How can I securely erase a hard drive?

Question

I'm planning on selling a USB external hard drive that currently contains an old Ubuntu installation with stored passwords and banking information.

How can I securely erase the drive before selling it?

Answer 1

Securely erasing a storage device

There's a command-line utility called shred, which overwrites data in a file or a whole device with random bits, making it nearly impossible to recover.

First of all, you need to identify the name of the device.

This might be something like /dev/sdb or /dev/hdb (but not like /dev/sdb1, that's a partition). You can use sudo fdisk -l to list all connected storage devices, and find your external hard drive there.

N.B. Make sure it is the correct device, picking the wrong device will wipe it.

Unmount all currently mounted partitions on that device, if any. Then run the following, replacing /dev/sdX with the name of your device:

sudo shred -v /dev/sdX

This will overwrite all the blocks on the device with random data three times, the -v flag is for verbose and will print the current progress.

You can add the option -nN to only do this N times, to save time on large capacity devices. This might take a while, depending on the size of your external hard drive (I think it takes twenty minutes or so for my 4 GB flash drive).

You can also set all bits to zero after the last iteration by adding the option -z, I prefer to do this.

sudo shred -v -n1 -z /dev/sdX

After this, you would have to repartition the device. The easiest way is to install GParted and use it:

sudo apt-get install gparted
gksu gparted

Choose your device in the upper-right corner list. Then select Device -> Create partition table to create a partition table on the device.

Then add a single partition that uses all of the unallocated space on the device, choosing fat32 as the file system. Apply the changes by click the Apply button (the green checkmark) in the toolbar.

Tips

• Read the manpage for shred online or by typing man shred in the terminal.
• Beware that some parts of your disk will not be erased - use the drive firmware "SECURE ERASE" command, such as via hdparm, to properly clean off a disk.

Answer 2

Just 'zero' it using the dd tool:

1. Start the Disk Utility via System > Administration > Disk Utility
2. Find your disk in the left panel, select it, and on the right find the device path (eg. /dev/sdX )
3. Run the following command from a terminal (Applications > Accessories > Terminal):
   
   sudo dd if=/dev/zero of=/dev/sdX bs=1M
   
   Make sure you use the right device path and not just copy this line!

This will overwrite the whole disk with zeros and is considerably faster than generating gigabytes of random data. Like all the other tools this won't take care of blocks that were mapped out for whatever reason (write errors, reserved, etc.), but it's highly unlikely your buyer will have the tools and the knowledge to recover anything from those blocks.

PS: Before you Bruce Schneier fanboys downvote me: I want proof that it's possible to recover data from a non-ancient rotational hard drive that has been overwritten with zeros. Don't even think about commenting otherwise! :P

Answer 3

I generally use a destructive read-write test using badblocks -w. The two major advantages are:

• it's part of the base system and almost every rescue system, so it is available e.g. from the rescue shell of the Ubuntu installer
• you get a report at the end whether there are bad blocks on the disk

Note that if the report indicates a problem, I'd no longer sell the disk as it is likely to fail soon.

Also Note: The -w does a 4-pass destructive write test by default.

Use write-mode test. With this option, badblocks scans for bad blocks by writing some patterns (0xaa, 0x55, 0xff, 0x00) on every block of the device, reading every block and comparing the contents.

Usage example (if your disk is sdd):

sudo badblocks -wsv /dev/sdd

(added sv for progress bar + verbose)

For a much faster wipe, add the -t option and do a single pass of zeros like so:

sudo badblocks -wsv -t 0x00 /dev/sdd

Answer 4

Have a look at this definitive question on Security Stack Exchange

How can I reliably erase all information on a hard drive

This discusses various secure deletion options, along with physical destruction and wiping so you can decide which option may be your best bet.

Remember though that the current recovery status for different storage is as follows:

• Very old hard drives: there were gaps between tracks so you could potentially pick up bleed into these gaps (if you had a scanning electron microscope handy). Overwriting multiple times was potentially useful.
• New hard drives: no technology currently exists that can read after even one overwrite.
• Solid state hard drives: wear levelling means you cannot overwrite securely. Instead you either encrypt the entire volume and dispose of the key to wipe, or you destroy the device.

Answer 5

Best is to use the secure erase function of ATA drives. Secure erase erases the drive at firmware level. Can't get more secure.

First check if secure erase is supported:

sudo hdparm -I /dev/sdX | grep -i security

(replace sdX with sda/sdb/sdc, whatever your disk is).

