Re: Help Creating A Bootable USB Disk

[tom r lopes <tomrlopes@gmail.com>]

On Sun, Aug 2, 2020 at 3:21 AM Michael Paoli <Michael.Paoli@cal.berkeley.edu> wrote:

> From: "'Christian Peeples' via BerkeleyLUG" <berkeleylug@googlegroups.com>
> Subject: Help Creating A Bootable USB Disk
> Date: Sun, 2 Aug 2020 08:24:07 +0000 (UTC)

So, now just dd to write the USB device:
# dd if=ubuntu-20.04-desktop-amd64.iso obs=4194304 of=/dev/sdb

I didn't know about the "obs" option. I've always used "bs" 

So reading the manpage I see obs is the blocksize for writing (output) 

ibs for reading (input) and bs to specify both.  I would have thought 

making the read and write block size the same is best.  

Also you can abbreviate 4194304 by 4M (so obs=4M) 

And I like to add "status=progress" because if your USB doesn't have 

any lights it is hard to know if anything is happening.  

I have been also doing "conv=sync"  Because I am just copying something 

I read somewhere.  I had thought it was like doing "sync" command after dd 

is done.  But NO!! I should check the manpages more often.  "conv=sync" 

pads the output block with zeros.  

Why would you want to do that?  

https://askubuntu.com/questions/706670/why-is-the-sync-option-used-with-the-dd-command

Second answer by Mark Plotnick

I think what I want is "oflag=sync"  

Thomas

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