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This is something that has happened to me more than a few times and I finally decided to ask, as I cannot find any information on it.

I was downloading two different Linux distros, each were ~1.8GB .ISOs. I tried to write them to a 2GB USB stick and it fails saying the disk is not big enough. I tried using both Rufus and Etcher to write the files, with the same result.

I am assuming these "minimal" ISOs, which are all under 2GB, are designed to be small enough to fit on a 2GB USB stick, or am I wrong?

Keltari
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1 Answers1

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In non DD mode, Rufus will convert from one file system to another, which means that there's no guarantee that what occupies less than 2 GB of content with one file system will also occupy less than 2 GB in the other. There are many elements that can make files take more space when copied from one file system to another, such a cluster size, fragmentation and so on.

Also, when Windows reports that an ISO is 1.8 GB, it means that it occupies about 1.8 x 1024 x 1024 x 1024 bytes = 1932735284 bytes of disk space. That's because Windows uses the historical definition of a kilobyte which is 1024 bytes. But when a manufacturer says a flash drive is 2 GB, it means that it can accommodate up to 2 x 1000 x 1000 x 1000 = 2000000000 bytes, because drive manufacturers use their own smaller definition of a kilobyte in order to make their drives look larger to unsuspecting consumers. So, in "manufacturer units", there's a difference of about 0.068 GB rather than 0.2 GB between the size of your drive and the size of your ISO, which isn't that much.

As such, it isn't surprising that the content from your 1.8 GB ISO may not fit on a "2 GB" flash drive when written in ISO mode. To make it fit, you may have to select DD mode when Rufus prompts you.

Akeo
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