Problem

Looking at your /var/log/syslog you see entries every few seconds like the following:

Mar  1 15:44:52 L530 systemd-udevd[11464]: failed to execute '/lib/udev/socket:@/org/freedesktop/hal/udev_event' 'socket:@/org/freedesktop/hal/udev_event': No such file or directory
Mar  1 15:44:52 L530 systemd-udevd[11451]: Process 'socket:@/org/freedesktop/hal/udev_event' failed with exit code 2.
Mar  1 15:44:54 L530 systemd-udevd[11479]: failed to execute '/lib/udev/socket:@/org/freedesktop/hal/udev_event' 'socket:@/org/freedesktop/hal/udev_event': No such file or directory
Mar  1 15:44:54 L530 systemd-udevd[11466]: Process 'socket:@/org/freedesktop/hal/udev_event' failed with exit code 2.

Solution

Seems that hal is not used in newer Ubuntu versions, so you can remove it:

sudo apt-get purge hal

Taken from the answer here