Loop Device – What is a Loop Device When Mounting?

greplinuxloop-devicemount

I am mounting an ISO file, and looking at this tutorial. They use the command:

$ mount -o loop disk1.iso /mnt/disk

I'm trying to understand the use of -o loop. I have two questions:

  1. When I look at the long man page for mount, it takes time to find that -o option. If I do man mount | grep "-o" I get an error, and when I look in the file I do not find any info that "loop" is a command text for option -o. Where is that documented?

  2. Also, what is the "loop device" concept for mounting?

Best Answer

A loop device is a pseudo ("fake") device (actually just a file) that acts as a block-based device. You want to mount a file disk1.iso that will act as an entire filesystem, so you use loop.

The -o is short for --options.

And the last thing, if you want to search for "-o" you need to escape the '-'.

Try:

man mount | grep "\-o"
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