shred - linux command to delete file

Deletes a file securely by overwriting its contents
shred -v filename (replace filename with your specific file)
The -v option is useful since it provides extra view of what exactly the shred tool is doing while you wait. On especially BIG files this could take a bit of time. The result is that your file is so thoroughly deleted it is very unlikely to ever be retrieved again. This is especially useful when trying to zap important server related files that may include confidential information like user names or hidden processes.

[root@vikas Desktop]# whatis shred
shred (1) - overwrite a file to hide its contents, and optionally delete it
[root@vikas Desktop]#