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I needed to clone a hard drive, so I bought the exact same model that I have and stuck it into the computer. I put Ubuntu live on a flash drive and boot up from it. I check with sudo fdisk -l that I really want to clone sda to sdb. Then I type

sudo dd if=/dev/sda of=/dev/sdb bs=1M

and press enter. This is first time I do it. I knew there's no progress bar or anything but I expected hard drives to at least make some noise to let me know they went on cloning.

Nothing. After about 10 minutes screen goes dark, I wiggle the mouse around and it's back. Later it goes dark again. This time neither moving mouse around nor hitting space bar help. The screen is dark.

Any way to bring it back? If I restart Ubuntu while dd-ing, would this damage either of hard drives? I've googled this and has only found that Ubuntu live doesn't have a standby mode. Pretty confusing.

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Are you sure it is even running at that point? Has the system had thermal and halted? –  Tim Dec 6 '11 at 21:58
On another note, grab pipeviewer, then you can run your DD like so dd if=$INDEV | pv -s ``blockdev --getsize $INDEV`` | dd of=$OUTDEV to get a progress bar. –  Tim Dec 6 '11 at 21:59
The fan is still spinning and hard drives do make some noises time to time. However, the keyboard doesn't seem to be getting any juice - when I press caps lock, the light doesn't come on. –  dfo Dec 6 '11 at 22:09
Thanks for the pipeviewer tip. I'll use it once I figure out if I can reboot... –  dfo Dec 6 '11 at 22:09
Simply power cycling should not physically damage either of the drives. Since sda shouldn't be mounted, there should be no chance of any corruption on sda. SDB may not have a complete image, and so you should probably treat was on it as junk. –  Zoredache Dec 6 '11 at 22:16

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