension of mind. You’re moving into a land of both shadow and substance, of things and ideas. You’ve just crossed over into… the Open Source Zone. — Not Rod Serling Consider a …

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