Search Results: "Jonathan Dowland"

17 September 2022

Jonathan Dowland: Introducing Red Hat UBI9 OpenJDK runtime images

A few weeks ago we shipped the first RHEL UBI9-based OpenJDK container images. Universal Base Image (UBI) is an initiative where you can obtain, share and build upon official Red Hat container images without needing a Red Hat subscription. They're exactly the same base images that Red Hat products are built upon, composed entirely of Open Source software. Your precise rights are covered in the EULA. Nowadays we offer two flavours of images, the original style (now termed builder images) and leaner runtime images, which have a subset of the JDK, and no build tools like Maven, etc. We provide JDK11 and JDK17 for UBI9:
podman pull registry.access.redhat.com/ubi9/openjdk-11
podman pull registry.access.redhat.com/ubi9/openjdk-17
podman pull registry.access.redhat.com/ubi9/openjdk-11-runtime
podman pull registry.access.redhat.com/ubi9/openjdk-17-runtime
In comparison to the UBI8 images, we have done a lot of housecleaning. If you are curious as to exactly what we've changed, you can read the list of commits in this pull request. Perhaps most notable is a change in the way we tune the JVM's memory. In our existing images up to now, partially for legacy reasons, the container start up scripts interrogate the cgroups (v1) virtual filesystems to establish any memory limits imposed on the running container. From that, they calculated a percentage of the memory limit as an absolute value, and then ask the JVM to limit its heap to that calculated sum via the -Xmx flag. This dates back to a time when the JVM was not container aware. It now is, so for the UBI9 images we instead ask the JVM directly for the percentage we want using -XX:MaxRAMPercentage. We've also changed the default percentage from 50% to 80%, to better utilise the memory assigned to Java containers. One big advantage of this is the JVM is cgroups (v2) aware, and the legacy start up scripts we wrote are not. But another is reducing the amount of code we run in the start up scripts, easing maintenance and simplifying the containers as much as possible. Please give them a go, and let me (or us) know what you think!

15 September 2022

Jonathan Dowland: things I'd like to 3D print, revisited

Back in November I wrote up a list of 25 things I would 3D print. Let's revisit the list and see how things have developed. Stuff I won't print
  • Some kind of 45 leaning prong to dry bottles and flasks on
  • A tea tray and coasters
  • Small tins to keep loose-leaf tea in
It was pointed out to me that you can't safely print things to store food in with most materials, as their porous/layered nature facilitates the growth of bacteria. So, I'll rule out those items.
A vinyl record.
The size of the grooves in a vinyl record are smaller than conventional FDM printers can achieve. Things I've printed
a replacement prop arm/foot for my computer keyboard
Someone has modelled the exact part I need, and it worked great: https://www.printables.com/model/59132-lenovo-keyboard-kt-1255
replacement toy bolt replacement toy bolt
replacement bits for an Early Learning Centre Build It Deluxe Set
I was amazed to find that someone has already modelled one of these, too, and it worked beautifully: https://www.printables.com/model/79243-elc-build-it-compatible-bolt
Little kids trinkets. Pacman ghosts
The Pacman ghost family so far The Pacman ghost family so far
So far, I've tried to print useful, functional things, but on a few occasions I've printed a little Pacman ghost when testing printer calibration or similar. I've mostly used these models: https://www.printables.com/model/199425-pac-man-ghost-v2
  • Lego storage/sorters
  • DIY bits-and-bobs sorter/storage (nuts and bolts etc)
I learned about a Slicer setting sometimes called "Vase mode" and found this interesting system of modular drawers that are designed to be printed in Vase mode, so I gave them a go: https://www.printables.com/model/139570-fast-printing-modular-drawer-system-vase-mode I printed one and four drawers for it and gave it to my daughter. It might be used for sorting Lego, or possibly as a chest-of-drawers for a dolls house.
A free-standing inclined vinyl record display stand
https://www.printables.com/model/174711-vinyl-stand-for-kallax
A bracket to install a Gotek drive in my Amiga 500
https://www.thingiverse.com/thing:2745049 Summary From my original list of 25 things to print, I've done 7 of them and determined 4 are not viable. The things in this list I've printed have been off-the-shelf models that other people have constructed. The things I haven't printed are designs I will do myself, which is one reason I haven't printed them yet: building your own designs is the hard part!

