Use of sfill -l ~; is it actually doing anything?

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Use of sfill -l ~; is it actually doing anything?

Owen Thomas
Helleaugh....

I'm using sfill to get rid of some naughty bits. I put sfill -l to work on my home directory at about 2pm (about 7 hours ago) today, and it is still chugging away. I'm running Ubuntu 16.04 on my Dell Latitude E5570 laptop. The disk is 900GB in capacity and according to the System Monitor 26GB or 2% (apparently) is being used. Disk usage analyser says my home directory consumes 18.6GB. There was a small break of about an hour or so when I put my computer on standby.

Is sfill actually doing anything, and if it is, when should I expect it to finish?

Thanks,

  Owen.


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Re: Use of sfill -l ~; is it actually doing anything?

ubuntu-users mailing list
On Wed, 16 Oct 2019 21:01:46 +1100, Owen Thomas wrote:
>Is sfill actually doing anything, and if it is, when should I expect
>it to finish?

To see if it is still running, run

$ ps aux | grep sfill

to see if it might use an unusual amount of resources run

$ top

to actually see if it's still writing run

sudo iotop -o

https://askubuntu.com/questions/961558/how-to-know-the-progress-of-sfill-free-space-wiping-process



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Re: Use of sfill -l ~; is it actually doing anything?

ubuntu-users mailing list
PS:

On Wed, 16 Oct 2019 12:24:31 +0200, Ralf Mardorf wrote:
>https://askubuntu.com/questions/961558/how-to-know-the-progress-of-sfill-free-space-wiping-process

Please do not ignore the link "probably a waste of time" ( https://www.howtogeek.com/115573/htg-explains-why-you-only-have-to-wipe-a-disk-once-to-erase-it/ )
provided by the above link.



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Re: Use of sfill -l ~; is it actually doing anything?

Owen Thomas
On Wed, 16 Oct 2019 at 21:34, Ralf Mardorf via ubuntu-users <[hidden email]> wrote:
PS:

On Wed, 16 Oct 2019 12:24:31 +0200, Ralf Mardorf wrote:
>https://askubuntu.com/questions/961558/how-to-know-the-progress-of-sfill-free-space-wiping-process

Thanks Ralf. I had actually read that page. I'm cleaning my disk before I find someone to repair the computer; it has a swollen battery and a fan that doesn't work. The weather is soon to warm up here, so I'm going to try to save it before the approaching summer claims it.

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Re: Use of sfill -l ~; is it actually doing anything?

ubuntu-users mailing list
In reply to this post by Owen Thomas
On Wed, 16 Oct 2019 21:01:46 +1100, Owen Thomas wrote:
>The disk is 900GB in capacity and according to the System Monitor 26GB
>or 2% (apparently) is being used.
>when should I expect it to finish?

The manual page mentions this:

"The secure data deletion process of sfill goes like this:

       *      1 pass with 0xff

       *      5 random passes. /dev/urandom is used for a secure RNG if
              available.

       *      27 passes with special values defined by Peter Gutmann.

       *      5 random passes. /dev/urandom is used for a secure RNG if
              available.

       afterwards as many temporary files as possible are generated to
       wipe the free inode space. After no more temporary files can be
       created, they are removed and sfill is finished." -
http://manpages.ubuntu.com/manpages/xenial/man1/sfill.1.html

Then do the calculation:

An example using GiB instead of GB, you need to do the calculation for
GB yourself.

(1pass+5passes+27passes+5passes)*(900GiB capacity-26GiB used)=33212GiB

33212GiB/1024=32.43TiB

How long it takes to write around 32 TiB depends on the used hardware
and the I/O handling of the software. Likely the theoretical B/s max.
value has got nothing to do with realistic averaged values.

However, perhaps you already have used gparted to resize and move
partitions on you 900 GiB sized HDD. When doing so data gets copied,
IOW read and written, perhaps tens or hundreds of GiB. This could take
very long for those GiB, so writing tens of TiB takes many times over
very long.

Keep in mind you are most likely overwriting the data multiple times for
esoteric reasons only.


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Re: Use of sfill -l ~; is it actually doing anything?

ubuntu-users mailing list
In reply to this post by Owen Thomas
On Wed, 16 Oct 2019 21:55:46 +1100, Owen Thomas wrote:
>I'm cleaning my disk before I find someone to repair the computer

Somebody who owns a magnetic force microscope and/or a laser thingy, a
cleanroom and is willing to spend a very long time to reconstruct data?
If reconstructing data should be possible at all, after overwriting data
just a single time or after overwriting it two or three times, it still
would require special gear and much time to do so. Nobody would do it
to get medical patient data, an adult movie collection or something
similar. I even doubt that intelligence agencies consider to
reconstruct data that was only overwritten 1, instead of 38 times.


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Re: Use of sfill -l ~; is it actually doing anything?

Owen Thomas
Although my laptop has only been effectively running for about four hours today, it is still going! Surely some type of progress indicator can be put into the program?


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Re: Use of sfill -l ~; is it actually doing anything?

Liam Proven
In reply to this post by Owen Thomas
On Wed, 16 Oct 2019 at 12:04, Owen Thomas <[hidden email]> wrote:
>
> Helleaugh....
>
> I'm using sfill to get rid of some naughty bits.

Read this to the end:

https://www.blancco.com/blog-many-overwriting-rounds-required-erase-hard-disk/

The 3/6/7/10 overwrite stuff is superstition.

Once is enough.

Sadly DBAN is commercial now. KillDisk is free though.
https://www.killdisk.com/eraser.html

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