Comment 0 for bug 1342875

A user can not delete themselves using the command 'sudo userdel -rf <username>', this is common in cloud tools that clean up running images prior to capture. A quick test shows that this worked from Precise (didn't look back further) to Raring and stopped working with Saucy.

Here's a quick example of the failure (from trusty):
# sudo adduser test
# sudo usermod -aG sudo test
## As the 'test' user
# sudo userdel -rf test
userdel: user test is currently used by process 9600
userdel: cannot open /etc/subuid
## User is not removed

Previously (output from precise)
# sudo userdel -rf test
userdel: user test is currently logged in
userdel: warning: can't remove /var/mail/test: No such file or directory
## User is removed

This is being run as the last command by tools that remove the 'ubuntu' user to clean the image prior to capture. This had previously worked and it is preferable that this could be made to work again. The alternative is removal by root, but the root user on cloud images is locked down and we would not want the user to enable root to run userdel on the risk of it not getting disabled properly prior to image capture.