From Newsgroup: alt.os.linux.ubuntu

Just what subject says, I need a utility to scramble/ overwrite deleted
file space to make the files unrecoverable. I just read about Shred,
but it requires moving all existing files off of the drive first, then
doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you
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From Newsgroup: alt.os.linux.ubuntu

On Wed, 11 Mar 2026 22:38:31 -0400, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted
file space to make the files unrecoverable. I just read about Shred,
but it requires moving all existing files off of the drive first, then
doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

If you have a ssd just issue the trim command.
--
Pull my finger
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From Newsgroup: alt.os.linux.ubuntu

On Wed, 3/11/2026 10:38 PM, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted file space to make the files unrecoverable.  I just read about Shred, but it requires moving all existing files off of the drive first, then doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

1) Unmount partition /dev/sdb2 # Can't have target partition mounted while this runs

2) sudo zerofree /dev/sdb2 # Writes the unallocated space, removing deleted material evidence

For the slash partition, boot with a LiveDVD (slash is now unmounted)
and try it out. The default fill is zeros, which is a good choice.

https://manpages.ubuntu.com/manpages/focal/man8/zerofree.8.html

sudo zerofree /dev/sdb2 # Zero out unmounted EXT family partition and its unallocated blocks
# Any undeleted files will not be touched
# Typical usage:
# Used just before doing a compact on a VHD container with EXtn inside
# Also used to zero unused parts of /dev/sdb2 before the usage of a dd.gz backup op.
# Zero the EXTn on /dev/sdb one at a time, then sudo dd and pipe to a compressor.

While backing up with "dd" is a pretty time-wasting thing to do,
it's part of preparing for the test of other backup programs. You
make "dd" backups because you know they work. Does NOT support resize particularly. dd tends to be for "like-to-like" situations (requires
lowest skill level of the user).

Anything requiring physical layer access to storage, needs elevation.
The compressor doesn't need to be elevated, as it comes later.

Zerofree does not support a very wide selection of partition types,
but I can still fit this into a workflow.

Example: 1TB drive with 20GB worth of OS files. Zerofree.
dd | then pipe to compressor, output file would be 20GB or less in size.
A good approach for partially filled partitions. All of the zeros,
can compress quite well.

Paul
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From Newsgroup: alt.os.linux.ubuntu

On 12/03/2026 02:38, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted
file space to make the files unrecoverable. I just read about Shred,
but it requires moving all existing files off of the drive first, then
doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

<https://docs.bleachbit.org/doc/shred-files-and-wipe-disks.html>

It's quite a lot to read, but worth spending the time on.
--
Jeff
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From Newsgroup: alt.os.linux.ubuntu

On Thu, 12 Mar 2026 02:34:36 -0400, Paul wrote:

While backing up with "dd" is a pretty time-wasting thing to do,
it's part of preparing for the test of other backup programs. You
make "dd" backups because you know they work.

Use rsync for backups. It has a --checksum option that lets you verify
the backup afterwards. What has dd got?

They don’t call it the “data destroyer” for nothing ...
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From Newsgroup: alt.os.linux.ubuntu

On 3/12/26 03:38, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted
file space to make the files unrecoverable.  I just read about Shred,
but it requires moving all existing files off of the drive first, then
doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

I usually create a file as root using all available free disk space:
dd if=/dev/zero of=/zerofile bs=128k; rm -f /zerofile
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From Newsgroup: alt.os.linux.ubuntu

On 3/12/26 03:38, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted
file space to make the files unrecoverable.  I just read about Shred,
but it requires moving all existing files off of the drive first, then
doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

It depends upon the contents of that deleted files: if they contain the
codes for some ICBMs or the passwords and access codes to some
multi-billion fortune, ask somebody else.

For us mere mortals:

Create a file as root using all available free disk space:
dd if=/dev/zero of=/zerofile bs=128k; rm -f /zerofile

Josef
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From Newsgroup: alt.os.linux.ubuntu

On 3/12/26 2:34 AM, Paul wrote:

On Wed, 3/11/2026 10:38 PM, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted file space to make the files unrecoverable.  I just read about Shred, but it requires moving all existing files off of the drive first, then doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

1) Unmount partition /dev/sdb2 # Can't have target partition mounted while this runs

2) sudo zerofree /dev/sdb2 # Writes the unallocated space, removing deleted material evidence

For the slash partition, boot with a LiveDVD (slash is now unmounted)
and try it out. The default fill is zeros, which is a good choice.

https://manpages.ubuntu.com/manpages/focal/man8/zerofree.8.html

sudo zerofree /dev/sdb2 # Zero out unmounted EXT family partition and its unallocated blocks
# Any undeleted files will not be touched
# Typical usage:
# Used just before doing a compact on a VHD container with EXtn inside
# Also used to zero unused parts of /dev/sdb2 before the usage of a dd.gz backup op.
# Zero the EXTn on /dev/sdb one at a time, then sudo dd and pipe to a compressor.