9 September 2022

Jonathan Dowland: memtest

Since I'm writing about my NAS, a month ago I happened to notice an odd kernel message:
Aug 8 04:04] list_del corruption. prev->next should be ffff90c96e9c2090,
but was ffff90c94e9c2090
A kernel dev friend said "I'm familiar with that code ... you should run memtest86". This seemed like advice it would be foolish to ignore! I installed the memtest86 package, which on Debian stable, is actually the formerly open-source "memtest86" software, last updated in 2014, rather than the currently open-source "memtest86+". However the package (incorrectly, I think) Recommends: memtest86+ so I ended up with both. The package scripts integrate with GRUB, so both were added as boot options. Neither however, would boot on my NAS, which is a UEFI system: after selection from the GRUB prompt, I just had a blank screen. I focussed for a short while on display issues: I wondered if trying to run a 4k monitor over HDMI was too much to expect from a memory tester OS, but my mainboard has a VGA out as well. It has some quirky behaviour for the VGA out: the firmware doesn't use it at all, so output only begins appearing after something boots (GRUB for example). I fiddled about with the HDMI output, VGA output, and trying different RGB cables, to no avail. The issue was (likely) nothing to do with the video out, but rather that the packaged versions of memtest/memtest86+ don't work properly on UEFI systems. What did work, was Passmark Software's non-FOSS memtest86. It drew on HDMI, albeit in a postage stamp sized window. After some time (much less than I expected, some kind of magic modern memory matrix stuff going on I think), I got a clean bill of health:
memtest86(.com) passes
It's quite possible the FOSS versions of memtest (pcmemtest is another) have better support for UEFI in more recent versions than I installed (I just went with what's in Debian stable), and if not, then this is a worthy feature to work on.

6 September 2022

Jonathan Dowland: Borg corrupted hints file

I've been using Borg backup for a couple of years and it has seemingly worked very well for me. One difference I really appreciate from my previous arrangement (rdiff-backup) is the freedom to move large files or file hierarchies around (including between different filesystems) without provoking large backup incrementals. About a week ago I had my first real problem with Borg: backups started to fail with the following complaints:
Creating archive at "/backup/borg:: hostname -home-jon- now:%Y-%m-%dT%H:%M:%S.%f "
segment 61916 not found, but listed in compaction data
[ further, similar lines ]
Local Exception
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/borg/archiver.py", line 4690, in main
    exit_code = archiver.run(args)
  File "/usr/lib/python3/dist-packages/borg/archiver.py", line 4622, in run
    return set_ec(func(args))
  File "/usr/lib/python3/dist-packages/borg/archiver.py", line 177, in wrapper
    return method(self, args, repository=repository, **kwargs)
  File "/usr/lib/python3/dist-packages/borg/archiver.py", line 595, in do_create
    create_inner(archive, cache)
  File "/usr/lib/python3/dist-packages/borg/archiver.py", line 560, in create_inner
    archive.save(comment=args.comment, timestamp=args.timestamp)
  File "/usr/lib/python3/dist-packages/borg/archive.py", line 530, in save
    self.repository.commit()
  File "/usr/lib/python3/dist-packages/borg/repository.py", line 475, in commit
    self.compact_segments()
  File "/usr/lib/python3/dist-packages/borg/repository.py", line 835, in compact_segments
    assert segments[segment] == 0, 'Corrupted segment reference count - corrupted index or hints'
AssertionError: Corrupted segment reference count - corrupted index or hints
At about the same time I had managed to fill the backup host's root filesystem. I thought the two issues must be related. Although all the files Borg is backing up, and the backup repository it writes to, are located on different partitions, Borg's client-side of things does maintain some caching in /root/.cache/borg. My first idea was that this must have been corrupted by an aborted write, but zapping it did not cure the above problem. It occurred to me that I run Borg via the convenience wrapper Borgmatic, and it was possible that was failing, but after a short investigation I ruled that out. Various attempts at running borg check or borg check --repair didn't help either. The underlying filesystem (XFS) passed a filesystem check. There wasn't any obvious complaints about IO errors from the kernel or anything reported in the HDD's SMART data. What did work, in the end, was removing the file matching $BORG_REPO/*hint* and trying again. Although this is read/written to on the backup partition, it seems filling the root partition caused Borg (1.1.16-3) to corrupt that file. Everything seems fine following that. I have recently started trying to semi- automatically verify backups on a monthly basis, on a machine independent from the NAS; all the tests I have written so far passed.

