Shred doesn't operate on free space at all. It overwrites the file, and assumes that the underlying filesystem will overwrite the data in place. http://www.gnu

Shred doesn't operate on free space at all. It overwrites the file, and assumes that the underlying filesystem will overwrite the data in place. http://www.gnu.org/software/coreutils/manual/html_node/shred-invocation.html http://www.gnu.org/software/coreutils/manual/html_node/shred... "Please note that shred relies on a very important assumption: that the file system overwrites data in place. This is the traditional way to do things, but many modern file system designs do not satisfy this assumption. Exceptions include: Log-structured or journaled file systems, such as those supplied with AIX and Solaris, and JFS, ReiserFS, XFS, Ext3 (in data=journal mode), BFS, NTFS, etc., when they are configured to journal data. File systems that write redundant data and carry on even if some writes fail, such as RAID-based file systems. File systems that make snapshots, such as Network Appliance's NFS server. File systems that cache in temporary locations, such as NFS version 3 clients. Compressed file systems."