on my sandbox VM (Oracle Linux 7.2) that I boot not every day and just "yum update" occasionally today I found out
that systemd, systemd-udevd and systemd-logind repeatedly spam my dmesg output, e.g:
# dmesg
[10761.391100] systemd-udevd[487]: cleanup idle workers
[10761.391156] systemd-udevd[487]: Validate module index
[10761.391174] systemd-udevd[487]: Check if link configuration needs reloading.
[10761.391213] systemd-udevd[6181]: Unload module index
[10761.391228] systemd-udevd[6182]: Unload module index
[10761.391237] systemd-udevd[6181]: Unloaded link configuration context.
[10761.391246] systemd-udevd[6182]: Unloaded link configuration context.
[10761.391335] systemd-udevd[6180]: Unload module index
[10761.391351] systemd-udevd[6180]: Unloaded link configuration context.
[10761.391636] systemd-udevd[487]: worker [6182] exit
[10761.391639] systemd-udevd[487]: worker [6182] cleaned up
[10761.391646] systemd-udevd[487]: worker [6180] exit
[10761.391648] systemd-udevd[487]: worker [6180] cleaned up
[10761.391905] systemd-udevd[487]: worker [6181] exit
[10761.391907] systemd-udevd[487]: worker [6181] cleaned up
[...]
[10810.228493] systemd[1]: Collecting session-20.scope
[10810.228505] systemd[1]: Sent message type=signal sender=n/a destination=n/a object=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=UnitNew cookie=5548 reply_cookie=0 error=n/a
[10810.228513] systemd[1]: Sent message type=signal sender=n/a destination=n/a object=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=UnitRemoved cookie=5549 reply_cookie=0 error=n/a
[10810.228600] systemd[1]: Got disconnect on private connection.
[10810.229016] systemd-logind[628]: Removed session 20.
[10810.229093] systemd-logind[628]: Sent message type=signal sender=n/a destination=n/a object=/org/freedesktop/login1 interface=org.freedesktop.login1.Manager member=SessionRemoved cookie=284 reply_cookie=0 error=n/a
[10810.229302] systemd-logind[628]: Sent message type=signal sender=n/a destination=n/a object=/org/freedesktop/login1/user/_0 interface=org.freedesktop.DBus.Properties member=PropertiesChanged cookie=285 reply_cookie=0 error=n/a
[10810.229439] systemd-logind[628]: Got message type=signal sender=:1.0 destination=n/a object=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=UnitRemoved cookie=5546 reply_cookie=0 error=n/a
[10810.229463] systemd-logind[628]: Got message type=signal sender=:1.0 destination=n/a object=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=UnitRemoved cookie=5549 reply_cookie=0 error=n/a
For me this seems like messages, that nobody really needs or cares about.
Just repeated messages of "oh look, I'm doing this, I'm doing that. I'm just doing what my job is. Nothing worth to mention but I repeatedly tell you. Enjoy".
Is there a way to set the debug level of this 3 noisy brats lower?