systemd-udevd[381]: failed to execute '/lib/udev/socket:@/org/fre edesktop/hal/udev_event'

In a fresh installation, this issue won't appear. But it does in upgrades, because Ubuntu deprecated HAL and they are not using it anymore. Maybe they should have mentioned in the upgrade process to remove HAL, but they didn't.

So you can remove it with:

sudo apt-get remove hal

Then you can restart your PC.

After some research, I came to know the reason that they have removed HAL: to improve the boot speed, and speed resume from suspended sessions.

Just removing hal won't help because the config files remain. You need to purge the lot.

sudo apt-get purge hal

https://bugs.launchpad.net/ubuntu/+source/hal/+bug/1182801/comments/3