Safe delete confidential data on Ubuntu server/VPS should be taken care before service termination.
Wipe handle it good to ensure your data secured. It remove files and write null data several time on that disk location to prevent data rescue tools
Install wipe:
sudo apt-get install wipe
Then securely remove folder:
sudo wipe -r /path/to/folder
For quick process (default of 4 passes), use -q option
sudo wipe -r -q /path/to/folder
If you want define number of passes, use -Q, with X is a number
sudo wipe -r -Q X /path/to/folder
Now, it's safely deleted