[cs615asa] HW3 dd restore hangs

[Rob Hoffmann]

Nevermind, it was a simple matter of not waiting long enough. I forgot 
that dd will copy the empty blocks as well, so a remote transfer will 
take a long time.

On 3/16/2012 2:19 PM, Rob Hoffmann wrote:
> I'm having some trouble with restoring from a remote volume using dd. 
> I attach the ebs volume as /dev/sdf and then tar and dd the archive 
> over with obs=256k. That works okay, but when I try to restore the 
> files back using dd ibs=256k and piping it into tar, I see my all my 
> files printed via -v flag but at the end of the listing the process 
> just hangs and never finishes until I kill it.
>
> Example output:
>
> rob at heavy:~/programs/misc/sh$ tar cvf - . | ssh -i 
> /home/rob/id_rsa-gsg-keypair 
> root at ec2-107-21-185-218.compute-1.amazonaws.com 'dd of=/dev/sdf obs=256k'
> ./
> ./ec2-backup
> ./test/
> ./ec2-start-instance
> 40+0 records in
> 0+1 records out
> 20480 bytes (20 kB) copied, 0.067686 s, 303 kB/s
> rob at heavy:~/programs/misc/sh$ ssh 
> root at ec2-107-21-185-218.compute-1.amazonaws.com -i 
> /home/rob/id_rsa-gsg-keypair 'dd if=/dev/sdf ibs=256k' | tar tvf -
> drwxr-xr-x rob/rob           0 2012-03-16 13:45 ./
> -rw-r--r-- rob/rob        6462 2012-03-16 13:40 ./ec2-backup
> drwxr-xr-x rob/rob           0 2012-03-16 13:45 ./test/
> -rwxr-xr-x rob/rob        1198 2012-03-15 18:50 ./ec2-start-instance
> ^Crob at heavy:~/programs/misc/sh$
>
> The files are there and will transfer over if I use -x flag on tar, 
> but dd will not end until I hit ctrl+C. If I remove the pipe to tar in 
> the second command the content of the files will print to screen but 
> it will still hang, so I know dd is the issue, not tar.
>
> If I use of=/dev/st0 (SCSI tape device) instead of sdf that will 
> backup & restore fine, but I can't mount the ebs volume under that 
> name. Has anyone else had this problem?
>
> -Rob
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