30 August 2022

Jonathan Dowland: Venineth

My turntable is temporarily out of action so this post is in lieu of a crate digging update. Some time ago, I saw Matt Hoye raving about a little indie game called Venineth. I think he said it was the perfect little game to relax to. I don t regularly play games but I could sometimes do with some help relaxing. I was reminded about Venineth when I saw some buzz about Exo One, a similar-looking game, so I thought I d give Venineth a go.
picture of a vinyl record A scene near the start of Venineth
It s great fun: Relaxing, mildly challenging, and satisfying. It didn t run terribly well on my T470s but I ve since upgraded to a workstation which should handle it easily so I need to try it again. The reason this is a substitute for a crate digging post: although I ve not picked Venineth back up in a while, I have had the soundtrack on a reasonably heavy rotation. It s an immersive, synth driven instrumental album by polish musician Echo Ray that is good music to listen to when concentrating.

26 August 2022

Jonathan Dowland: Replacement nosecone for Janod Rocket

My youngest has a cute little wooden Rocket puzzle, made by a French company called Janod. Sadly, at some point, we lost the nose cone part, so I designed and printed a replacement.
Rocket cone
It's substantially based on one module from an OpenSCAD "Nose Cone Library" by Garrett Goss, which he kindly released to the public domain. I embellished the cone with a top pointy bit and a rounded brim. I also hollowed out the bottom to make space for a magnet. Originally I designed an offset-from-centre slot for the magnet, the idea being, you would insert the magnet off-centre and it would slot into position and be partly held in by the offset, and you could then stick a blob of glue or similar to finish the job. Unfortunately I had a layer shift during the print, so that didn't work. I reamed out a small alcove instead. The white trim is adapted from the lid from some kitchen herbs, trimmed back. I secured the magnet and glued the lid over the bottom. Here it is: rocket.scad. My contributions are under the terms of Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0).

25 August 2022

Jonathan Dowland: IKEA HEMNES Shoe cabinet repair

 1
 2
 3

Over time the screw hole into the wooden front section of our IKEA HEMNES Shoe cabinet had worn out and it was not possible to secure a screw at that position any more. I designed a little 'wedge' of plastic to sit over the fitting with and provide some offset screw holes. At the time, I had a very narrow window of access to our office 3d printer, so I designed it almost as a "speed coding" session in OpenSCAD: in between 5-10 minutes, guessing about the exact dimensions for the plastic bit that it sits over.

Jonathan Dowland: dues (or blues)

