How can a partial image backup or restore be performed?

Solution 1:

Acronis - various versions, home & corporate, none free - can do this.

From their (outdated but still relevant) KB

Introduction

When you transfer a system to a hard drive that is larger or smaller than the original one, Acronis True Image allows you to create a new partition layout to fit the hard disk of a larger or smaller size.

It is possible to restore a disk image to a smaller drive if the smaller drive has enough space to accommodate the occupied space of the larger disk (e.g. if you have a 200 GB disk with 100 GB occupied space, you can transfer image of this disk to a 150 GB drive, but not to 80 GB disk).

Solution

Resizing all partitions proportionally during restore:

(!) This can be done only with a backup of an entire hard disk.

1. Create a backup of an entire hard disk that you want to restore to a larger or smaller one;
2. Boot the computer with the new hard disk from Acronis Bootable Media;
3. Restore the image;
4. All the partitions will be restored proportionally to fit in the new hard drive automatically.

Resizing all or separate partitions manually during restore:

1. Create a backup of entire hard disk or some partitions that you want to restore to a larger or smaller hard disk or partitions;
2. Boot the computer with the new hard disk from Acronis Bootable Media;
3. Restore the image. At the Partition or Disk to Restore step of Restore Data Wizard do not select and entire disk. Select a single partition and follow through the wizard. You will get a Restored Partition Size option, which you can adjust.

They also have an additional component [used to be at additional cost, now seems to be rolled into the product line] called Universal Restore, which allows restore to non-matching hardware - useful for porting to a new machine.

I have no affiliation to Acronis, I just use it myself & find it does what it claims.

Solution 2:

My initial searches on partial restore confirmed my previous understanding that restoring had to be to an equal or larger sized partition. That led to a focus on a method of partial partition imaging, a fruitless search, and this question. After @Tetsujin's answer, I dug deeper into partial restores, and it turns out there are some free solutions, including several mentioned in another question on Super User.

@harrymc's answer to a question on restoring to a different-sized drive (my search terms hadn't picked it up), mentions two free products, AOMEI Backupper and Paragon Backup and Recovery (the feature is described here), which both have this capability. I found AOMEI also recommended in an answer on another forum. There are also a couple of other non-free programs.

So if anyone else is looking at this problem from the same angle I was, this will serve as a second place on Super User to find the information. I never did find a way to create a partial image, which would be useful because it would save a lot of time.