The sys admin's daily grind: ddrescue and DDRescue-GUI
Recovery Needed
Sometimes even sys admin Charly doesn't have a backup at hand; or, maybe it's ruined because the removed disk had corrupt data. Here, he offers some advice on how to handle the situation.
Krrr, krrr …! At least things are clear-cut when a hard disk gives up the ghost: You toss the offending disk, get a new one, and put the backup on it. However, those undead data media – that trick people into continuing working on them with no idea of the potential impact – are a real pain.
I recently determined that an SDHC card in my camera saves one out of 20 images (on average) as a colorful mess of pixels. I do know that memory cards give up the ghost sooner or later. However, I didn't realize that my camera could save to two cards simultaneously – a feature I stupidly didn't use. But, I'm all the wiser now.
What if really important data is stored on a haywire device that you just can't get rid of? This is where ddrescue [1] comes in. The tool is already quite ancient, but its developers look after it untiringly and adapt it to new types of data media. (It should not be confused with the even older dd_rescue.) Ddrescue is officially named GNU ddrescue; the packages on Debian and derivatives are therefore dubbed gddrescue.
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