After I wrote hledger, I got some good feedback, both from a friend in-person and also on Twitter. My in-person friend asked, frankly, do I really try to manage money like this: tracking every single expense? Which affirms my suspicion, that many people don't, and that it perhaps isn't essential to do so. Combined with the details below, 3/4 of the way through my experiment with using hledger, I'm not convinced that it has been a good idea. I'm quoting my Twitter feedback here in order to respond. The context is handling when I have used the "wrong" card to pay for something: a card affiliated with my family expenses for something personal, or vice versa. With double-entry book-keeping, and one pair of transactions, the destination account can either record the expense category:
2022-08-20  coffee
    family:liabilities:creditcard     -3
    jon:expenses:coffee                3
or the fact it was paid for on the wrong card
2022-08-20  coffee
    family:liabilities:creditcard     -3
    family:liabilities:jon             3 ; jon owes family
but not easily both. https://twitter.com/pranesh/status/1516819846431789058:
When you accidentally use the family CV for personal expenses, credit the account "family:liabilities:creditcard:jon" instead of "family:liabilities:creditcard". That'll allow you to track w/ 2 postings.
This is an interesting idea: create a sub-account underneath the credit card, and I would have a separate balance representing the money I owed. Before:
$ hledger bal -t
              -3  family:liabilities:creditcard
               3  jon:expenses:coffee
transaction
2022-08-20  coffee
    family:liabilities:creditcard:jon     -3
    jon:expenses:coffee                    3
Corresponding balances
$ hledger bal -t
              -3  family:liabilities:creditcard
              -3    jon
               3  jon:expenses:coffee
Great. However, what process would clear the balance on that sub-account? In practice, I don't make a separate, explicit payment to the credit card from my personal accounts. It's paid off in full by direct debit from the family shared account. In practice, such dues are accumulated and settled with one off bank transfers, now and then. Since the sub-account is still part of the credit card heirarchy, I can't just use a set of virtual postings to consolidate that value with other liabilities, or cover it. Any transaction in there which did not correspond to a real transaction on the credit card would make the balance drift away from the real-word credit statements. The only way I could see this working would be if the direct debit that settles the credit card was artificially split to clear the sub-account, and then the amount owed would be lost. https://twitter.com/pranesh/status/1516819846431789058:
Else, add: family:assets:receivable:jon $3
jon:liabilities:family:cc $-3
A "receivable" account would function like the "dues" accounts I described in hledger (except "receivable" is an established account type in double-entry book-keeping). Here I think Pranesh is proposing using these two accounts in addition to the others on a posting. E.g.
2022-08-20  coffee
    family:liabilities:creditcard     -3
    jon:expenses:coffee                3
    family:assets:receivable:jon       3
    jon:liabilities:family            -3
This balances, and we end up with two other accounts, which are tracking the exact same thing. I only owe 3, but if you didn't know that the accounts were "views" onto the same thing, you could mistakenly think I owed 6. I can't see the advantage of this over just using a virtual, unbalanced posting. Dues, Liabilities I'd invented accounts called "dues" to track moneys owed. The more correct term for this in accounting parlance would be "accounts receivable", as in one of the examples above. I could instead be tracking moneys due; this is a classic liability. Liabilities have negative balances.
jon:liabilities:family    -3
This means, I owe the family 3. Liability accounts like that are identical to "dues" accounts. A positive balance in a Liability is a counter-intuitive way of describing moneys owed to me, rather than by me. And, reviewing a lot of the coding I did this year, I've got myself hopelessly confused with the signs, and made lots of errors. Crucially, double-entry has not protected me from making those mistakes: of course, I'm circumventing it by using unbalanced virtual postings in many cases (although I was not consistent in where I did this), but even if I used a pair of accounts as in the last example above, I could still screw it up.

