iso or not ISO
 

Hello,

What is the REAL goal of an ISO file ?

Is it also used for linux for system recovery ?
In my opinion I would say "no" because everything is FILE under Linux :) !!

See you

It has nothing to do with Linux ISO Image Wiki.

It is an optical disk image format conforming to the International Standards Organization (ISO) 9660 standard.

ISO is a standard that covers thousands of things.

What we use for the term ISO is a somewhat standard way to create an optical disc. We also use it as a term for an image of disc in a special format.

When we say an ISO as in a file it is indeed a special file created by some program that is a clone of a disc. That disc may be of any form and state. You can't say it has to have this or that exactly.

We tend to download an ISO image and then either use it to burn a cd/dvd with an application NOT as a file but as an image of a disc. Or we can also do other things like use it to boot a virtual machine. Can mount it to a directory.


You already know you can't copy an iso file to a disc and get it to work correctly.

Like a zip file only in terms of difference and use. You may have a file indeed but you need to expand it to get it to work and be usable.

Usually the filesystem used with optical media like CDROM, DVD is ISO9660 filesystem. And popularly it is referred as short ISO. After ISO9660 came UDF filesystem.

Read Wikipedia article on ISO9660 filesystem for more info.

Actually, this works just fine:
The Debian jessie installation guide advises this method ;)
https://www.debian.org/releases/stab...copy-isohybrid

Didn't know you could use cp for that. I always used dd.

If you use cp you literally have a copy on your disk, if you use dd you create an image on the disk.
The two are totally different. ;)

(Edit: I think you can also use cat to put an image onto a disk.)

Try if for yourself -- it works in exactly the same way.

I am typing this in a system installed from an ISO image that was transferred to a USB stick with the `cp` command.

And yes, `cat` also works:

my specific context
 

" we can also do other things like use it to boot a virtual machine" --> that was my original context.

Is that different regarding iso of disc and the iso used for a VM ?

(naively yes)

thanks for help

VM's have a few ways to boot them. While we think of a VM as a real computer for most things, the vm application allows us to use a file instead of a physical drive. One can select an iso image and boot to it in a vm. Actually some loaders can boot directly to some iso images too.

"# cp example.iso /dev/sdX
# sync"

Make note that I said DISC and not DISK. They are two different things.

It definitely works.

okay WHAT contains an iso file ?
(file system ?)

type of format

Nothing, an ISO file IS a file. One file. Sure it sits within a file system, and you can download one and then store it somewhere.

What you really do with it, is one thing, which is to use that ISO image to create a full disk which matches the "contents" of the ISO image.

In short, the ISO file is one file which represents a disk image. You take that image and program or burn it to a disk, such as a CD/DVD or USB thumbstick and when the programming or burning is complete the resultant information on the target disk is not one ISO file, but a collection of files, per the intent of the original ISO file/archive creator.

The most common case here is that an ISO image contains an entire boot-able Linux distribution for ready use as a live boot distribution as well as boot disk for installing Linux onto your system.

When in Windows or Linux desktop the easiest way to "burn" an ISO image to a CD/DVD is to use CD burning software and when it asks for your original or "from" image, you tell it the ISO file, and when it asks for the copy, or "to" location, you tell it the CD/DVD drive, or USB stick drive if the software can manage that particular case.

There are other ways to copy an ISO image to a disk.

Note also that you can just directly "copy" an ISO file from disk to disk and that just copies the ISO file. (Excepting the special case of using the dd command - an advanced concept if you're a total newbie)

A common mistake is that someone new to the concept gets an ISO file, copies it as an ISO file to another disk, then tries to boot with that to find that the ISO file itself will not boot, and what they had to do was burn that as an image, which would then extract the contained files instead of just placing the ISO image onto the disk.

And it is perfectly fine to "have" an ISO file somewhere on a larger disk. For instance I've downloaded several versions of distributions and happen to have those ISO files sitting in my Download folder. It's merely a question of when I choose to extract those files and program to a boot media; otherwise they just sit there.

Just to clarify, there is the ISO and then there is an ISO File. ISO by itself is a disk format, where as an ISO file is the contents copied from an ISO format. This is why an ISO file can be placed on a disk of some other format and then mounted as a separate virtual drive.