“Copy my USB stick” can mean three quite different things. Pick the wrong one and you might end up with a copy that looks complete but won’t actually start a Raspberry Pi or boot a PC. Here’s what each one really copies.
First: what’s actually on a drive
A USB stick or SD card holds more than the files you see in File Explorer:
- a partition table: a small map at the start of the drive saying how it’s divided up;
- one or more partitions, each formatted with a filesystem. Windows can read some of them (FAT32, exFAT, NTFS). Others, like the Linux partitions on a Raspberry Pi card, it can’t read at all;
- boot code and other bits that live outside any file, which is what makes a drive bootable.
Copying files only gets the part Windows can see. Imaging and cloning get everything.
Copying files
Dragging files from the drive to your PC in File Explorer.
- Copies: the files and folders in partitions Windows can read.
- Misses: partitions Windows can’t read, the partition table, boot code, and deleted-but-recoverable data.
- Good for: photos, documents, music. Anything where you care about the files, not the drive.
- Not good for: Raspberry Pi cards, boot sticks, or anything that needs to start something.
Imaging (a backup file)
Reading the whole drive, from its first byte to its last, into a single file on your PC. In DiskSnap that’s Backup, and the file is a .dsnap. Putting it back onto a drive is Restore.
- Copies: everything: every partition, the partition table and the boot code.
- Leaves you with: a file you can keep, copy to another disk, and restore as many times as you like. You can keep several, from different dates.
- Needs: space on your PC. Restoring needs a drive at least as big as the original.
- Good for: a safety net before you change something, keeping a known-good Raspberry Pi setup, or archiving a drive before reusing it.
How to: Back up a USB stick or SD card, then Restore a DiskSnap backup.
Cloning
Copying the whole drive straight onto another drive, with no file in between. In DiskSnap that’s Clone.
- Copies: everything, the same as imaging.
- Leaves you with: a second drive that’s a copy of the first, and no file on your PC.
- Needs: both drives plugged in at once. The target must be at least as big as the source, and it is completely erased.
- Good for: making a spare card or stick quickly, when you don’t need a copy on your PC.
How to: Clone a USB stick or SD card.
At a glance
| Copy files | Image (Backup) | Clone | |
|---|---|---|---|
| Copies partitions Windows can’t read | No | Yes | Yes |
| Result still boots | No | Yes, once restored | Yes |
| Leaves a file on your PC | Yes, the files | Yes, one .dsnap | No |
| Erases another drive | No | Only when you restore | Yes, the target |
| The original drive is | Read | Only read | Only read |
And Make Bootable?
DiskSnap’s Make Bootable is imaging in reverse, from someone else’s image. It takes a downloaded image or ISO, such as Ubuntu, and writes it onto a drive, so the drive can start a computer. See Make a bootable Ubuntu USB.
So which do I need?
- I just want my photos off an SD card: copy the files.
- I want to be able to undo whatever I’m about to do to this card: make a backup (image).
- I want a spare of this working card, right now: clone it. Or make a backup and restore it onto the spare, which also leaves you a file to keep.
