The sys admin's daily grind: ddrescue and DDRescue-GUI

Recovery Needed

Article from Issue 182/2016

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.

The tool is included with many popular distributions. The first two letters subtly indicate a relationship with dd, and ddrescue actually generates a data medium's or partition's image. Unlike dd, however, it can't be stopped by read errors; instead, it stubbornly saves everything that it can get its teeth into.

Two-Speed Transmission

Administrators usually use ddrescue in two phases. The first phase involves creating an image with all the data that can be accurately read. In the following example, /dev/sdd1 is a partition with read errors on a USB flash drive:

sudo ddrescue -n /dev/sdd1 /home/charly/stick.img logfile.log

The second, more time-consuming phase involves using the tool to sort through the faulty blocks and save as much data from them as possible. The command is just the same as before, except you leave out the -n parameter. In the wake of ddrescue, there is still an armada of other parameters that control the tool's behavior.

There is also a GUI [2] that you can use to make some quick, useful default settings. I installed it quickly on my test Ubuntu using these three steps:

sudo add-apt-repository ppa:hamishmb/myppa
sudo apt-get update
sudo apt-get install -fym ddrescue-gui

As Figure 1 shows, the interface is businesslike and functional. The GUI sets the important parameters, but not all of them by far. Although I hope no one will need to use ddrescue permanently, the GUI is nevertheless a real help.

Figure 1: The genuinely helpful front end for ddrescue is DDRescue-GUI, which graphically implements the important parameters.

The Author

Charly Kühnast is a Unix operating system administrator at the Data Center in Moers, Germany. His tasks include firewall and DMZ security and availability. He divides his leisure time into hot, wet, and eastern sectors, where he enjoys cooking, freshwater aquariums, and learning Japanese, respectively.

Buy this article as PDF

Express-Checkout as PDF
Price $2.95
(incl. VAT)

Buy Linux Magazine

Get it on Google Play

US / Canada

Get it on Google Play

UK / Australia

Related content

  • Data Rescue

    Armed with just standard Linux tools, users can recover files, resurrect partitions, and rescue damaged media.

  • Parted Magic 2.0 with New Visparted Tool

    The Parted Magic Linux Live System gives users the ability to manipulate hard disk partitions in various formats. Version 2.0 is the first to rely on the Visparted GUI tool .

  • Tool Tips

    Tools tested: MenuMaker, CLOC, ddrescueview, Hiawatha,, and XDM.

  • Partition Backup

    A partition backup offers several advantages over legacy, file-based backup alternatives, and using a backup server adds even more convenience. We’ll show you some free tools for partition backup over the network.

  • Charly’s Column: Btrfs

    Btrfs might not be complete, but conceptually, it combines so many useful filesystem functions that Charly couldn’t wait to play around with it.

comments powered by Disqus
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters

Support Our Work

Linux Magazine content is made possible with support from readers like you. Please consider contributing when you've found an article to be beneficial.