How could I totally destroy any file with no possibilities of restoration?
In Linux, after deleting a file I don’t think there is a way to recover it… Yes, there are few recovery tools but still most of them very hard to recover.
Check out the man page for shred. The program will overwrite with data after deleting.
Normally, by default you can not recover deleted file
you can purge content of file before removing it by “shred”
see man page of shred
There is BleachBit for some Linux OS’s that has a file overwrite option, however this is not advisable when one’s running a SSD. On a HDD only, it’s fine.
On the forum where I participate the most & am an Advisor at (Bleeping Computer), we tend not to recommend ‘cleaners’ for LInux OS’s. Particularly to new users, those Temp files at most uses only 200-300MiB of space, the chance of breaking the OS is not worth that much gained space.
For an experienced user whom knows what’s going on, BleachBit can be a useful tool, when used in moderation.
If one really wants to ‘shred’ behind themselves, like a transaction or personal business, just use the latest install DVD, not a Flash drive, as the DVD is finalized & can’t be written to. Once one’s business is done, reboot & it’s like the entire session never took place, it resides in the RAM & the reboot flushes all.
I always make my purchases & financial deals using the latest install media.
Another way to trash items in a secure manner is to use 7zip to encrypt the unwanted files & then delete it. Even if it was found, w/out the encryption password, would be useless, no one can see inside. Use AES-256 encryption, it works on any OS.
Hope this is of assistance.
You can use shred tool to delete a file forever
shred -fuvz file
or fill the file with zeros using dd command
#dd if=/dev/zero of=/home/user/file