JJJ's Blog

Weblog of John James Jacoby

17 Rules

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Build modular programsWrite readable programsUse compositionSeparate mechanisms from policyWrite simple programsWrite small programsWrite transparent programsWrite robust programsMake data complicated when required, not the programBuild on potential users' expected knowledgeAvoid unnecessary outputWrite programs which fail in a way that is easy to diagnoseValue developer time over machine timeWrite abstract programs that generate code instead of writing code by handPrototype software before … [Read more...] about 17 Rules

19 Lessons

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Every good work of software starts by scratching a developer's personal itch.Good programmers know what to write. Great ones know what to rewrite (and reuse).Plan to throw one [version] away; you will, anyhow (copied from Frederick Brooks's The Mythical Man-Month).If you have the right attitude, interesting problems will find you.When you lose interest in a program, your last duty to it is to hand it off to a competent successor.Treating your users as co-developers is your least-hassle … [Read more...] about 19 Lessons

Raspberry Pi 4, Ubuntu 20.04, PoE Hat Fan Control

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I recently acquired an 8Gb Raspberry Pi 4 and promptly installed Ubuntu 20.04 on it to see how it worked. Right away, I was excited that the PoE Hat worked and that it booted without any problems, except that the fan on the Hat was no longer controllable the way that it used to be. It appears that the old way of using config.txt and friends to override those settings no longer works. Here's what you need to do: Put this in it to start with, and tweak as needed for your situation: … [Read more...] about Raspberry Pi 4, Ubuntu 20.04, PoE Hat Fan Control

macOS Disk Utility “Operation cancelled”

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When trying to use Disk Utility to make a backup of one of my Raspberry Pi's, I was repeatedly seeing an error that was causing my backup to fail. Operation cancelledDisk Utility Not particularly helpful. For me, the fix involved setting the Disk Utility application to have Full Disk Access inside macOS System Preferences, under Security & Privacy, and then Privacy. Once I did this, everything started working again! 🥳 … [Read more...] about macOS Disk Utility “Operation cancelled”

Update GitLab signing key

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At the beginning of April, GitLab updated their repository signing key. If you try to update, you will see an error during sudo apt update : W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.gitlab.com/gitlab/gitlab-ee/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3F01618A51312F3F W: Failed to fetch … [Read more...] about Update GitLab signing key

Raspberry Pi PoE Hat Fan Control

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I noticed yesterday that the fans on the PoE Hat of my Raspberry Pi 4's were behaving strangely. They were both kicking on based more on time than temperature, even though neither of them seemed that hot. You can check the temperature via the command line like this: /opt/vc/bin/vcgencmd measure_temp And you'll get something like: temp=42.0'C That didn't seem hot enough to me to warrant the fans going full blast, and it doesn't help that these fans have a high-pitched whine to … [Read more...] about Raspberry Pi PoE Hat Fan Control

Thoughts on UDM Pro Market Fit

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A lot of folks online are being critical of Ubiquiti about releasing the UDM Pro with the features it has and the hardware it’s configured with, because they feel it does not have the same obvious market fit that most of their other hardware has always had prior to it. I believe that the UDM Pro makes big economic sense for Ubiquiti, and will likely carry their “Gen2” products onwards to be their most successful lineup so far. The UDM Pro is priced competitively ($379 USD) against their … [Read more...] about Thoughts on UDM Pro Market Fit