如果要彻底删除硬盘上的文件，Windows下有磁盘粉碎机，bcwipe等。

Linux下，也有bcwipe，而且功能更强大。

擦除磁盘剩余空间：

bcwipe -Fvmd /

上面的F是擦出剩余空间，不删除已有文件，/是挂载的根目录。md是擦除方式，可选的有如下：

  -mb       German BCI/VISTR 7-pass wiping
  -md       U.S. DoD 5220-22M 7-pass extended character rotation wiping
  -me       U.S. DoE 3-pass wiping
  -mf<file> read wiping scheme from file. See *notes below
  -mg       (default) 35-pass wiping by Peter Gutmann
  -ms       7-pass wiping by Bruce Schneier
  -mt       1-pass test mode: fill the start of 512-byte block with block number
  -mz       1-pass zero wiping
  -m N      U.S. DoD 5220-22M N-pass extended character rotation wiping