User:Filam/Block size

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Template:Wikipedia If you have a Advanced Format hard drive it is recommended that you specify a block size larger than the default 512 bytes. To speed up the overwriting process choose a block size matching your drive's physical geometry by appending the block size option to the dd command (i.e. bs=4096).

To quickly find the block size of the device issue the following command:

# dumpe2fs -h /dev/sdX | grep 'Block size:'

For more information read How to Find the Block Size on The Linux Information Project and the Block size section in the core GNU utilites manual.


This page lists examples of the dd block size flag (i.e. bs=) on English language pages. The following examples all come from the first page of a search for "bs=".

User-mode Linux

dd if=/dev/zero of=rootfs bs=1MB count=1000

Remote Arch Linux Install

# dd if=/dev/zero of=/swapfile bs=1024 count=512288

USB Installation Media

# dd count=1 bs=512 if=/dev/zero of=/dev/sdx

Windows and Arch Dual Boot

dd if=$my_boot_part of=/media/win/linux.bin bs=512 count=1

Dm-crypt with LUKS

# dd if=/dev/urandom of=mykeyfile bs=512 count=4
# dd if=/dev/urandom of=secretkey bs=512 count=4


$ dd if=/dev/zero of=image.img bs=1G count=0 seek=[NUMBER_OF_GB]

JFS Filesystem

dd bs=4k if=/dev/hdc1 of=/dev/hdj1

Installing ArchPPC on a PS3

$ dd if=/dev/zero of=/arch/swapfile bs=1024 count=<# of KiB>

See also