I was imaging a (non-failed) internal drive to an external USB 3.0 hard drive using ddrescue -d -v /dev/sda imagefile mapfile
I know that if I abort this with Ctrl-C I can resume where I left off by re-running the command with no problem since the program has a chance to complete pending writes, etc., before stopping. But what if there is an abrupt power-off with no warning (no hibernation, no suspend, just instant loss of power to the computer and hence the external drive too)? No chance to complete cached writes, certainly not to close file handles, much less unmount the drive. I don't even know what the drive does in such cases with its internally cached but unwritten data. Since it was a 12 hour process for a 2 TB drive that was about 76% through, I didn't want to restart it from scratch. Does ddrescue guarantee non-corruption in these cases if I just restart it? Would it have made a difference if I hadn't used the -d option for direct writes to the hard drive? In this case I decided to use the mapfile.bak file the second time around, since it had a 2 minutes earlier last-modified time than mapfile, so it was cheap insurance, but was even that necessary? Shahrukh