Linux Fu: Fake Webcams Have Many Uses

May 28, 2026 by Al Williams 14 Comments

Dealing with text streams is a fundamental skill for the Linux power user. You can sort, merge, and search text files easily from the command line. What if you could do the same thing with video? Well, you can. Maybe you want to add a logo to a webcam feed before sending it to a conference app. Maybe you want to blur, color-correct, or annotate video in real time. Or perhaps you want to inject prerecorded video into Zoom while pretending it is a live camera. Linux can do all of this, and the key ingredient is usually the same: a loopback video device.

The basic idea is simple. Instead of an application reading directly from /dev/video0, you create a fake camera device using the v4l2loopback kernel module. Your software pipeline writes processed video into the fake camera, and applications read from it as if it were a normal webcam. The result is surprisingly powerful.

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Virtual Museum Hosts Every OS You Haven’t Heard Of

May 28, 2026 by Tyler August 11 Comments

OK, every operating system is a bit of a stretch — Windows Vista notably didn’t make the cut — but [Andrew]’s Virtual OS museum has a good claim to being the most comprehensive archive of operating systems yet assembled.

[Andrew] has a blog post describing the project, as well as a YouTube video that we’ve embedded below. But the real fun is in the downloading and spinning up one of 570+ operating systems for more than 250 platforms on pre-configured virtual machines that have been packaged up for us.

This isn’t just the usual retrocomputer nostalgia-fest of Macintosh System and DOSBox. There’s everything from IBM Big Iron and VAXen to Texas Instrument graphing calculators emulated in the museum, with software to run on them, too. If you’ve ever wondered what you could do with the Manchester Baby, well, all known software for that machine is included with its ‘operating system’.

Admission is free, but like any good museum you’ll be waiting in line a while to get in, so expect the full 128 GB download to take some time. If you’re into computer history, though, it’s going to very much be worth the wait. If you try it and like it, you could help others by seeding the torrent.

The actual museum launches in a VM as a modern Linux system — perhaps that can be considered an exhibit itself — with a launcher to select any of the other system/OS combos, including various other, older Linuxes hosted on their own VMs. There are more to come, too, as [Andrew] continues the long debugging process of making sure everything works as expected.

Purists may decry this virtual emulation as not being quite the real thing, which is true. But while MiSTer supports a lot of cores via FPGA, you probably won’t find everything here on that platform. We have, however, seen an FPGA recreation of the Manchester Baby. More than once, even.

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Testing LFP Battery Failure Modes With Overcharging

May 28, 2026 by Maya Posch 31 Comments

As great as batteries are, it’s essential to understand their risks and how to keep them from going spicy. Recently there has been a bit of a fuss about the dangers of LiFePO₄ (LFP) batteries after someone’s dedicated LFP battery shed got shredded into matchsticks by a hydrogen explosion, following said LFP batteries having a thermal event. The thing about the LFP chemistry is that if it suffers such a thermal event, it generates hydrogen gas, which is one of the most explosion-happy gases known to man. This is demonstrated in a recent video by [Will Prowse].

To kick things off, a single prismatic LFP cell is overcharged for half an hour after it was already at 100% state of charge. This ultimately pops the vent as the cell begins to release hydrogen gas into the aquarium that the cell was placed in. Using a spark generator it’s then attempted to ignite the gas, which initially takes a bit as enough hydrogen has to collect first.

Once there’s ignition, however, it happily keeps burning as more and more hydrogen pours out of the by now bulging cell’s vent. If any other LFP cells had been nearby these too would be at risk of suffering thermal runaway, showing how just one bad LFP cell is enough to potentially set an LFP battery bank ablaze.

In a commercial setting you will have precautions such as hydrogen sensors, ventilation and spark generators to deal with any generated hydrogen gas, as well as blow-out panels in case things end up going squirrely in a hurry.

While a benefit of LFP chemistry is that it does not generate its own oxygen as with other lithium-ion chemistries, hydrogen gas is a major problem due to how incredibly volatile it is. It’s not just a headache with battery storage, but also in the nuclear power sector, where zirconium fuel rod cladding can very efficiently turn steam into hydrogen and oxygen. This was the reason why some of Fukushima Daiichi’s buildings suffered detonations, with the nuclear plant operator opting to not install recommended hydrogen gas mitigation systems.

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Decoding The Tianwen-2 Sample Return Mission’s Telemetry Signal

May 27, 2026 by Maya Posch No comments

China’s Tianwen-2 asteroid sample return mission launched on 28 May of 2025 and is scheduled to arrive at its target – near-Earth asteroid 469219 Kamo’oalewa – in June 2026. This gives folk back on Earth plenty of time to listen in on the probe’s communication with its home base, such as [Daniel Estévez] who recently had a poke at this telemetry as captured by the Dwingeloo radio telescope in the Netherlands.

With not a lot of public information on its trajectory it’s a hard probe to track, but now that it’s nearing its destination there’s an obvious part of the sky to aim for. This is X-band telemetry, broadcast at 8428.19 MHz, with the same basic modulation as its predecessor Tianwen-1.