If you see no output, just use dd:

sudo dd if=/dev/zero of=/dev/sdX bs=1M

If you see output, check if the device is not frozen:

sudo hdparm -I /dev/sdX | grep -i frozen

If it is frozen, see How to unfreeze drive in Linux? Otherwise if you see not frozen, set password to "Eins":

sudo hdparm --user-master u --security-set-pass Eins /dev/sdX

Optional: you might want to know how how long this will take:

sudo hdparm -I /dev/sdX | awk '/for SECURITY ERASE UNIT/'

Then execute the erase:

sudo hdparm --user-master u --security-erase Eins /dev/sdX

Then wait. Apparently for a 1TB disk this might take 3 hours or more.

There's a nice script which automated these steps.

Answer 6

Now, Disks (gnome-disks) tool has ATA Secure Erase. You may use it to erase your hard drive. Same option explained in this answer using the command-line tool hdparm.

---

WARNING!

Please, review disclaimer and warning notes at https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase (Thanks to @colan to bring this up)

Also comments below. Some hardware may break.

---

1. Open Disks tool → Choose the target disk
2. From menu: Format Disk...
3. Select from drop box, Erase: ATA Enhanced Secure Erase ( if offered for the drive you selected ). Alternatively you can select Write zeros (slow) which can reasonably be considered to be secure.
4. Format

Answer 7

• You need to create a loopback device which runs /dev/random over the entire contents of the drive.

• That'll fill the entire drive with almost completely random data.Then you can set all bits back to 0 with dd.

• Actually, dd should be able to randomize all of the information.

• You said that you have stored banking information on your harddisk.So i would suggest you to run any one of the following command from a live cd (where hdX is your harddrive).

  dd if=/dev/zero of=/dev/hdX

  dd if=/dev/random of=/dev/hdX

  dd if=/dev/urandom of=/dev/hdX

• How ever it will take a very long time based on your harddisk size.

For your information:

See the following links,

• Tools to delete files securely in ubuntu Linux
• Use an Ubuntu Live CD to Securely Wipe Your PC’s Hard Drive

Note:

• Random uses random bits and zero uses 0 bits.
• Urandom is a semi-random version of random.

Answer 8

you can use wipe

Installation

sudo apt-get install wipe

You can use that software or use the following command:

shred -vfz -n ? (drive)

Were the "?" is, put the number of times you wan to shred the drive, then for were "(drive)" is, put the drive that you want to shred. Once your done, do whatever you want with it. I think that this method is more effective since you can control what is done to your drive and have immediate results.

Links

1. http://wipe.sourceforge.net/
2. http://www.howtogeek.com/howto/15037/use-an-ubuntu-live-cd-to-securely-wipe-your-pcs-hard-drive/
3. http://ubuntuforums.org/showthread.php?t=817882

Answer 9

One more advantage of shred over dd in this scenario: I have a faulty disk that I need to return to the vendor for an exchange.

dd halts at the first bad block, and fails to clobber the rest (unless I painfully use skip=... to jump ahead each time it stops).

shred ignores write errors and happily continues in this case.

Answer 10

You can use DBAN. Wikipedia:

Darik's Boot and Nuke (commonly known as DBAN) [...] is designed to securely erase a hard disk until data is permanently removed and no longer recoverable, which is achieved by overwriting the data with random numbers generated by Mersenne twister or ISAAC (a PRNG). The Gutmann method, Quick Erase, DoD Short (3 passes), and DOD 5220.22-M (7 passes) are also included as options to handle Data remanence.

DBAN can be booted from a floppy disk, CD, DVD, or USB flash drive and it is based on Linux. It supports PATA (IDE), SCSI and SATA hard drives. DBAN can be configured to automatically wipe every hard disk that it sees on a system, making it very useful for unattended data destruction scenarios. DBAN exists for Intel x86 and PowerPC systems.

DBAN, like other methods of data erasure, is suitable for use prior to computer recycling for personal or commercial situations, such as donating or selling a computer[2]. In the case of malware infection, DBAN can be used before returning a disk to production.

Answer 11

Use lsblk to get the disk name.

CAUTION: Don't zero-fill an SSD, ever. Find more details here.

