this post was submitted on 26 Sep 2026

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submitted 3 days ago* (last edited 2 days ago) by A_norny_mousse@piefed.zip to c/linux@lemmy.ml

37 comments fedilink hide all child comments

final edit: You want real logs instead? add this to your kernel command: drm.panic_screen=kmsg

Kinda funny, kinda neat.

I have no idea what the QR-code might reveal (I could not read it from this picture), so I pixelised it just to be sure.

FWIW I know exactly what happened and did not panic. To reproduce, boot your device with init=/bin/sh, then type exit.

CachyOS

The picture above is generated by Drm panic which is part of the kernel itself, or maybe a separate module. The data in the QR code is the kmsg log.

Not systemd, which wasn't running when that happened.

And it's been around for years; I guess I haven't had a kernel panic in a long time.

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[–] mactan@lemmy.ml 1 point 1 day ago*

when your boot doesn't get far enough to use termbin this is the next next best thing . remember, nobody wants a smartphone picture of a monitor with logs on it

[–] black0ut@pawb.social 23 points 3 days ago* (15 children)

The QR code contains the panic stack trace text, directly encoded into a URL and a parameter. When you scan it, it goes to the website, which takes the parameter, decodes it and displays it as plain text.

Personally, I think it's a terrible idea compared to just showing the logs, because now you need internet and a phone with a camera to read a kernel panic log.

Edit: yes, it was Systemd who implemented it.

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[–] SteveTech@aussie.zone 22 points 3 days ago (1 child)

Edit: yes, it was Systemd who implemented it.

Nah, systemd-bsod is different and designed to show info about boot failures:

systemd-boot screenshot

It's rather quite useless.

drm_panic on the other hand has nothing to do with systemd, and is what's shown in OPs post. The link can be quite useful for users to post their issues on bug reports or whatever. But if you know what you're doing, then it's pretty easy to configure it to print text instead.

Also remember, the reason drm_panic exists is because graphical outputs would otherwise freeze during a kernel panic, and not show anything useful.

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[+] A_norny_mousse@piefed.zip [S] 1 point 3 days ago

[deleted]

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[–] pipe01@programming.dev 4 points 2 days ago

It's a kernel thing, not systemd

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[–] A_norny_mousse@piefed.zip [S] 10 points 3 days ago* (last edited 3 days ago)

Thanks for the info, but this is not that.

The picture above is generated by Drm panic which is part of the kernel itself, or maybe a separate module. The data in the QR code is the kmsg log.

Not systemd, which makes sense considering systemd was not running when that happened.

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[–] signofzeta@lemmygrad.ml 4 points 3 days ago (2 children)

That QR code could be helpful, but why can’t we have both? Show me the backtrace and logs, and stick a code in the corner in case I need the Internet’s help.

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[–] 4am@lemmy.zip 3 points 2 days ago (1 child)

The QR stacktrace allows a method of copying the information off the machine, which may now be unable to function any longer.

If this error meant you can no longer boot to retrieve the error it’s goin to take you a lot longer to fix it because you have to now find the problem with no clues.

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[–] signofzeta@lemmygrad.ml 1 point 2 days ago

I get it. It’s more descriptive than an error message, and the few kilobytes you can cram into a QR code is great for that.

It sounded like other people were worried about data exfiltration, or disclosure to a third party. I haven’t had a chance to test this. Where does the QR code go?

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[–] LeLachs@lemmy.ml 3 points 2 days ago

I disagree. The logs typically do not fit on the screen in text form, especially on low resolutions (like if the system has to fall back on an alternative graphics mode, which tends to happen more frequently in the event of a crash). Granted, a website is not the best possible solution and has the risk of leaking data but at least it is "a" solution. The data is encoded sure, but not in an obfuscated way. If you wanted, you could decode it with other means (for example a dedicated app that scans it).

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[–] eleijeep@piefed.social 4 points 3 days ago (6 children)

So it's leaking information about your system to an external site?

