We can use srm to securely delete files on Linux.
Install srm with
sudo apt install secure-delete
We can now securely delete files by running
srm filetodelete.txt
# srm --help
srm v3.1 (c) 1997-2003 by van Hauser / THC <vh@thc.org>
Syntax: srm [-dflrvz] file1 file2 etc.
Options:
-d ignore the two dot special files "." and "..".
-f fast (and insecure mode): no /dev/urandom, no synchronize mode.
-l lessens the security (use twice for total insecure mode).
-r recursive mode, deletes all subdirectories.
-v is verbose mode.
-z last wipe writes zeros instead of random data.
srm does a secure overwrite/rename/delete of the target file(s).
Default is secure mode (38 writes).
You can find updates at http://www.thc.org
Other links for securely erasing drives.
https://www.tomshardware.com/how-to/secure-erase-ssd-or-hard-drive