24 August 2022

Jonathan Dowland: Our Study, 2022

Two years ago I blogged a photo of my study. I'd been planning to revisit that for a while but I'd been somewhat embarrassed by the state of it, but I've finally decided to bite the bullet.
Fisheye shot of my home office, 2022 Fisheye shot of my home office, 2022
What's changed The supposedly-temporary 4x4 KALLAX has become a permanent feature. I managed to wedge it on the right-hand side far wall, next to the bookcase. They fit snugly together. Since I'd put my turntable on top, I've now dedicated the top row of four spaces to 12" records. (There's a close-up pic here). My hi-fi speakers used to be in odd places: they're now on my desktop. Also on my desktop: a camera, repurposed as a webcam, and a 90s old Creative Labs beige microphone; both to support video conferencing. The desktop is otherwise, largely unchanged. My Amiga 500 and Synthesiser had continued to live there until very recently when I had an accident with a pot of tea. I'm in two minds as to whether I'll bring them back: having the desk clear is quite nice. There's a lot of transient stuff and rubbish to sort out: the bookcase visible on the left, the big one behind my chair on the right (itself to get rid of); and the collection of stuff on the floor. Sadly, the study is the only room in our house where things like this can be collected prior to disposal: it's disruptive, but less so than if we stuffed them in a bedroom. You can't easily see the "temporary" storage unit for Printer(s) that used to be between bookcases on the right-hand wall. It's still there, situated behind my desk chair. I did finally get rid of the deprecated printer (and I plan to change the HP laser too, although that's a longer story). The NAS, I have recently moved to the bottom-right Kallax cube, and that seems to work well. There's really no other space in the Study for the printer. Also not pictured: a much improved ceiling light. What would I like to improve First and foremost, get rid of all the transient stuff! It's a simple matter of not putting the time in to sort it out If I manage that, I've been trying to think about how to best organise material relating to ongoing projects. Some time ago I salivated over this home office tour for an embedded developer. Jay has an interesting project tray system. I'm thinking of developing something like that, with trays or boxes I can store in the Kallax to my right. I'd love to put a comfortable reading chair, perhaps a wing-backed thing, and a reading light, over on the left-hand side near the window. And/or, a bench at a height enabling me to do the occasional bit of standing work, and/or to support the Alesis Micron (or a small digital Piano).

15 August 2022

Jonathan Dowland: Temperature monitoring

Xiaomi Mijia Temperature Sensor Xiaomi Mijia Temperature Sensor
I've been having some temperature problems in my house, so I wanted to set up some thermometers which I could read from a computer, and look at trends. I bought a pack of three cheap Xiaomi IoT thermometers. There's some official Xiaomi tooling to access them from smartphones and suchlike, but I wanted something more open. The thermometers have some rudimentary security on them to try and ensure you use the official tooling. This is pretty weak, and the open-source Home Assistant (HA) has support for querying them. I wasn't already running HA and it looked to do more than I needed right now. gathering A friend told me that it was trivial to write custom firmware to the devices. It's so easy you can do it from a web-based flasher: in fact, anyone in range can. There's a family of custom firmwares out there, and most move the sensors readings into the BTLE announce packets, meaning, you can scrape the temperature by simply reading and decoding the announcement packets, no need to handshake at all, and certainly no need to navigate Xiaomi's weird security. This is the one I used. I hacked up a Python script to read the values with the help of this convenience library1. Next, I needed to set up somewhere to write the values. reporting
The study is thankfully cooler today The study is thankfully cooler today
It's been long enough since I last looked at something like this that the best in class software was things like multi router traffic grapher, and rrdtool, or things that build on top of them like Munin. The world seems to have moved on (rightly or wrongly) with a cornucopia of options like Prometheus, Grafana, Graphite/Carbon, InfluxDB, statsd, etc. I ruled most of these out as being too complex for what I want to do, and got something working with Graphite (front-end) and Carbon (back-end). I was surprised that this wasn't packaged in Debian, and opted to try the Docker container. This works, although even that is more complex than I need: it's got graphite and carbon, but also nginx and statsd too; I'm submitting directly to carbon, side-stepping statsd entirely. So as I refine what I'm doing I might possibly strip that back. next steps I might add more sensors in my house! My scripts also need a lot of tidying up. But, I think it would be useful to add some external temperature data, such as something from a Weather service. I am also considering pulling in some of the sensor data from the Newcastle University Urban Observatory, which is something I looked at a while ago for my PhD but didn't ultimately end up using. There are several temperature sensors nearby, but they seem to operate relatively sporadically. There's a load of other interesting sensors in my vicinity, such as air quality monitors. I'm currently ignoring the humidity data from the sensors but I should collect that too. It would be useful to mark relevant "events", too: does switching on or off my desktop PC, or printer, etc. correlate to a jump in temperature?