That's just what we need.

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[–] black0ut@pawb.social 4 points 3 days ago (4 children)

The theory is that the site just hosts a small JS snippet that locally decodes and shows you your logs.

But yeah, now that you mention it, it would be trivial for the site to get and store the logs, and you wouldn't even notice.

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[–] eleijeep@piefed.social 3 points 3 days ago* (3 children)

Oh I see. If the URL puts the sensitive information after the anchor, like https://example.com/bsod#sensitive-info-goes-here then the browser would never send that part to the server. Everything after the anchor is just used locally by the browser to scroll the page to a specific place (or in this case for the javascript to read and process).

You'd need to check every time you scan a QR code though that the # is in the URL and it's not malformed. Trivially replacing the # with a ? would turn the private URL into one that sends all the data in the GET request. It's training users to do something risky.

Oh and it also assumes that the javascript hasn't been tampered with to upload the data somewhere.

I don't like it.

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[–] A_norny_mousse@piefed.zip [S] 4 points 3 days ago (2 children)

It's possible to use QR code reader apps that do not automatically go to the WWW.

But who's going to go to that effort on their slab of glass?

I agree that the whole concept of QR code scanning is problematic.

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[–] LeLachs@lemmy.ml 3 points 2 days ago (1 child)

But who's going to go to that effort on their slab of glass?

Those who would like to make extra sure their data stays private. On an unrelated note, what kinds of data could be considered confidential in said log?

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[–] A_norny_mousse@piefed.zip [S] 2 points 2 days ago

Those who would like to make extra sure their data stays private.

Yes, well, exactly. You know not every question is a literal question, right?

what kinds of data could be considered confidential in said log?

I was wondering that myself. It's "the kmsg log", something to do with kernel mode switching or "graphics". My guess: the log itself is not problematic, but there might be some metadata added. Or then one creates that metadata by submitting the QR code.

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[–] A_norny_mousse@piefed.zip [S] 1 point 3 days ago* (last edited 3 days ago)

it’s leaking information

No.

Scanning the QR code (on a different device presumably) might do that though.
It's kinda what QR codes do.

But I agree, it's not a good idea. Because people will scan that code and let their slabs of glass do their thing.

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[–] Dirk@lemmy.ml 6 points 3 days ago* (7 children)

Okay, great. I don’t have a smartphone. So I cannot see the error log anymore.

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[–] LeLachs@lemmy.ml 3 points 2 days ago

The most important info is at the bottom of the screen. I also believe you can turn this feature off if you prefer plain text

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[–] mio@lemmy.mio19.uk 4 points 3 days ago

let's submit a patch to display error log as text too on the bluescreen

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[–] HelloRoot@lemy.lol 2 points 3 days ago*

Hey, I happened to have a handful of smartphones that still have an ok battery and just collect dust in the shelf.

If you want me to ship one to you, pm your address.

Gonna help my linux buddies so that they can scan QR codes if their OS crashes.

(not sarcasm)

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[–] A_norny_mousse@piefed.zip [S] 1 point 3 days ago (2 children)

I should've tried to switch ttys, might have helped.

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[–] SteveTech@aussie.zone 2 points 2 days ago* (1 child)

Switching ttys wouldn't have done anything. The kernel logs are usually saved to efi_pstore (or sometimes erst) by default though.

Edit: you can also set drm.panic_screen=kmsg as a kernel parameter to print the logs instead of the QR.

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[–] A_norny_mousse@piefed.zip [S] 1 point 2 days ago

👍

Drm panic provides different panic screens. The default is "user" which will display a simple friendly message telling the user to reboot the computer. But for kernel developers, you can also set it to "kmsg", to see the last kmsg lines (so this is equivalent to the current fbcon). You can select the panic screen in Kconfig, or as a module parameter (drm.panic_screen=user) or at runtime with "echo -n kmsg > /sys/module/drm/parameters/panic_screen"

In other words, cat /sys/module/drm/parameters/panic_screen will show you what the current status is.

