Debian – Why did dd create a different uuid

dddebianuuid

root@debian:/home/tiger# dd  if=/dev/sda  of=/dev/sdb  bs=10240k
11447+1 records in
11447+1 records out
120034123776 bytes (120 GB) copied, 4729.59 s, 25.4 MB/s
root@debian:/home/tiger# blkid
/dev/sda1: UUID="54AF-15B1" TYPE="vfat" 
/dev/sda2: UUID="28D02E2FD02E03A2" TYPE="ntfs" 
/dev/sda5: UUID="a3464de4-5676-4ae3-b37a-a1f40708d5ec" TYPE="swap" 
/dev/sda6: UUID="8b29114c-4f89-4c96-b0c0-579ce58c7345" TYPE="ext3" 
/dev/sdb1: UUID="54AF-15B1" TYPE="vfat" 
/dev/sdb2: UUID="28D02E2FD02E03A2" TYPE="ntfs" 
/dev/sdb5: UUID="a3464de4-5676-4ae3-b37a-a1f40708d5ec" TYPE="swap" 
/dev/sdb6: UUID="d38e60d8-6bfe-49f9-a381-d89b3b9bbb7f" SEC_TYPE="ext2" TYPE="ext3"

Why doesn't /dev/sda6's uuid equal /dev/sdb6's?

Edit, answering questions from comments:

  1. sda and sdb are same size disk

  2. The output of blkid -p is:

    root@debian:/home/tiger# blkid -p /dev/sda6  
/dev/sda6: UUID="8b29114c-4f89-4c96-b0c0-579ce58c7345" VERSION="1.0" TYPE="ext3" USAGE="filesystem"

Best Answer

You didn't give the blkid -p output for the interesting partition (/dev/sdb6), but that'd almost certainly give 8b29114c-4f89-4c96-b0c0-579ce58c7345. I suspect if you tried:

blkid -c /dev/null

you'd get the output you expect—the UUIDs would match.

You're just seeing the effects of a stale cache /etc/blkid.tab and you can fix it by:

echo -n > /etc/blkid.tab
blkid

That'll empty and regenerate the cache.

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