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November 10 2020 Nextcloud, Enhancer, ARIA, Agile, INDI and backup

John R Hudson
Posted on November 13, 2020
( 5 minute read )

Brian has swapped from Digital Ocean to Amazon because he only needs a web server and not a website but he was puzzled by the output of free -m which suggested that he had very little free memory. David explained that the Linux kernel uses whatever memory there is for cache and so will reclaim memory from cache if it needs more than the free memory available.

Brian then demonstrated his Nextcloud set up. He also mentioned Firefox Enhancer for Youtube which David proved worked. Hitherto, Brian had used Pi-hole to get rid of banners. It was noted that the RIAA has persuaded GitHub to disable the youtube-dl repositories.

Brian then shared some problems he was having with the wi-fi; David wondered if it was a firmware buffer bloat bug and whether he should try rebooting the rooter; in the course of exploring this John mentioned using nmtui, the command line interface for NetworkManager, and Brian discovered that NetworkManager had not been installed.

Darren shared some topics from his OU software engineering course; one aspect is web authorship for which he had been looking at John’s HTML webpage and the ARIA guidelines; John said that, bearing in mind that it is 25 years since the passing of the 1995 Disability Discrimination Act, by the end of September 2020, all government supported organisations were supposed to ensure that their websites complied with the Web Content Accessibility Guidelines (WCAG) 2.1 but he wasn’t sure that all did.

Another topic Darren is studying is Agile software development, looking at client requirements, use cases and stories, or users’ accounts of what they want. John commented that many of the issues are similar to the issues he was addressing on his course in 1987 when prototyping was in fashion. Though that appears to have disappeared, it could be argued that the Linux kernel project is the most successful example of prototyping.

Bernard demonstrated using the Instrument Neutral Distributed Interface (INDI) with a virtual telescope; he demonstrated how it might be started and then instructed to take a photo; the image it takes is in Flexible Image Transport System (FITS) format. INDI will work with any device that has a driver for it. He is hoping to adapt the code for the robotic telescope.

The code uses a fairly new feature of Python: async. Normally, when you start a new thread, Python shares the load synchronously; using async within a loop returns to the loop if the function cannot be run. Using it in a single thread in a single process avoids spawning multiple processes.

Brian asked about writing a timer in Python and Bernard recommended the sched module.

Brian mentioned a kernel upgrade which had broken things prompting a tirade from David about distributions that add backports to kernels rather than leaving them alone.

Brian mentioned that he had set up Linux Mint Timemachine for a friend but found that it took too much space. Looking for backup tools, the following were recommended:

In response to a comment about managing multiple audio streams, OBS Studio was recommended.

Brian mentioned the Enigma project at Bletchley Park and John commented that the more interesting one was the cracking of the Lorenz cipher by Bill Tutte and the building of Colossus by Tommy Flowers, the Post Officer engineer, which had been covered in a BBC Timewatch programme from 2011, recently re-broadcast during lockdown.

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