devh@devh-PC:~$ sudo apt-get -y purge nvidia-331
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-generic linux-image-generic thermald
Use 'apt-get autoremove' to remove them.
The following packages will be REMOVED:
  nvidia-331
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 184 MB disk space will be freed.
(Reading database ... 243902 files and directories currently installed.)
Removing nvidia-331 (331.113-0ubuntu0.1) ...
stop: Unknown job: nvidia-persistenced
userdel: user nvidia-persistenced is currently used by process 1612
dpkg: error processing package nvidia-331 (--remove):
 subprocess installed post-removal script returned error exit status 8
Errors were encountered while processing:
 nvidia-331
E: Sub-process /usr/bin/dpkg returned an error code (1)