Computers get replaced or upgraded, this is a fact of business and personal use. Whether the old computer is recycled, or disposed of, it is important to securely delete all information off it. Personal information, passwords, email, and documents may be on the old systems hard drive. Not securely deleting this information could lead to fraud, identity theft or sensitive information being revealed.

Normally when you delete a file from a computer it is not really removed. The information in the deleted file can be recovered. To securely erase information you must repeatedly write over every location of information on the hard drive.

This document will show you how to use a free tool to securely delete all information on a computer. This will prevent someone from recovering the computer and finding confidential information

The following procedure assumes an operational computer with a CDROM drive and a single disk drive. A Knoppix CD is required. Clearfield Computing customers may request a free Knoppix CD from us through the contact page.

Insert the Knoppix CD in the CDROM drive and turn the computer on. If the computer boots to Windows then you need to adjust the boot order in the BIOS. Shutdown Windows and reboot into the BIOS to change the first boot device to the CDROM.

When Knoppix starts it displays a splash screen with a boot prompt as listed below. At the prompt type "knoppix 2" to start in text mode. Text mode is a much faster way to perform this procedure than to start in graphics mode.

Press keys F2 or F3 for help and boot options.
KNOPPIX V3.7             http://www.knoppix.de/        RELEASE 2004-12-08

boot: knoppix 2 

It is possible on older computers to get a warning message about the video mode such as shown next. Just press the space bar to continue as Knoppix will usually figure out what to do.

You passed an undefined mode number.
Press  to see video modes available,  to continue or wait 30 secs

After going through the boot process you will be at a command prompt. Type the command listed below to wipe the disk:

root@tty1[/]# wipe -fq /dev/hda

The wipe utility will overwrite all data on the hard disk in quick mode. This mode is four passes and should be thorough enough for the ordinary business or home user. The process will take anywhere from one to four or more hours depending on the size of the hard disk and the speed of the computer.

When completed the utility will report its progress as listed below.

1 file wiped and 0 special files ignored in 0 directories, 0 symlinks removed 
but not followed, 0 errors occured.
root@tty1[/]#

Type the command: halt and the CD will be ejected and the computer will shutdown.

All information has now been removed from the disk drive and it is safe to reuse or recycle this computer.

Frequently Asked Questions

How do you know this method actually works?

The wipe utility included with Knoppix is designed to write a data pattern that prevents data recovery. The utility is based on the document Secure Deletion of Data from Magnetic and Solid-State Memory

Can I use my computers reinstall disk and wipe the hard disk that way?

Yes this method can be used but it will not securely delete the old information. A determined individual can still recover old data from the hard drive.

My old computer died and I replaced it, how can I remove the old data?

The simple solution is to remove the old disk drive and attach it to another computer. The above directions should not be followed in that case. Contact us if you need help.

My old computers hard drive failed. How can I be sure the data is eliminated on the old drive?

The first step would be to run the old hard drive manufacturers disk testing software. This may return the drive to a functional state. After that is done use Knoppix to run the wipe utility.