Does an image backup need to end in .img?

I'm using pv on Cygwin to backup an SD card to an image. I'm using pv over dd primarily for the ETA percentage that it offers by default.

pv /dev/sdc > /cygdrive/B/Users/Hashim/Desktop/SDBackup

My question is whether SDBackup will be a sufficient image that I can then use dd or pv to restore from to the SD card, or whether I should have specified SDBackup.img instead?

In other words, do dd/bash/Cygwin need the .img extension? It's always been my understanding that they don't, but I've recently been confused by other sources that include the .img. Am I correct in suspecting they do this purely for compatibility reasons so that the resulting image can be used with other utilities, or is there more to it?

Hashim

Posted 2018-02-02T00:57:15.867

Reputation: 6 967

I don’t think the .img extension will do anything magical. It should simply be there as a convenience for you to be able to recognize it later on if/when you come across the file yet don’t immediately recall what it is. – JakeGould – 2018-02-02T03:46:14.360

Answers

The filename is entirely arbitrary. Using .img is a useful convention which may be recognised by some other programs, but DD does not care.

While it's by no means required, putting an extension is a good idea as generally an extension differentiates a file from a directory (again, a convention, OS's do not require it)

davidgo

Posted 2018-02-02T00:57:15.867

Reputation: 49 152

1Accepted, but I think it may be more accurate to say that UNIX-based OSes don't require it, as Windows will render files without extensions unusable. – Hashim – 2018-02-02T22:36:59.427

@Hashim - I confess my expertise lie outside Windows, but it I'm fairly sure you can manipulate files without extensions fine in Windows - as long as you don't expect a program to recognise what type of file it is. The NTFS and FAT filesystems have on problem differentiating between files and directories where files are without extensions. To a lesser degree the same can be said of Linux - save that Linux can read the first line to see how to execute it (if it's set executable) – davidgo – 2018-02-03T00:18:46.677