  1. I might get rid of that in the future as I refine my approach

7 July 2022

Jonathan Dowland: Musick To Play In The Dark 2

This took a while to arrive! After the success of the reissue of Coil's Musick To Play In The Dark, it was inevitable that the second edition would also be reissued. The pre-order opened late November 2021 and mine arrived in late April this year.
Record cover
I was toying with the idea of ordering one of the most exclusive editions direct from DAIS Records, in particular the glow in the dark one, but with international shipping the cost was pretty high. I went with a UK distributor (Boomkat) instead, who had their own exclusive edition: black-in-purple-in-clear.
records
I'm happy with my decision: it's one of the most interesting variants I own, and from what I've read, glow in the dark vinyl never sounds great anyway. (I think I have at least one glow in the dark 7" single somewhere) Stand-out track: Tiny Golden Books Since I didn't say so last time, the stand-out track on volume one is Red Birds Will Fly Out of the East and Destroy Paris in a Night, but both volumes are full of really interesting moments ( One day, your eggs are going to hatch and some very strange birds are going to emerge. )

28 June 2022

Jonathan Dowland: WadC 3.1

Example map with tuneables on the right Example map with tuneables on the right
WadC the procedural programming environment for generating Doom maps version 3.1 has been released. The majority of this was done a long time ago, but I've dragged my feet in releasing it. I've said this before, but this is intended to be the last release I do of WadC. The headline feature for this release is the introduction of a tuning concept I had for the UI. It occurred to me that a beginner to WadC might want to load up an example program which is potentially very complex and hard to unpick to figure out how it works. If the author could mark certain variables as "tuneable", the UI could provide an easy way for someone to tweak parameters and then see what happened. I had in mind the walls of patch panels and knobs you see with analog synthesizers: tweak this thing over here and see what happens over there. I think this kind of feature would be useful in other, similar programming environments, like OpenSCAD: I don't think they do yet, but I could be wrong.
Kayvan and Me, riding horse statues, somewhere in Germany, in the 1990s
This release of WadC is dedicated to the memory of Kayvan Walker (1983-2022). Kayvan was a childhood friend who committed suicide in March this year. Back in the nineties, Kayvan was responsible for introducing me to Doom in the first place: I used to visit his house on the way home to mine, as it was on the walk back from School. His mum works in IT and always encouraged us into it. Doom was so far ahead, in technical terms, of any other computer game I'd ever seen, and was the closest thing we had to virtual reality: we could create our own worlds. It's in no small part thanks to Kayvan and his Mum that I'm still creating worlds, nearly thirty years later. I owe my career and most of my hobbies to those pivotal moments. Thank you both. Kayvan did a lot more for me than just introduce me to Doom, or computing. He was one of a set of friends that I had every confidence that, no matter what, we would always be friends, through thick and thin. I miss him terribly. Please, if you reading this, are suffering, talk to someone. In the UK you can talk to Samaritans on 116 123.

9 June 2022

Jonathan Dowland: Fight Club OST

the record packaging
I often listen to soundtracks when I'm concentrating. The Fight Club soundtrack, by the Dust Brothers, is not one I turn to very often. I do love the way it was packaged for vinyl. The cover design references IKEA, but the clever thing is it has a mailer-style pull-cord to open it up. You can't open the packaging using it without literally tearing the package in half. There is a secret, alternative way to get in with less damage, but if you try it the packaging has a surprise for you. This Image album summarizes most of the packaging secrets. The records themselves are a pleasant mottled pink colour, reminiscent of the soap bars in the movie. They're labelled "Paper Street Soap Company".
close up of the pink record

12 May 2022

Jonathan Dowland: Scalable Computing seminar

title slide
Last week I delivered a seminar for the research group I belong to, Scalable Computing. This was a slightly-expanded version of the presentation I gave at uksystems21. The most substantial change is the addition of a fourth example to describe recent work on optimising for a second non-functional requirement: Bandwidth.

