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Asking a question that's been bugging me on/off for a while. I have noted the above symbols (^@ and ū, sometimes only one of the two, sometimes both like in the screenshot above) at shutdown when removing plymouth (using esc). I think that I may have seen other symbols but really not sure, I don't record all my shutdowns... It's a Fedora install with encrypted root (and /boot).

shutdown text displayed

I have noted the same, but less frequently on another brand new Fedora install on another laptop (same encrypted set-up). I have not found a whole lot of info online, apart from the below links:

Ubuntu is freezing - why and what does this symbol mean ^@?

(^@ is the null byte. A sequence of them usually means a file was shortened while another process was still writing to it, so the missing part was replaced by nulls)

System crash - strange chars in syslog

(Your system crash caught the system mid-writing to the syslog file, and that is the end result. PS getting into anecdotal territory, last time I had this happening regularly in a Banana Pi R1, I managed to trace the cause to a (faulty) realtek wifi chipset.)

Characters like @ at shutdown

(issue happened to all his laptops and then disappeared)

These characters cannot be found in journald nor anywhere else I looked. My system is stable, never had it crash on me and it's a relatively clean install (installed F36 2 mo ago and did not install anything special). I recall first noticing it reasonably soon after the fresh install. It seems to appear slightly less often if:

  • I don't use plymouth (eg. remove splash)
  • I reboot / poweroff shortly after starting up my laptop (less processes running?)
  • I poweroff using the GUI instead of the command line

I don't think that appears when I shutdown from a tty after logging out from the graphical session (Gnome).

So putting together all of the above, seems to me that it may be possibly linked to shutting down an encrypted system or somehow related to the GUI though I don't recall seeing this when I was using Ubuntu on the same laptop with the same encrypted set-up. System shuts down in a few seconds.

Any thoughts welcome.

Huria
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  • "These characters cannot be found in journald nor anywhere else I looked": how did you look? You can't grep for ^@, for example, you need to grep for $'\0'. – terdon Sep 21 '22 at 08:17
  • To my experience, cleanly und quickly shutting down a system is hard work, harder than booting it up, because you have a similar set of dependencies, but additionally unknown states of many components. To avoid situations where a system gets completely stuck in a shutdown deadlock, you usually add timeouts, after which processes get force-killed and power supplies get turned off. Those are the situations where NULL bytes and other rubbish can get generated. Hard to debug, and unlikely to be worth the effort. – Philippos Sep 21 '22 at 11:05
  • Thanks for the answers! terdon, thanks. I'm not getting anything with journalctl -b -1 (or 2 or whatever) | grep $'\0' or any variation. Previously, I looked going through all of the shutdown messages on both journalctl & the log GUI programme for several sessions and did not see anything that would seem of relevance.

    Philippos, thanks. I'm not necessarily looking to debug, more to understand why something like this would happen and whether I need to worry. It does not seem so from what I could find so far.

     – Huria Sep 21 '22 at 18:59
  • For whatever it's worth, as I continue to keep an eye out on this, I note that it never shows these characters when I log in to a tty and shutdown from there, regardless of what I was doing in the graphical session. – Huria Oct 31 '22 at 20:57

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