In case of HDD, you can use the following commands.

sudo dd if=/dev/zero of=/dev/sdX bs=4096 count=2013054 status=progress

or,

sudo dd if=/dev/urandom of=/dev/sdX bs=4096 count=2013054 status=progress

or,

sudo dd if=/dev/random of=/dev/sdX bs=4096 count=2013054 status=progress

Replace X with appropriate letter.

Please note that you need to use count= otherwise you will get dd: error writing '/dev/sdX': No space left on device

To calculate count=, you can use the following command.

echo $(($(df --output=size -B1 /dev/sda | tail -1)/4096))

Please replace 4096 with your bs= value.

For NVMe or SATA SSD, read on. From now on the following CAUTION will be applicable.

CAUTION: Do not proceed with this if the target drive is not connected directly to a SATA/NVMe interface. Issuing the Secure Erase/Format/Sanitize command on a drive connected via USB or a SAS/RAID card could potentially brick the drive!

For SATA SSD drive check SATA SSD.

For NVMe drive check NVMe Drive.

Answer 12

Go root and

dd if=/dev/random of=/dev/(your usb drive device here); dd if=/dev/zero of=/dev/(your usb drive device here)

Be certain you've got the right drive!

Answer 13

DBAN is an open source Boot CD to wipe the hard disk.

Down load from

http://www.dban.org/download

burn it and boot the machine from CD, that's all.

Answer 14

Easiest way to do that is use :

sudo shred -fv /dev/xxx

where xxx is device, to ensure what device you have, type :

sudo fdisk -l

The device are indicated after disk word and to the colon char :, like this :

Disk /dev/sde: 500.1 GB etc...

Don't mount file systems of your disk you want wipe etc. Shred will do what you want in part of time. -z option is for last run with 0 to hide wipe and is not necessary to wipe data.

Best way is to use dd like wrote previous users:

sudo dd if=/dev/urandom of=/dev/xxx bs=1M

use urandom device as it is more modern and better way to obtain random pattern.

Other tools at this moment can be older and by less people develop. Shred is in core application of Linux.

Look at this example: wipe 2009 http://lambda-diode.com/software/wipe/. But it is known app. It is possible to use bleachbit but as I tried it took long time.

Answer 15

If the dd cmd is not working, you can use the redirection method to wipe out the data.

Like,

cat /dev/urandom > /dev/sd**a**   # depends on your hdd location 

or

alternatively you can use cp (copy cmd) to overwrite the previous data.

cp /dev/urandom /dev/sd**a**      # depends on your hdd location 

Answer 16

Use nwipe, it's command line or ncurses GUI. Has multiple wipe methods. Can wipe many devices simultaneously. It's the more up to date version of DBAN and is currently maintained. Nwipe can be found in most Linux distros and is available as a bootable USB version called Shredos

Nwipe https://github.com/martijnvanbrummelen/nwipe

Shredos https://github.com/PartialVolume/shredos.2020.02

Answer 17

You can use pv to zero-fill it and you'll even get a nice progress bar:

pv < /dev/zero > /dev/sdX

where sdX is the device of the drive to delete; you can get that from this command:

lsblk

Taken from pv(1)

You can also one-fill it with pv:

tr '\0' '\377' < /dev/zero | pv > /dev/sdX

Partially taken from monkeybus's answer

Answer 18

Those recommending to use shred are giving bad advice. Shred's own man page says it's effectively useless on journaled filesystems, which Ubuntu is almost guaranteed to be using if you don't change its filesystem defaults (ext3 and ext4 are journaled. As is resierfs and Reiser4 as well as many MANY other common Linux filesystems.).

Not to mention shred is completely useless for completely blanking or randomizing a disk, as it only works on individual files or sets of files (On the filesystem level, not a raw data level.). If you want to securely wipe a disk, you gotta use dd on the drive's main device node (For example: /dev/sdc instead of /dev/sdc1) while nothing is mounted on it.

It WILL take a while, but unlike shred it will completely and IRREVERSIBLY wipe a hard disk from MBR to final sector. Also, BIG WARNING on dd, make sure you are using it on the correct device or you'll at least PARTIALLY wipe the wrong disk. This could be disastrous if you accidentally use dd on a system drive, which will not only make it unbootable, but may irreversibly corrupt any given partition on the drive. This has given it the nickname "disk destroyer."

Shred is NOT a reliable tool for securely wiping a drive. If you're selling or giving your computer away the CORRECT way to empty the drive is to zero or randomize it with dd and never, ever use shred, as filesystem journals will effectively restore shredded files with no effort at all.