While backing up with "dd" is a pretty time-wasting thing to do,
it's part of preparing for the test of other backup programs. You
make "dd" backups because you know they work. Does NOT support resize particularly. dd tends to be for "like-to-like" situations (requires
lowest skill level of the user).

Anything requiring physical layer access to storage, needs elevation.
The compressor doesn't need to be elevated, as it comes later.

Zerofree does not support a very wide selection of partition types,
but I can still fit this into a workflow.

Example: 1TB drive with 20GB worth of OS files. Zerofree.
dd | then pipe to compressor, output file would be 20GB or less in size.
A good approach for partially filled partitions. All of the zeros,
can compress quite well.

Paul

Unfortunately, I neglected to mention that both attached USB drives are
NTFS, so it doesn't appear that the Zerofree will work with them. So,
same as above request except for NTFS. Sorry!
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From Newsgroup: alt.os.linux.ubuntu

On Thu, 3/12/2026 7:38 AM, JR Dolobson wrote:

On 3/12/26 2:34 AM, Paul wrote:

On Wed, 3/11/2026 10:38 PM, JR Dolobson wrote:

Just what subject says, I need a utility to scramble/ overwrite deleted file space to make the files unrecoverable.  I just read about Shred, but it requires moving all existing files off of the drive first, then doing a drive overwrite and/or overwriting the file no longer wanted.

Thank you

1) Unmount partition  /dev/sdb2     # Can't have target partition mounted while this runs

2) sudo zerofree /dev/sdb2          # Writes the unallocated space, removing deleted material evidence

For the slash partition, boot with a LiveDVD (slash is now unmounted)
and try it out. The default fill is zeros, which is a good choice.

https://manpages.ubuntu.com/manpages/focal/man8/zerofree.8.html

     sudo zerofree /dev/sdb2     # Zero out unmounted EXT family partition and its unallocated blocks
                                 # Any undeleted files will not be touched
                                 # Typical usage:
                                 #   Used just before doing a compact on a VHD container with EXtn inside
                                 #   Also used to zero unused parts of /dev/sdb2 before the usage of a dd.gz backup op.
                                 #      Zero the EXTn on /dev/sdb one at a time, then   sudo dd   and pipe to a compressor.

While backing up with "dd" is a pretty time-wasting thing to do,
it's part of preparing for the test of other backup programs. You
make "dd" backups because you know they work. Does NOT support resize
particularly. dd tends to be for "like-to-like" situations (requires
lowest skill level of the user).

Anything requiring physical layer access to storage, needs elevation.
The compressor doesn't need to be elevated, as it comes later.

Zerofree does not support a very wide selection of partition types,
but I can still fit this into a workflow.

Example: 1TB drive with 20GB worth of OS files. Zerofree.
          dd | then pipe to compressor, output file would be 20GB or less in size.
          A good approach for partially filled partitions. All of the zeros,
          can compress quite well.

    Paul

Unfortunately, I neglected to mention that both attached USB drives are NTFS, so it doesn't appear that the Zerofree will work with them.  So, same as above request except for NTFS.  Sorry!

For NTFS, use sdelete on Windows.

https://learn.microsoft.com/en-us/sysinternals/downloads/sdelete

sdelete64.exe -z C: # One pass of zeros, over white space, then cleans $MFT unused slots

Note that sdelete can fail some cleaning tests, and
you have to be pretty careful to not issue a test command and
pollute what you are working on, when developing test cases
for it. The text in the above web page, describes some of the
limitations with cleaning.

In general, a computer is not a good place to be doing things
requiring a measure of privacy. It's too easy to screw up and
leave stuff behind.

*******

For Windows, there is Heidi Eraser, which is a runtime tool
for house cleaning. It is attempting to clean files as
they are deleted. It took at least a couple of years, for
bug reports about "cluster tips not erased" and so on.
Never underestimate the difficulty of cleaning a disk drive
in that way.

https://en.wikipedia.org/wiki/Eraser_%28software%29

Approaches like this are unlikely to function well
under WINE. We're too close to the metal for that. The
underlying file system could be different.

Mainly, my experiments have shown me, that I'm just not
careful enough, to be any good at this stuff.

Paul
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