29 April 2022

Jonathan Dowland: hyperlinked PDF planner

The Year page The Year page
A day page A day page
I've been having reasonable success with time blocking, a technique I learned from Cal Newport's writings, in particular Deep Work. I'd been doing it on paper for a while, but I wanted to try and move to a digital solution. There's a cottage industry of people making (and selling) various types of diary and planner as PDF files for use on tablets such as the Remarkable. Some of these use PDF hyperlinks to greatly improve navigating around. This one from Clou Media is particularly good, but I found that I wanted something slightly different from what I could find out there, so I decided to build my own. I explored a couple of different approaches for how to do this. One was Latex, and here's one example of a latex-based planner, but I decided against as I spend too much time wrestling with it for my PhD work already. Another approach might have been Pandoc, but as far as I could tell its PDF pipeline went via Latex, so I thought I might as well cut out the middleman. Eventually I stumbled across tools to build PDFs from HTML, via "CSS Paged Media". This appealed, because I've done plenty of HTML generation. print-css.rocks is a fantastic resource to explore the print-specific CSS features. Weasyprint is a fantastic open source tool to convert appropriately-written HTML/CSS into PDF. Finally I wanted to use a templating system to take shortcuts on writing HTML. I settled for embedded Ruby, which is something I haven't touched in over a decade. This was a relatively simple project and I found it surprisingly fun. The results are available on GitHub: https://github.com/jmtd/planner. Right now, you get exactly what I have described. But my next plan is to add support for re-generating a planner, incorporating new information: pulling diary info from iCal, and any annotations made (such as with the Remarkable tablet) on top of the last generation and preserving them on the next.

22 April 2022

Jonathan Dowland: 3D-printed replacement battery cover

Print next to the original Print next to the original
new cover in the light new cover in the light
My first self-designed functional 3D print is a replacement battery cover for a LED fake-candle that my daughter uses as a night-light. I measured the original cover (we have three of the candles) using a newly-purchased micrometer and tried to re-create it in OpenSCAD. I skipped the screw-hole that is for securing the cover as we don't use that. I sliced it using Cura and printed it using PETG on our office 3D printer, a Ender 3. Print time was about an hour. To my amazement, my first take fits snugly! I've uploaded the OpenSCAD source here: batterycover.scad. It's covered under the terms of Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0).

14 April 2022

Jonathan Dowland: hledger

This year I've decided to bite the bullet and properly try out hledger for personal accounting. It seems I need to commit to it properly if I'm to figure out whether it will work for me or not. Up until now I'd been strictly separating my finances into two buckets: family and personal. I'd been using GNUCash for a couple of years for my personal finances, initially to evaluate it for use for the family, but I had not managed to adopt it for that. I set up a new git repository to track the ledger file, as well as a notes.txt "diary" that documents my planning around its structure and how to use it, and a import.txt which documents what account data I have imported and confirmed that the resulting balances match those reported on monthly statements. For this evaluation, I decided to bite the bullet and track both family and personal finances at the same time. I'm still keeping them conceptually very separate. To reflect that I've organised my account names around that: all accounts relating to family are prefixed family:, and likewise personal jon:.1 Some example accounts:
family:assets:shared    - shared bank account
family:dues:jon         - I owe to family
family:expenses:cat     - budget category for the cat
income                  - where money enters this universe
jon:assets:current      - my personal account
jon:dues:peter          - money Peter owes me
jon:expenses:snacks     - budget category for coffees etc
jon:liabilities:amex    - a personal credit card
I decided to make the calendar year a strict cut-over point: my personal opening balances in hledger are determined by what GNUCash reports. It's possible those will change over this year, as adjustments are made to last year's data: but it's easy enough to go in and update the opening balances in hledger to reflect that. Credit cards are a small exception. January's credit card bills are paid in January but cover transactions from mid-December. I import those transactions into hledger to balance the credit card payment. As a consequence, the "spend per month" view of my data is a bit skewed: All the transactions in December should be thought of as in January since that's when they were paid. I need to explore options to fix this. When I had family and personal managed separately, occasionally something would be paid for on the wrong card and end up in the wrong data. The solution I used last year was to keep an account dues:family to which I posted those and periodically I'd settle it with a real-world bank transfer. I've realised that this doesn't work so well when I manage both together: I can't track both dues and expense categorisation with just one posting. The solution I'm using for now is hledger's unbalanced virtual postings: a third posting for the transaction to the budget category, which is not balanced, e.g.:
2022-01-02 ZTL*RELISH
    family:liabilities:creditcard        -3.00
    family:dues:jon                       3.00
    (jon:expenses:snacks)                 3.00
This works, but it completely side-steps double-entry book keeping, which is the whole point of using a double-entry system. There's also no check and balance that the figure I put in the virtual posting ( 3) matches the figure in the rest of the transaction. I'm therefore open to other ideas.

