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What does bs=8M in the dd command do while creating a Fedora live USB?

asked 2013-06-13 23:47:58 -0500

k1monfared gravatar image

updated 2013-06-14 01:11:38 -0500

FranciscoD_ gravatar image

I'm experiencing a lot of un-stability problems in ubuntu, so I decided to immigrate to fedora. Unfortunately ubuntu startup disk creator application doesn't support fedora iso files. In the fedora project wiki page it is suggested to use this command in ubuntu to create a fedora live usb stick:

sudo dd if=/Users/me/Downloads/Fedora-17-x86_64-DVD.iso of=/dev/sdX bs=8M

My question is what does the last bit of the command do, i.e. bs=8M. Is it the amount of space to save files and settings in live fedora?

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answered 2013-06-14 00:32:04 -0500

wraeth gravatar image

updated 2013-06-14 00:33:31 -0500


The bs=8M relates to the size of each block written to the disk - for this, it will read/write 8MB blocks at a time. It doesn't have any significant impact on performing this sort of operation, other than to (hopefully) make the process work a little quicker.

You can read the man page for more information (man dd).


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answered 2013-06-14 00:31:10 -0500

skytux gravatar image

Please don't forget to read the man pages:

$ man dd (*)


bs=BYTES -> force ibs=BYTES and obs=BYTES

ibs=BYTES -> read BYTES bytes at a time

obs=BYTES -> write BYTES bytes at a time

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Asked: 2013-06-13 23:47:58 -0500

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Last updated: Jun 14 '13