On Mon, Jun 24, 2013 at 09:55:46AM -0600, paul condon wrote: > I have two 3TB Seagate external HDs. They were purchased from > different stores at slightly different times earlier this year, here > in Colorado. I want them to have ext4 file systems on them, > excepting if someone on this list can give a reason otherwise. I > have googled and gotten a lot of hits, which indicate to me that > this is a well known problem. Unfortunately, I have difficulty > following the instructions, and all my efforts have not reached a > successful conclusion. Now with further trys, it seems to me that > stuff has been written onto the drives that needs to be wiped off > because I get messages that from the disk utility in xfce4 that it > won't overwrite a disk with data on it. > > So I want to use dd to wipe a complete drive. > For this I have found the following: > # dd if=/dev/zero of=/dev/sdg bs=1M > In the above, I have already changed the HD device to sdg (from > sda), but I wonder about bs=1M. Could the process go faster with a > larger block size?
Possibly. There exists a tool (https://github.com/sampablokuper/dd-opt) to help you find the fastest blocksize > What are the criteria for choosing a value for > bs? And, how long should a 3T wipe take to complete? The job has > been running for about 12 hours. Would it go faster with a different > bs? Faster enough to make the waste of 12hrs running worthwhile? Is > there some way to invoke an 'progress indicator' for dd? You can send SIGUSR1 to a running dd and it will print current statistics to STDERR. term1$ pkill -USR1 dd term2$ dd if=/dev/zero ... 0+14 records in 0+14 records out 204 bytes (204 B) copied, 24.92 seconds, 0.0 kB/s Another alternative would be to run the data through pv: $ dd if=/dev/zero | pv | dd of=/dev/sdg bs=1M > And, in > general, is there a better way? You could try just overwriting the first few megabytes of the partition. If a mkfs is checking to see if there's already a filesystem in place, chances are it won't look VERY hard. Wiping out the start of the disk should make it look 'clean enough'. So add "count=N" (where N is a small number) to your dd command line.
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