Using kill to display dd progress

How long has that dd process been running for now? Is it even doing anything? How long is it going to take?

If you want dd to give you a progress update, then find out the process ID (PID) and then send the USR1 signal to it with

kill -USR1

And dd will then print out the same records in/out, bytes copied, time taken and overall speed to STDERR as it would when it finishes.

It doesn’t matter if you are re-directing STDOUT (such as to pipe the data stream to another machine via netcat or even compressing it with gzip) but make sure that you aren’t sending STDERR anywhere such as /dev/null

Make sure you specify the “-USR1” argument to kill as you don’t want to send SIGTERM to dd by mistake!
By default, kill will send SIGTERM (or SIGKILL if you use kill -9) to the specified process, but using “-USR1” you are telling kill to send a different signal, in this case one that causes dd to print the progress summary and so you aren’t actually going to “kill” the process.

You can even use have the progress refresh every few seconds with a command such as

watch -n 10 kill -USR1 $PID

Just replace $PID with the PID of the running dd process (or set the PID environment variable to the process ID).
If dd was the last command you ran, then you can get the PID with the special $! variable, otherwise you’ll have to use ps to find the PID.