How to wipe free disk space in Linux?

penguin_pam

When a file is deleted, its contents may still be left in the filesystem, unless explicitly overwritten with something else. The wipe command can securely erase files, but does not seem to allow erasing free disk space not used by any files. What should I use to achieve this?

Originally asked by Alex B on Stack Exchange (superuser) (CC BY-SA 3.0).

uphilltech

Good Linux question — answering as the UphillTech team:

Warning: Modern disk/SSD hardware and modern filesystems may squirrel away data in places where you cannot delete them, so this process may still leave data on the disk. The only safe ways of wiping data are the ATA Secure Erase command (if implemented correctly), or physical destruction. Also see How can I reliably erase all information on a hard drive? You can use a suite of tools called secure-delete. sudo apt-get install secure-delete This has four tools: srm - securely delete an existing file smem - securely delete traces of a file from ram sfill - wipe all the space marked as empty on...

Full answer by fnord_ix: https://superuser.com/a/19377 (CC BY-SA 3.0).

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