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dd is an underrated tool. What it lacks in user interface it makes up for with its swiss-army-knife number of purposes; from testing, to secure wiping, to backup and restore. But that user interface... it is bleak.

zcat bcmImage.gz | dd of=/dev/sdd bs=512

Text 1: Uncompress the image from the file bcmImage.gz and write it to the system's fourth physical volume.

So dd is running, doing something, maybe. The only way you can really tell is to look at the harddrive lights or inspect some performance counters - somebody is using those drives. But dd has more user interface than it lets on; send it the signal USR1 and it will report its status. You can send as many USR1 signals as you like, it will report every time; it does not interrupt the operation.

awilliam@linux-86wr:~> dd if=/dev/urandom of=/dev/null bs=1024

Text 2: Start a dd operation.

awilliam@linux-86wr:~> sudo killall -USR1 dd

Text 3: Send dd a USR1 signal; from another tty (obviously).

awilliam@linux-86wr:~> dd if=/dev/urandom of=/dev/null bs=1024
78883+0 records in
78882+0 records out
80775168 bytes (81 MB) copied, 6.262 s, 12.9 MB/s

Text 4: dd reports without interrupting what it is doing.


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