1. When re-installing Windows XP it will try to reuse the previous installation. If the previous installation is virus ridden or damaged in some other way, you will certainly want to make sure it is completely wiped out. In this case you should zero out the entire hard drive to make sure any partition table viruses are removed. Do of course, back up your virus free data first.
2. If you want to make an exact mirror image of a partition, it's very important to zero out the partition first. The reason is that all the free space will then have zeros which will compress down to next to nothing. Refer to Disk Mirror Imaging for instructions on this procedure.
3. This is an easy way to wipe a disk or partition clean so others cannot read it.
Here are some links to ISO images of bootable CDs that you can download and burn on a CD:
You can use cdrecord to write an ISO image (.iso) to a CD.
All the keystrokes that you sould type in at the command prompt are in green.
BE SURE TO BACK UP ALL DATA THAT YOU WANT TO KEEP BEFORE ZEROING IT OUT!
As Linux boots it will display all the stuff it's setting up and configuring, unlike Windows which does most all the same stuff but hides it all.
Each Linux boot disk has a little different user interface, but they all involve the same basic steps and each one should give you enough information so you can answer the prompts (if there are any) and get to a login prompt. You will need to log in as "root" which should be indicated on the screen above the login prompt.
Every once in a while, a boot disk will not work right or hang on a certain machine. If this happens, try a different one, some disks are configured to work with a wider variety of hardware than others. Older versions of boot disks tend to work better with older hardware - but always try the latest version first.
Linux assigns names to disks and partitions in a much more logical, but different way, than windows does. Windows assigns letters to the primary partitions first and then to extended partitions. If you have a variety of primary and extended partitions, this can make for a jumbled up set of drive letters. Linux on the other hand, assigns names to each of the IDE drives connected to the mainboard as follows:
IDE0, Master: /dev/hda IDE0, Slave: /dev/hdb IDE1, Master: /dev/hdc IDE1, Slave: /dev/hdd SCSI ID0: /dev/sda SCSI ID1: /dev/sdb
Partitions are then assigned numbers in order as follows:
First primary partition of hda: /dev/hda1 Second primary partition of hda: /dev/hda2 Third primary partition of hda: /dev/hda3 Fourth primary partition of hda: /dev/hda4 First extended partition of hda: /dev/hda5
With that bit of information understood, now have a look at the drive configuration in the computer. Most bootable Linux disks keep a log of the boot messages. From the log messages, you can see what brand and size of drives are in the computer.
Use dmesg to display the boot time messages.
Here are drive info. lines extract from my boot log:
dmesg -s65536 | less
hdb: 55704096 sectors (28520 MB) w/512KiB Cache, CHS=3467/255/63, UDMA(33) hdc: 37615536 sectors (19259 MB) w/418KiB Cache, CHS=37317/16/63, UDMA(33) SCSI device sda: 17783240 512-byte hdwr sectors (9105 MB)
In the above example, I used the pager command, less (instead of more ), if you don't know how to use it, press h after having entered the above line.
After detemining which drive(s) you want to zero out, use fdisk to list the partitions on the drive(s).
fdisk -l /dev/hda Disk /dev/hda: 3227 MB, 3227148288 bytes 128 heads, 63 sectors/track, 781 cylinders Units = cylinders of 8064 * 512 = 4128768 bytes Device Boot Start End Blocks Id System /dev/hda1 * 1 9 36256+ b W95 FAT32 /dev/hda2 10 777 3096576 83 Linux /dev/hda4 778 781 16128 5 Extended /dev/hda5 778 779 8032+ 83 Linux /dev/hda6 780 781 8032+ 83 Linux
In this case, I want to zero out the win95 partition, /dev/hda1
dd if=/dev/zero of=/dev/hda1
To zero out the entire drive, use:
dd if=/dev/zero of=/dev/hda
After the dd command finishes (it can take a while), your drive or partition will be wiped cleaned and ready to use. You can restart the computer by pressing Ctrl-Alt-Del or running the reboot command.