Category Archive: Computers

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 09

Abusing Awk

Almost ashamed to admit I did this, yet it’s still kinda cool. I use awk for a lot of commandline parsing; I learned it back in 1989…. before perl was much of a thing. For some problems, awk “just works”. So I was wanting to count the number of instances of ‘A’ in a collection …

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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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Mar 23

Shrinking Docker Images

Size does matter. Docker images can become quite large as each RUN generates a new layer which becomes part of the image, even if it’s not in the final container. This wastes disk space and network bandwidth. The following are some steps for shrinking the size of a docker container in which builds have been …

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Mar 22

Docker Cleanup

After a time, Docker containers and images build up and can eat disk space. Failed docker build invocations can leave a lot of artifacts behind. The following commands can help. Many of them say ‘not all containers could be removed’; this has to do with the header from docker ps. Usually this can be ignored. …

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Mar 19

Pi on a Pi Followup

The particular algorithm used in calculating Pi is one which converges to Pi as you add terms; it’s not calculating out to a number of digits, although I might try that one as well at some point. Here’s the output from a run; it’s interesting how it gets closer and closer, but… Another interesting thing …

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Mar 17

Lost in a Maze of Twisty Little Java Classes: How often is “infinite scalability” and extensibility really needed?

But look, you found the notice, didn’t you? Yes yes I did. It was on display at the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying Beware of the Leopard. — Mr. Prosser and Arthur Dent, The Hitchhiker’s Guide to the Galaxy While digging through …

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Mar 17

Pi on a Pi for Pi Day

What better thing to do on Pi Day than to calculate Pi? I figured while I’m at it, I might as well do some performance testing of the Raspberry Pi 2 B. I’m using the following for my comparisons: Host Description Bits Pi 2B Quad Core, 900 MHz ARM 7, 1G ram 32 Pi B+ …

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