Shred is a program that will allow under Unix-like systems, secure deletion of files on disk. Various methods such as multiple overwriting be used with bit patterns or random values to make it difficult to recover deleted data or even impossible ( in practical terms ). The command is part of the GNU core utilities.
Shred can not develop at all file systems its effect due to technical circumstances. Among other things, in the following situations data can not reliably be safely deleted:
- If the file system copy on write semantics implemented, for example ZFS
- If a log - structured or " journaled " file system is used, for example, JFS, ReiserFS and XFS.
- If the files on a RAID system ( a hard disk composite ) were stored.
- Create in file systems, snapshots ( snapshots ).
- In compressed file systems.
- For network file systems.
- For file systems on certain flash memories, in which provide wear-leveling algorithms that overwrite existing data, they are stored in a different physical address of the memory.