Chapter 2. Data Recovery Concepts

Abstract

In order to be able to use any data recovery tools, you need to understand some of the concepts behind data recovery. This chapter will explain the basics, and it will also show you how to get help when you're using the GUI. You can safely skip this chapter if you already understand the concepts, because I've gone into fairly basic detail here.

Table of Contents

Device Names
Partitions and File Systems
"Mounting" and "Unmounting" Devices
Bad Sectors
Data Corruption
"Disk"
Formatting
Deleting and Undeleting
Image Files
The Disk Info Window

Device Names

Device names are a bit of a weird concept to a lot of people, particularly those who use Windows, where drive letters are used instead, like C:, D: and so on. On Linux and macOS, however, devices (like hard drives, USB drives, DVD drives) have names. These names are used to access the drives, so for example, to read directly from the DVD drive, you might read from a device called "/dev/sr0" (Linux), or "/dev/disk1" (macOS), which you can think of as being similar to the D: drive in Windows.

[Tip]Tip

Please note that DDRescue-GUI also the Linux device name conventions on Windows! You can relate the Linux-style device names to driver letters using the Disk Information Window (explained later). Windows users, just be aware that unless otherwise noted, the Linux conventions also apply to you.

Linux and macOS tend to use different names for devices. On Linux, it's quite common to have names like "/dev/sda" (first hard drive), "/dev/sdb" (second hard drive), and "/dev/sr0" (first optical drive). You might also see names like "/dev/sda1", which represents the first partition on the first hard drive. macOS, however, tends to call disks "/dev/disk0" (first disk in the system, usually the boot drive), "/dev/disk1" (could be a hard drive, USB drive, or optical drive), and "/dev/disk1s2" (second partition on the second drive). It's a bit easier to understand the Linux names. If you're finding this confusing, don't worry, because I will explain it more clearly later along with some of the other concepts. It's quite complicated.

Now for the really confusing bit. While you CAN read directly from these devices, you won't be able to understand what you're reading. This is where it becomes different from Windows. On Linux and macOS, pretty much everything is accessed as a file, including devices. So, essentially, when you read from, say, "/dev/disk0", you're actually reading data directly from the hard drive as if it were a file. In order to be able to use the drive in any meaningful way, it needs to have partitions and filesystems.