linux下使用shred安全地删除文件

    shred  安全地删除文件

shred可覆盖文件以隐藏内容，另外还可以删除文件

#[root@test]shred -zvu -n 5 test.txt

这个命令包括的几个选项有：

• -z – 最后一次覆盖添加0，以隐藏覆盖操作
• -v – 能够显示操作进度
• -u – 覆盖后截断并删除文件
• -n – 指定覆盖文件内容的次数(默认值是3次)
• Usage: shred [OPTION]... FILE...
  Overwrite the specified FILE(s) repeatedly, in order to make it harder
  for even very expensive hardware probing to recover the data.
  
  Mandatory arguments to long options are mandatory for short options too.
    -f, --force    change permissions to allow writing if necessary
    -n, --iterations=N  overwrite N times instead of the default (3)
        --random-source=FILE  get random bytes from FILE
    -s, --size=N   shred this many bytes (suffixes like K, M, G accepted)
    -u, --remove   truncate and remove file after overwriting
    -v, --verbose  show progress
    -x, --exact    do not round file sizes up to the next full block;
                     this is the default for non-regular files
    -z, --zero     add a final overwrite with zeros to hide shredding
        --help     display this help and exit
        --version  output version information and exit
  
  If FILE is -, shred standard output.
  
  Delete FILE(s) if --remove (-u) is specified.  The default is not to remove
  the files because it is common to operate on device files like /dev/hda,
  and those files usually should not be removed.  When operating on regular
  files, most people use the --remove option.
  
  CAUTION: 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.  The following are examples of file systems on which shred is
  not effective, or is not guaranteed to be effective in all file system modes:
  
  * log-structured or journaled file systems, such as those supplied with
  AIX and Solaris (and JFS, ReiserFS, XFS, Ext3, etc.)
  
  * 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
  
  In the case of ext3 file systems, the above disclaimer applies
  (and shred is thus of limited effectiveness) only in data=journal mode,
  which journals file data in addition to just metadata.  In both the
  data=ordered (default) and data=writeback modes, shred works as usual.
  Ext3 journaling modes can be changed by adding the data=something option
  to the mount options for a particular file system in the /etc/fstab file,
  as documented in the mount man page (man mount).
  
  In addition, file system backups and remote mirrors may contain copies
  of the file that cannot be removed, and that will allow a shredded file
  to be recovered later.
  
  Report shred bugs to [e-mail]
  GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
  General help using GNU software: <http://www.gnu.org/gethelp/>
  For complete documentation, run: info coreutils 'shred invocation'