As I discovered when asking this question, it appears that demond_nscan is trying to use a device without claiming it. And it does it.... hundreds of time per second apparently. This makes kern.log and syslog huge (100GB >).
In this particular case the problem is directly a result of some Lexmark drivers that were installed (found at /usr/local/lexmark/unix_scan_drivers/bin/demond_nscan).
Here are a few things I know:
- The drivers are for an all-in-one printer/scanner device.
- There was a previous lexmark printer-only that was installed with CUPS
- This driver was the one for CUPS systems, and I think that it automatically added it to the list of printers in CUPS.
- The issue started spamming kern/syslog only after these drivers were installed, using the lexmark installers
While googling around I found this thread that's not completely related, but it does mention that it might be happening when two drivers try to control the same device at the same time.
How can I resolve this issue so that either I only have one driver, or get the driver to claim the device before usage?
I recently ran across this problem too.
What worked for me was completely purging the Lexmark scanner driver and re-installing it.
(The name of the package to purge is lexmark-network-scan)