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Old 06-21-2004, 07:05 PM   #1
bun_zee
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Registered: Jun 2004
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secure delete journal


Hi,

Shred is a secure delete utility that comes with RH Linux. The shred man page say that it does not work well with filesystem that use journaling.

I read a few articles in journaling. One of the article said "When metadata on the disk is updated, the updates are recorded in a separate area of the disk reserved for use as a journal. Filesystem transactions which complete have a commit record added to the journal, and only after the commit is safely on disk may the filesystem write the metadata back to its original location. Transactions are atomic because we can always either undo a transaction (throw away the new data in the journal) or redo it (copy the journal copy back to the original copy) after a crash, ac-cording to whether or not the journal contains a commit record for the transaction."

From this article, I dont quite understand why journaling is an issue in shred.

Journaling is meant for recovery when the system loss power abruptly. When this is the case, the file won't be overwritten properly which is true with or without journaling. It is not like journalling is going to "write data in a different data blocks" or something.

Many articles claimed that journaling is an issue in shred without any real in depth explanation.

QUESTION:
Could any one please explain why journaling is an issue in secure delete?
A sample scenario would be nice!
Also, if journaling is indeed pose complication, then would this help at all:
mount -t ext3 -o data=writeback /dev/sda2 /jdisk
(Basically this mount the with the writeback mode for ext3).

Any response is appreciated.

Thank you,

BunZ
 
Old 06-21-2004, 07:10 PM   #2
wapcaplet
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Registered: Feb 2003
Location: Colorado Springs, CO
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I'm afraid I can't offer much in the way of technical details, but there was a related question a while back. I don't know if using the writeback option would help, but I guess you could probably mount the filesystem as ext2, do your secure deletions, then remount as ext3 again.
 
  


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