I have a firm supplied laptop that I'm going to return because I'm switching job. I'm having backups and deleting personal data from it, but just to be sure I developed this small app that fills all disk space with random sequences of different length, so that deleted data is actually overwritten. It then removes the files it created. A random number of files is created in order to overwrite unused directory buckets (note: this will likely trash your filesystem). Don't forget to clean up all your files before running it. On Win32 machines, you'd better also clean your browser cache and empty your recycle bin before running it. This is a hack, so no warranty whatsoever - use it at your own risk.

Use: launch the script passing the name of a directory where temporary files will be stored.

If you interrupt it for any reason, don't forget to delete the files it created. 


use strict;


my $fp = $ARGV[0] or die "use: cleandisk path\nA path is mandatory";
my $nf = 0;

print "Filling with random data your entire hard disk.\n";

my $randomDataCacheLength = 50000;
my $randomDataCache = load_rdc( $randomDataCacheLength );
my @filesWritten;


my $noError = 1;

while ( $noError ) {

    eval {
        my $filename = $fp . '/xx___FILLER____' . $nf++ . '.txt';
        push @filesWritten, $filename;
        
        open F, ">$filename" or die "Disk Full";
        print F substr( $randomDataCache, rand( $randomDataCacheLength
+ ) );
        close F;
        
        if ( $nf % 50 == 0 ) {
            print "Writing ${nf}th entry\n";
        }
        
    };
    
    if ($@) { print "$@\n"; $noError = 0; };
}


print "Now removing random data...\n";
map {unlink $_; } @filesWritten;



sub load_rdc {
    my $c_max = shift;
    my $s = "";
    for ( my $c = 0; $c < $c_max; $c++ ) {
        $s .= chr rand( 20 ) + 65;
    }
    return $s;
}

[download]
To have a rough idea of the time it takes, this thing filled up circa 500 mb of empty space on my Pentium II - 450 (IDE) I'm using now in say 4-5 minutes and created 18,700 files.

I'd launch it repeatedly in order to play it extra safe.

In reply to Cleaning up your hard disk by l3nz

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