  1. there are a couple of places in hledger where default account names are used, such as the default place that expenses are posted to during CSV imports: expenses:unknown, that obviously don't fit my family/jon: prefix scheme. The solution is to make sure I specify a default posting-to account in all my CSV import rules.

13 April 2022

Jonathan Dowland: Another Green World

Brian Eno's classic 1975 album Another Green World, with the iconic cover crop from Tom Philip's After Raphael. This is a recent pressing. I try to avoid buying new vinyl, and I think I got this as part of a trade-in swap two years ago when I went to get one of my first Covid vaccinations in Newcastle. It was the first time I'd been anywhere near a record shop (which was adjacent to the temporary vaccine centre) in a year or more, and I took the opportunity to bring in some records to sell. I definitely left with fewer records than I went in with, at least
Another Green World on the turntable
What to say about this album? It's a classic, it's weirdly compelling, it dances over the line between engaging your attention and something you can have on in the background. Many of the tracks are quite short relative to the ideas they express: I imagine some remixer could have a lot of fun with it. The Big Ship is perhaps the standout, but I really like the title track, and opener Sky Saw too. It's probably the first album written using using the oblique strategies card system.
Card reading 'You are an Engineer'

11 April 2022

Jonathan Dowland: With Teeth

Sometimes people ask me which is the best entry point for Nine Inch Nails, and I have trouble answering. I've eventually decided that it's 2005's With Teeth.
Picture of 'With Teeth' playing on my turntable
I've pulled this from my pile of records to sell. Most Nine Inch Nails stuff seems to increase in value over time, and it's got to the stage that some of the ones in my collection are now valuable enough that I'm nervous to play them, which makes them a little pointless. A couple of years ago, a handful of the albums were re-issued (including With Teeth, here, and The Fragile, which hadn't been repressed since 1999). I had a vague plan to sell off my original pressings to someone who would appreciate them more and use the takings to buy the re-issues, but I didn't move fast enough, and now the re-issues are (for the most part) also sought-after.

6 April 2022

Jonathan Dowland: Hope in a Darkened Heart

I first heard Virginia Astley via Lauren Laverne, who played (I think) "With my eyes wide open" from her first album, "From Gardens Where We Feel Secure". Mostly ambient, a conceptual piece about a garden in an English Summer, spanning dawn to dusk. Bucolic ambient, dream pop. It was a little outside my wheel-house, but I loved it, and wanted to find out more. I soon learned that official, physical copies of it were rare and expensive.
'Hope in a Darkened Heart' spinning on my turntable
Some time later I stumbled across her second album "Hope in a Darkened Heart" (which is possibly the most commonly available of her albums) and bought it blind. It's quite different, with a lot more singing, but whatever drew me to Gardens is present. I love this. It was produced by Ryuichi Sakamoto. Only this week I was enormously pleased to discover a chunk of her discography on Bandcamp, including the two aformentioned albums. Highlights from Darkened:

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