Laur IVAN

Docker Exec Path-based Commands

Posted by in IT, Tutorial

TL;DR: Use sh -c “command with arguments” I’ve tried to execute

in order to see the size used by a container’s logs. Unfortunately, this resulted in an error along the lines: du: C:/Program Files/Git: No such file or directory This means that my git bash prompt interpreted the / itself. In order to get around this limitation, you need to run:

HTH, A little experiment: If you find this post and ad below useful, please check the ad out :-)

Fix *standard_init_linux.go:XXX: exec user process caused “no such file or directory”* Error

Posted by in IT, Tutorial

TL;DR: Use dos2unix While switching from Ubuntu to Alpine images, I’ve encountered the fillowing error: standard_init_linux.go:195: exec user process caused “no such file or directory” Quite unfortunate, because the script stayed in the same spot and only the image changed. After reading a bunch, I figured that it’s the fact that I’m editing on Windows and Alpine doesn’t seem to interpret #/bin/sh properly – adding a ^M :). The solution is to either fix the script locally or to format it as part of the docker build process. I chose…read more

Initialise Python with GoCD

Posted by in IT, Tutorial

Following the deployment of a python-aware agent, we can start creating a pipeline. The first stage would be to: Clean up any previous data Create a virtual environment for python Install all dependencies from a requirements.txt file in our project Note: we assume the global pipeline settings and the Materials are properly set up (e.g. out project will be checked out in ./project). Since the above operations must be executed in order, I’ve set up a Setup stage with a job named virtualenv. The job has three tasks: rm virtualenv…read more

Create a Python-friendly GoCD Agent in Docker

Posted by in IT, Tutorial

I’ve got two requirements to make GoCD useful: Run both the server and agent(s) in Docker Make it python-friendly Fortunately, GoCD offers Docker images (and Dockerfiles) for both, so it’s just a matter of extending it:

Unfortunately, pip is not quite adequate, so we re-install it from source. In the Dockerfile we add:

Now we have a fully functional Docker file capable of building python applications and we can actually build the image. In the directory where we have the Dockerfile, execute:

Then, you can run it…read more

Allow Docker Container Access Behind Proxy

Posted by in IT, Tutorial

In the previous post, I’ve described how to build an image when you’re behind a proxy. Now, if your container needs access to the internet for e.g. downloading python dependencies, you’ll need to give it explicitly. The way to do it is via -e parameter (environment) of docker run. You can either make it verbose, or you can build an alias:

Then, you can just execute:

HTH, A little experiment: If you find this post and ad below useful, please check the ad out :-)

Show What’s on Swap in Linux

Posted by in IT, Tutorial

If you find your machine running sluggish, it might be the case that you have too many things running and it’s hitting the swap. You can check how bad (or good) things are with htop, but it won’t tell you which process is sitting on swap. To find out, I’ve cooked up a tiny script:

It will look in /proc/[PID]/status and get the VmSwap field. Then, it’ll print it out along with the PID and the command line (from ps -ax). Note: This is a rather crude script and…read more

Fix Jenkins POM Freezer
“Wrong Relative POM” Error

Posted by in IT, Tutorial

If you get a build error in Jenkins like:

Then you have a POM freezing issue with the parent POM. I.e., the Jenkins plugin has failed to freeze the POM version from a 1.0-SNAPSHOT to an actual 1.0-6034-79. A cause can be the plugin expects a certain sequence of tags in the POM and doesn’t find it. In my case, the initial configuration was:

and the expected configuration would be something like

Note the sequence group – artifactId – version. HTH, A little experiment: If you find…read more

Make a Shell Script with Arguments (Native)

Posted by in Software, Tutorial

I was building a bash script and I needed several arguments to make it more versatile (e.g. dry-run). The list of parameters was: help as -h or –help dry run ad -d or –dry-run to go through the motions without actually executing commands keep last N images ad -k num or –keep num to keep last N images (default 5) As one can see, none of the parameters are compulsory and have default values:

The snipped taking care of my input parameters is:

The idea is that we…read more

Handler for Global Logger in Python

Posted by in Software, Tutorial

While writing a command line tool, I’ve stumbled upon a strange situation: Some logs were written to a file while some others were printed to console. Quite annoying, particularly since every module I use has its own logger via logging.getLogger(__name__). After some investigation I found out you can access the global logger via logging.getLogger() (note the lack of parameters). So, my new setup is:

Simple. HTH, A little experiment: If you find this post and ad below useful, please check the ad out :-)

DRF: What is ‘source’ in Fields?

Posted by in Software, Tutorial

For a couple of days I’ve been trying to de-serialise a JSON to a model. My problem is the model and the JSON have different fields, mainly to keep the model pythonic and independent of a specific JSON source. So… I’ve been trying to use the source parameter for each Field in my serialiser to map to the JSON. E.g. if my Django Model field would be named timestamp and my JSON would be named time, I would have a serialiser Field like this:

THIS IS WRONG! It’s actually…read more