Comment 8 for bug 1456670

I also encountered this on a xenial machine where the upgrade somehow was broken, and 'apt install' would give the following errors:

Preconfiguring packages ...
Setting up util-linux (2.27.1-6ubuntu3.2) ...
insserv: Service mountdevsubfs has to be enabled to start service hwclock
insserv: exiting now!
update-rc.d: error: insserv rejected the script header
dpkg: error processing package util-linux (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 util-linux
E: Sub-process /usr/bin/dpkg returned an error code (1)

The solution for us was to run

'dpkg-reconfigure initscripts'

and

'apt install'

to configure the large amount of unconfigured remaining packages.

Not sure why it happened, but i am guessing something was upgraded and configured in the wrong order.

It works fine again after our solution.