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I was trying to create bootable USB of Ubuntu 17.04. First, I erased everything from the pen drive and then started to copy using sudo dd if=path_to_ubuntu_image of=/dev/rdisk2 but it is taking around 5 hrs to complete the process. I read previous answers about speeding up it using rdisk instead of disk but I was initially using that only. There was to use bs but I have doubt will it bring some change in the bootable image while copying ? Please help.
Size of Ubuntu - 1.63GB
I am using the latest version of macOS High Sierra.

Link of webpage whom steps I was following - http://courses.cms.caltech.edu/cs171/materials/pdfs/How_to_Dual-Boot_OSX_and_Ubuntu.pdf

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  • Use a multiple of the page size of the system as the block size. – Ignacio Vazquez-Abrams Dec 02 '17 at 21:05
  • Related: [Is there a way to determine the optimal value for the bs parameter to dd](https://unix.stackexchange.com/questions/9432/is-there-a-way-to-determine-the-optimal-value-for-the-bs-parameter-to-dd) – Mark Plotnick Dec 03 '17 at 06:50
  • According to my experience, `bs=4096` is a good option. See this link, [My standard dd block size is bs=4096](https://askubuntu.com/questions/931581/flashing-ubuntu-iso-to-usb-stick-with-dd/931588#931588) – sudodus Jun 25 '18 at 06:09

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The default block size is only 512 bytes, which significantly cripples the transfer rate. You should use a block size that is a much, much larger.

OSX Daily has step by step instructions, they suggest 1 MB, but you might want to try even larger.

sudo dd if=/path/image.iso of=/dev/r(IDENTIFIER) bs=1m
vartec
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