Where it differs is in the coding, with Tianwen-2 also using concatenated coding, but having a frame length that’s better suited to submitting full Reed-Solomon codewords and does not require omitting bytes to make things awkwardly fit.

After analyzing the telemetry data itself, there doesn’t seem to be anything exciting contained within this capture. This does seem to be as expected considering that the probe is still in its coast phase where it doesn’t have to do much and likely is in a low-power state most of the time. Once its orbital insertion burn begins is when this knowledge can likely be used to track the mission in fine-grained detail, which is an event that we’re definitely looking forward to.

Linux Distributions And Who Is Responsible For The Software

May 27, 2026 by Maya Posch 56 Comments

The topic of downstream and upstream is an important one in the Linux ecosystem, where from one base distribution you can go many layers of distros deep before even looking at all the other base distributions. Within that veritable jungle you get questions about who is responsible for packaging software, where to report bugs found with a specific application, as well as what ‘LTS’ truly means in a consumer context. These and other points are raised in a recent video by [Brodie Robertson], with many examples of things going tragically wrong.

There’s a good argument to be made that ultimately it is the distro that is responsible for the software that they provide via their repositories. As [Brodie] shows in the video, there are a few cases where an ‘LTS’ distro uses an old version of some software that contains a bug that has been fixed a while ago, so reporting it to the developer is rather pointless, while the distro maintainers should fix it with backporting of patches or updating the version.

From an end user experience this also makes the most sense, as in the end they just want to have the Windows experience of downloading a proverbial installer, clicking through whatever dialogs pop and have working software. If the software is provided via the distro, it is their responsibility, the same way that you contact the developer if you get a DEB or RPM from a GitHub project page and it doesn’t work.

This current Linux Chaos Vortex can be called a major issue when e.g. FreeBSD has no such upstream/downstream issues, with cross-platform installers being basically impossible on Linux ever since the Linux Standard Base effort died.

Perhaps Linux will get a distroless future, however, which may finally herald that Year of the Linux Desktop.

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Autopsy Of A Failed Vintage Carbon Resistor

May 27, 2026 by Maya Posch 5 Comments

Detail of the lead connecting to the inner carbon-filled tube. (Credit: CuriousMarc)

Although resistors are hardly among the most exciting components, they are arguably one of the most important ones, as anyone who has done any amount of circuit design and debugging can attest to. So too with a single carbon resistor in a vintage Metrix oscilloscope that [CuriousMarc] recently repaired. After recapping the board there was still a major issue that got traced down to said resistor. After replacing it with a fresh resistor obviously this meant doing an autopsy to see why the old resistor had failed.

The 20 kOhm-rated resistor looked fine on the outside, with no obvious damage or discoloration, but it measured around 0.843 MOhm. To get to the insides [CuriousMarc] asked his friend [TubeTime] on how to proceed. The answer here was sandpaper and a lot of patience, and thus the experiment to see how much sanding it takes to get to the core of a fairly big resistor commenced.

Ultimately the insides were revealed, and they turned out to be rather interesting, with what looked like a glass tube filled with what would be the carbon-laden material between the two lead terminals. From poking around a bit at these insides it would appear that the failure mode was a degraded contact between these terminals and the carbon material. Considering that this resistor is many decades old and has gone through many thermal cycles and potentially various kinetic events some fractures are probably to be expected.

Perhaps most fascinating is the construction of this carbon resistor that looks to be a step above that of the average carbon resistor that [TubeTime] has taken apart over the years.

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A black-and-white clock face is shown. The numerals are ranged around the right edge of the clock. One pointer extends from the center of the clock, and one is on the left side of the face.

A Clock Inspired By Failed Cognitive Tests

May 27, 2026 by Aaron Beckendorf 81 Comments

One simple screening tool for cognitive impairment is the clock-drawing test (CDT): the patient is provided with a printed circle and asked to draw a clock face with the hands pointing to a certain time. Depending on how the clock is drawn, this could indicate a variety of different disorders, particularly dementia, with a particular deformity in the drawing sometimes pointing to a specific issue. These failed tests inspired [John Silvia] to create a clock with a unique, disordered face.

The numerals in this clock face are placed exclusively along the right half of the clock (in the test, this can be a sign of damage to the right parietal lobe, or of executive dysfunction caused by dementia), and out of order. The hour hand is controlled by a servo motor, and the minute hand is mounted on a separate, commercially-purchased clock mechanism on the left-hand side of the face.

The frame for the clock and the face are 3D-printed, and the servo motor is controlled by an ESP32-C3 with an RTC module. To minimize power draw, a MOSFET disconnects the servo motor from power except for the once-per-hour position update. Once per month, the ESP32 connects to Wi-Fi to synchronize to NTP time, otherwise remaining in a low-power state – even its indicator LEDs are disconnected to save power. These efforts paid off: when the servo isn’t active, it draws only about 160 µA, and a set of three AA NiMH cells lasts about a year.

Since the servo motor draws most of the power budget, it wouldn’t make much difference, but the ESP32’s co-processor can also be used for ultra-low-power projects. For a happier take on a drawing-related clock, check out one of these projects.