When debugging a problem before, I encountered systemd-shutdown with suppressed logs, but I have not found a way to do it.
https://bbs.archlinux.org/viewtopic.php?id=250822
Searched again, it turned out to be set through sysctl:
printk_devkmsg: Control the logging to /dev/kmsg from userspace:
ratelimit: default, ratelimited ;;; this is the default value; there is a limit on the speed of the log
on: unlimited logging to /dev/kmsg from userspace; no limit
off: logging to /dev/kmsg disabled; turn off log printing
The kernel command line parameter printk.devkmsg= overrides this and is a one-time setting until next reboot: once set, it cannot be changed by this sysctl interface anymore.
This value cannot be modified in real time, it can only be set at startup .
An example of shutdown:
https://bugzilla.redhat.com/show_bug.cgi?id=2178942
2023-03-14