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Old 04-12-2014, 02:04 PM   #1
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/dev/null or /dev/zero?

What is the difference between dd if=/dev/null of=/dev/HDD or HDD parititon and dd if=/dev/zero of=/dev/HDD or HDD parititon? English please, and which one should I use to my sda5 partition?
Thank you in advance
Old 04-12-2014, 02:44 PM   #2
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Hi there,

Originally Posted by funkypunkypinkypow View Post
What is the difference between dd if=/dev/null of=/dev/HDD or HDD parititon and dd if=/dev/zero of=/dev/HDD or HDD parititon?
briefly put, /dev/null yields no input (just an eof() condition), while /dev/zero produces an endless stream of NUL bytes as input. When used as output, both ignore any data being sent to them.

So if you use /dev/null as an input for dd, the operation will stop before it has really started, effectively leaving the hard disk unchanged, while /dev/zero being used as an input really results in your hard disk being erased sector by sector, byte by byte.

Honestly, I also used to mix up /dev/null and /dev/zero for quite some time.

[X] Doc CPU

Last edited by Doc CPU; 04-12-2014 at 03:30 PM. Reason: Fixed a typo.
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Old 04-12-2014, 03:01 PM   #3
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You send output you don't want to /dev/null. You use /dev/zero to output zeros to a file or device.


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