How do I restore from a backup?

I'll start by splitting backups into two broad category: file and image.

Restoring File Backups

File backups are just that - backups of selected files. It can be many files, it might even be nearly all files, but it's never a backup that can be used to restore a machine completely. The primary purpose of file-based backups is to be able to restore or recover:

• any of those files, but only those files
• to a working system

For example: let's say you mistakenly delete, overwrite or somehow trash the file containing your bookkeeping records. You can recover that file from a file-based backup.

The biggest issue with recovering from a file-based backup is getting it out of whatever storage method your backup program uses. This is where we can't really dive into specifics, since each program might use its own.

Some programs simply copy files - literally. Restoring the file is nothing more than locating the backup copy of the file on some storage medium, such as the external hard disk it was backed up to, and copying it back.

More commonly backup programs create large backup archives in single files that contain the backed up files in some compressed conglomeration. In those cases, you'll need to run the same backup program which would then have a restore or browse option to let you locate and extract the file or files you're looking for. The key is that you'll need that backup program to be able to access the contents of the backup archive. (Caveat: in most cases. Some backup programs actually use common formats like "zip" files for their backups, so you might be able to use other tools. Not many do, so make sure you're prepared in any case.)

But that's all it really boils down to for restoring files from a file-based backup: locate the backup and use the original backup programs browse functionality to locate and extract the files you're looking for.

Restoring Image Backups

Image backups backup an image of your hard drive. (I'm lumping both sector-based and file-system based image backups into this category, since for the purposes of this discussion they're the same.)

There are two approaches to restoring a complete image:

• An image can be restored to a secondary hard disk on a working system. That means you can't restore it to the hard disk that's in use by the system (typically C:), but you can restore it to some other hard disk installed on the machine. In this case, you typically just run the backup software and use a restore function that it should provide.

• An image can be restored to the primary hard disk on any system by booting from some other media. In other words, in order to perform a complete restoration of your primary hard drive (again, typically C:), you have to boot from something else. Most image backup programs also include the ability to create a bootable restore disk for just this purpose.

It's that last scenario that is both the most powerful, and the most confusing. And the thing that most people don't prepare for.

Preparation is actually fairly simple. Before you ever need your backup - ideally when you set up your periodic backups in the first place - make sure you have or create the restore boot disk that your backup program should provide. Save it in a safe place so that if you ever need to perform a restore, you'll have it ready.

Note that this is not the same as the disk containing your actual backup. That disk is rarely bootable by itself. The bootable media is a separate disk - often just a single CD - that you have or create once and keep somewhere safe.

When your hard drive needs to be completely restored from the backup image you would:

• Boot your machine from the bootable restoration media.

• Attach or locate your backed up data - perhaps by attaching the external hard drive you'd been backing up to.

• Run the backup program which was on the bootable media and use its restore function to restore data from your backup drive to the hard disk in the machine.

Again, conceptually simple, but it's very easy to overlook that initial step.

What's unique about restoring an image backup is that you don't need to have anything installed on the machine's hard drive; it can be a brand new and completely empty hard drive. You boot from a CD, and then restore a backup image to that new hard drive.

Restoring Files from an Image

Sometimes even with an image-based backup you just want to restore a file.

The good news here is that almost all image-based backup programs will also let you view the contents of an image backup and extract from it just the file or files you need. In many ways this is just like a file-based backup. Just fire up the backup program and use its restore or browse features to examine the contents of one of your backups to locate and restore your file.

An image-based backup can be considered a superset of a file-based backup; it has everything that the file-based backup has, and more. The cost? The size of the resulting backup, and perhaps the amount of time it takes to perform either the backup or restore.

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No article on backing up would be complete without reminding you that all of this is moot if you're not actually backing up.

Back up.

Back up regularly, so that when the time comes you'll have some of the options above to choose from as you successfully restore your data.