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Old 03-15-2009, 06:08 AM   #1
skubik
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dd block size limit on ext3?


I'm wanting to setup an encrypted iso file for sensitive information. There is a lot I want to 'backup' onto this encrypted iso- about 4.2G worth. I have done this procedure before, but not with such large files.

First I'm using 'dd' to create the iso image file, but it's failing when I give it the size of file I want it:

> dd if=/dev/urandom of=ISO0.iso bs=4.2G count=1
dd: invalid number '4.2G'

I'm attempting to create ISO0.iso on an ext3 filesystem, so it can't be a file-size limitation. I have files much larger than 4.2G on the same drive- same directory even! This makes no sense. Can someone explain why this might not be working? I'm using dd version 6.9

Thanks,

- skubik
 
Old 03-15-2009, 10:56 AM   #2
unSpawn
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Try using args that makes sense like "bs=1MB count=4200"?
 
Old 03-15-2009, 12:10 PM   #3
mangezoutianya
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Yes,the value of "bs" is supposed to be an integer.
 
Old 03-15-2009, 02:01 PM   #4
skubik
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Thanks. I thought I read somewhere online to use a file with a block size as large as the size of the filesystem you want- in this case 4.2G. But when I went back to find it, it doesn't seem to appear anywhere. Still- I have been able to use "bs=1G count=1" just fine, but when I try and go bigger than 1G, it fails. I kinda get why that might be. Oh well- I'll adjust count accordingly.
 
  


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