wipe utility

[James R. Van Zandt]

 Cole Tuininga wrote:
 ...
 | Keep in mind that it is completely useless on any journaling filesystem
 | (such as linux's ext3).

The GNU coreutils include "shred" which overwrites a file.  Its man
page says "The following are examples of filesystems on which shred is
not effective: ... log-structured or journaled filesystems, such as
those supplied with AIX and Solaris (and JFS, ReiserFS, XFS, Ext3,
etc.) ... "

dsr at tao.merseine.nu noted the following mount options for ext3:
>
>      data=journal / data=ordered / data=writeback
>
>         Specifies  the  journalling  mode  for  file data.
>         Metadata is always journaled.
>
>         journal
>
>             All data is committed into the journal prior to being
>             written into the main file system.
>
>         ordered
>
>             This is the default mode.  All data is forced directly
>             out to the main file system prior to its metadata being
>             committed to the journal.
>
>         writeback
>
>             Data ordering is not preserved - data may be written
>             into the main file system after its metadata has been
>             committed to the journal.  This is rumoured to be the
>             highest-through)B­put option.  It guarantees internal
>             file system integrity, however it can allow old data to
>             appear in files after a crash and journal recovery.

As I interpret this, "wipe" will work with any of these journaling
modes to overwrite data at its primary location on the disk.  However,
with "data=journal" there may be another copy of the data in the
journal that "wipe" would not reach.

		- Jim Van Zandt