feat(blog): Add ddrescue article

content/blog/2024-12-11-ddrescue.md

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+title = "Introduction to ddrescue"
+date = "2024-12-11"
+updated = "2024-12-11"
+[extra]
+authors = ["Ydreniv"]
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+
+Let’s suppose one of your friends come to you with a computer issue.
+They’ve got a failing hard drive, and want to recover the data stored on their
+device.
+They are quite worried, as they have important files on it, and it’s their
+only copy.
+Of course, this would never happen to you, because you keep multiple encrypted
+backups of all your data, in multiple place.
+Only a worldwide apocalypse would get you a dataloss.
+So this definitely could *only* happen to a friend, or a family member, but
+not you.
+It would be preposterous to think otherwise.
+
+So anyway, you want to copy the hard-drive.
+You quickly plug it in your computer, mount it and open the file explorer.
+But the mount takes a long time, accessing the files is very slow, and copying
+them does not always work.
+Plus, the [SMART](https://wiki.archlinux.org/title/S.M.A.R.T.) statistics show
+that this drive has *issues*.
+How do you extract the important data then ?
+By the look of it, the vast majority of the drive sectors are fine, so what
+you’re looking for still exists.
+It’s merely hard to access.
+It’s only a hardware problem.
+
+If you manage to image the drive, you can then either use it as a mounted
+file, or burn it to another drive.
+You could use good old `dd`.
+Maybe this would work.
+But here, with your friend’s disk on its deathbed, you’d like a tool adapted
+for this situation.
+Here comes…
+**[ddrescue](https://www.gnu.org/software/ddrescue/)**.
+
+`ddrescue` operates on unmounted devices, and will copy a device block by
+block.
+Even better, it has error handling integrated.
+When it cannot read a block, it will either retry or pass it, depending on the
+options you’ve selected.
+And, crucially, it can store its status in a file, meaning that if you stop
+the process, you’ll be able to resume it later.
+This way, you can quickly recover all easily available blocks, while still
+retaining the ability to do several passes on the failing ones.
+
+I’m still a novice in `ddrescue`, so read the [Archlinux wiki
+page](https://wiki.archlinux.org/title/Disk_cloning#Using_ddrescue) to get
+specific instructions.
+The Archlinux wiki is overall pretty good, and is one of my main source of
+help on Linux, even with other distributions.
+In my experiment, it has been able to recover all the disk’s sectors, except
+for 47 of them.
+I let it run for at least 50 hours I guess (I haven’t counted) over multiple
+sessions.
+I could probably try to make more passes, to eventually recover the full disk,
+but I’m not sure it’s worth it (and even possible).
+
+It’s reassuring to know that I’ve now safeguarded most of the data.
+Now that I have a mostly complete image, I’ve started trying to read them.
+Unfortunately, the missing blocks do prevent me from simply mounting the
+resulting image.
+So I’ve still gotta do some work to actually get what I wanted (copying the
+files to another drive), but at least I know that the current image is safe,
+and that there shouldn’t be further data loss.
+
+So if you’re confronted with data recovery, I recommend giving `ddrescue` a
+look. It’s quite a useful tool !
+