Friday, 12 February 2010

File Deletion using "Shred"

shred: Delete a file securely, first overwriting it to hide its contents.

It is available on most of Linux distributions including Debian GNU/Linux. To remove file called personalinfo.tar.gz :

$ shred -n 200 -z -u personalinfo.tar.gz


* -n: Overwrite N (200) times instead of the default (25)
* -z: Add a final overwrite with zeros to hide shreddin
* -u: Truncate and remove file after overwriting

Read the man page of shred(1) for more information. Most of these utilities are not effective (read as useless) only if :

* File system is log-structured or journaled filesystems, such as JFS, ReiserFS, XFS, Ext3 etc
* Your filesystems is RAID-based, compressed filesystem etc
* In addition, file system backups and remote mirrors may contain copies of the file that cannot be removed by these utilities.

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