HOWTO: Securely Delete Files In Ext3 Via Nautilus Menu

**maynoth** · August 22nd, 2007

This adds a menu which securely deletes files by overwriting them 25 times

install nautilus-actions via synaptic package manager

launch nautilus actions configuration
-->system--->preferences--->nautilus actions configuration

Add

Label = Shred

Path = /usr/bin/find

Parameters = %M -type f -exec shred -f -u -z '{}' \;

Conditions (files and folders) = Both
Click ok and exit

in terminal type killall nautilus

Viola!

A note for ext3 users from the shred manual:
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 sys‐
tem modes:

In the case of ext3 file systems, the above disclaimer applies 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.

**analoog** · June 21st, 2008

can anyone explain me the

Code:

%M -type f -exec shred -f -u -z '{}' \;" command?

Are the -f and -z srm parameters? what does - u do?
what does %M -type f -exec mean?

**maynoth** · July 10th, 2008

%M: space-separated list of the selected file(s)/folder(s) with their full paths

The " -type f " option for find indicates that the files should be plain, as opposed to links, directories, etc.

-exec shred starts the shred command

-f, --force
change permissions to allow writing if necessary

-u, --remove
truncate and remove file after overwriting

-z, --zero
add a final overwrite with zeros to hide shredding

'{}' \; within directory tree

**adlibre** · August 18th, 2009

This is a good, useful tip. I was freaked out by the idea that I could shred things so easily, so I wanted to add a confirmation box. Here's how to do it.

First, install zenity (displays GUI dialogs via GTK)

Code:

sudo apt-get install zenity

Next paste the script below into a file called shred_it.sh and put it somewhere convenient (e.g. /home/user/bin/shred_it.sh)

Code:

#!/bin/bash
# shred_it.sh: shred a selected file in nautilus through nautilus-actions

# quit if no arguments are passed
if [ $# != 1 ]; then
    exit 1
fi
if !  zenity  --question --title "shred"  --text "Permanently delete?\n$1" ; then
    # cancel deleting
    exit 0
else 
    # shred selected file
    # Optional:
    #    - change 7 to 25 for more iterations
    #    - add -z after shred command to hide shredding
    shred -f -u -n 7 "$1"
fi

Finally, change the path and parameters in Nautilus Actions Configuration for your shred action:

- Path: /usr/bin/find
- Parameters: %M -type f -exec /home/user/bin/shred_it.sh '{}' \;
(make sure you use a capital M above)

Due to limitations described below, this script is only good for working on single files (not folders or multiple files). Be sure to select "Appears if selection contains: Only files" under "Conditions" for your action profile.
Lastly, refresh nautilus to see changes:

Code:

killall nautilus

And that's it, no need to wait for this "feature" in Ubuntu.

Limitations:
- You can only delete one file at a time. Extending this script to work with multiple files would not be too difficult. You would need to check the option "Appears if selection has multiple files or folders" under the Conditions tab for the shred action. Then you would need to modify the script so that it does not ask for a "confirm delete" each time. Similarly you could modify the script to delete an entire folder. I experimented with these versions of the script, but I became worried about passing "bad filenames" to the script and the damage this could possibly do (see below), so I decided to post this simpler version instead.
- Be careful when using scripts like these to work on files with weird/non-standard characters (newlines, tabs, leading dashes, etc). These can make your script behave in unexpected ways and possibly do major damage. For more details as to why this is, see this very detailed article (if you're familiar with shell programming):
http://www.dwheeler.com/essays/fixing-unix-linux-filenames.html
If you modify this script to delete multiple files/directories, think carefully about checking the filenames passed from nautilus-actions to your script and make sure the filenames don't contain non-standard characters before attempting to delete them. As the article above makes clear, this is more complicated than you may think...

**x-shaney-x** · August 18th, 2009

I find if I use this script I have to do the process twice before anything is deleted.

**adlibre** · August 18th, 2009

Hmm, I'm not sure why you would have to do it twice. Perhaps Nautilus is just not refreshing -- try pressing F5 after you shred something...

**x-shaney-x** · August 18th, 2009

Not sure what the problem is, maybe I wasn't leaving it long enough to do it's job but it appears to be working ok now.

**viking_maniac** · August 29th, 2009

Do you really need to securely delete files on the Ext3 file system with shred? Ext3 does this by default by overwriting the deleted data area with zeros.

Filesystems
Starting with ext3, Linux filesystems overwrite files with zeros when you delete them, rather than just marking the file as “free space.” Previous Linux filesystems, as well as the Windows filesystems (NTFS, FAT) use the latter method, which is why it is so easy to recover deleted files with software tools freely downloadable on the Internet. This is something to consider when deciding how much time you should spend wiping your drive.

http://www.techthrob.com/2009/03/02/...rely-in-linux/