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[–] mio@lemmy.mio19.uk 1 point 3 days ago

let’s submit a patch to display error log as text too on the bluescreen

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[–] ark3@lemmy.dbzer0.com 4 points 3 days ago (2 children)

https://github.com/systemd/systemd/issues/38098

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[–] aary@lemmy.ml 2 points 3 days ago

Nice dual display setup :)

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[–] A_norny_mousse@piefed.zip [S] 1 point 3 days ago* (last edited 2 days ago)

My picture looks like that (on one monitor of course) and it wasn't created by systemd, which wasn't even running when that happened, but by the drm_panic kernel module. I've edited the OP.

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[–] hexagonwin@lemmy.today 2 points 2 days ago (1 child)

can that dense code be scanned with a phone? pretty sure mine can't

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[–] A_norny_mousse@piefed.zip [S] 1 point 2 days ago

That's what happened to me too, although i tried to scan it later off the image I took.

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[–] Ephera@lemmy.ml 1 point 3 days ago* (last edited 2 days ago) (1 child)

Did you maybe try to press Esc?
When it shows the pretty boot logo, you can do that to see the logs, so maybe it works here as well...

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[–] SteveTech@aussie.zone 4 points 2 days ago

Nah, when a kernel panic hits then everything's screwed.

Pressing ESC does work for systemd-bsod (which is different) and as you mentioned Plymouth; but not drm_panic.

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[–] Sanguine@lemmy.dbzer0.com 1 point 3 days ago

I never scan, just check the journal for errors from previous boot after restart. Most recent was my pcie low power shenanigans with my onboard WiFi. Simple fix and now its working /no bsod since.

[+] dgriffith@aussie.zone -10 points 3 days ago* (last edited 2 days ago) (4 children)

"This just in - running commands that induce a kernel panic causes a kernel panic, we'll have more at 11."

The QR code is pretty dense , probably plenty of space to include the panic reason and stack trace.

Edit: For those of you that don't know, exiting or crashing the init process (PID 1) causes the kernel to panic. Essentially it's the, "Well what the hell do I do now if I have no processes to serve?" response.

Still, a QR code is a marked improvement on the "Something went wrong :(" message of recent Windows releases.

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[–] A_norny_mousse@piefed.zip [S] 8 points 3 days ago* (3 children)

“This just in - running commands that induce a kernel panic causes a kernel panic, we’ll have more at 11.”

What's with the snark? I'm just sharing what is funny (to me): that somebody gave a Linux kernel panic this aesthetic, referencing a familiar "feature" of a less loved OS.

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[–] HelloRoot@lemy.lol 6 points 3 days ago* (last edited 3 days ago) (2 children)

On lemmy you'll allways find the weirdos and elitists that have been pushed out of the mainstream.

The linux equivalent of bsod has been introduced pretty recently, so it's normal for few people to have experienced it yet.

Also somewhat relevant xkcd: https://xkcd.com/1053/

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[–] A_norny_mousse@piefed.zip [S] 2 points 3 days ago (1 child)

I get what you mean but this is not fediverse-specific.

I have meanwhile found out that the screen above was not produced by systemd but rather by the drm_panic kernel module. Makes sense since systemd wasn't running when it happened.

Next time it happens (hopefully not) I'll try to switch ttys, maybe the logs are still visible, white on black.

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[–] HelloRoot@lemy.lol 3 points 2 days ago*

It's a subculture phenomenon, and lemmy linux is a subculture of a subculture, so it's more intense.

I've been a moderator on some linux reddits in the past. And the less users there were in the sub, the more negativity, rudeness, gatekeeping and other toxicity was there. But ofc what I say is just an opinion based on my subjective experience so idk.

The linux kernel bsod is even younger than that, august 2024 iirc.

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